AI Trajectory

null

{
  "EnableConfigs": null,
  "FocusSymbols": [],
  "Reasoning": "The patch modifies the usage of `hmm_range_fault_unlocked_timeout` in three hardware-specific drivers: AMD XDNA (`drivers/accel/amdxdna`), Intel Xe (`drivers/gpu/drm/drm_gpusvm.c`, which is only used by `xe`), and Nouveau (`drivers/gpu/drm/nouveau`). These drivers require specific physical hardware (AMD XDNA NPU, Intel Xe GPU, NVIDIA GPU) to initialize and expose their interfaces. Since syzkaller operates in virtualized environments (GCE/QEMU) without this specific hardware or software emulation for them, these code paths are impossible to reach and fuzz.",
  "WorthFuzzing": false
}

null

{
  "PatchDiff": "commit b5f2d8d7927f92087a437f0182e7ff1a97f15028\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Wed Jul 15 08:03:22 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/Documentation/mm/hmm.rst b/Documentation/mm/hmm.rst\nindex 5c88d2cf081833..fc1b8dc198250e 100644\n--- a/Documentation/mm/hmm.rst\n+++ b/Documentation/mm/hmm.rst\n@@ -206,7 +206,7 @@ The usage pattern is::\n           goto out_put;\n \n       take_lock(driver-\u003eupdate);\n-      if (mmu_interval_read_retry(\u0026interval_sub, range.notifier_seq)) {\n+      if (mmu_interval_read_retry(range.notifier, range.notifier_seq)) {\n           release_lock(driver-\u003eupdate);\n           goto again;\n       }\n@@ -225,7 +225,8 @@ The usage pattern is::\n The driver-\u003eupdate lock is the same lock that the driver takes inside its\n invalidate() callback. That lock must be held before calling\n mmu_interval_read_retry() to avoid any race with a concurrent CPU page table\n-update.\n+update. The retry check must use the same notifier and sequence number stored\n+in ``range`` by ``hmm_range_fault_unlocked_timeout()``.\n \n Holding the mmap lock across HMM faults\n =======================================\ndiff --git a/drivers/accel/amdxdna/aie2_ctx.c b/drivers/accel/amdxdna/aie2_ctx.c\nindex 548ba4315554ff..21f2817751f9e7 100644\n--- a/drivers/accel/amdxdna/aie2_ctx.c\n+++ b/drivers/accel/amdxdna/aie2_ctx.c\n@@ -1037,7 +1037,7 @@ static int aie2_populate_range(struct amdxdna_gem_obj *abo)\n \tbool found;\n \tint ret;\n \n-\ttimeout = jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);\n+\ttimeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);\n again:\n \tfound = false;\n \tdown_write(\u0026xdna-\u003enotifier_lock);\n@@ -1062,13 +1062,9 @@ static int aie2_populate_range(struct amdxdna_gem_obj *abo)\n \t\treturn -EFAULT;\n \t}\n \n-\tret = hmm_range_fault_unlocked_timeout(\u0026mapp-\u003erange,\n-\t\t\tmax_t(long, timeout - jiffies, 1));\n-\tif (ret) {\n-\t\tif (ret == -EBUSY)\n-\t\t\tret = -ETIME;\n+\tret = hmm_range_fault_unlocked_timeout(\u0026mapp-\u003erange, timeout);\n+\tif (ret)\n \t\tgoto put_mm;\n-\t}\n \n \tdown_write(\u0026xdna-\u003enotifier_lock);\n \tif (mmu_interval_read_retry(\u0026mapp-\u003enotifier, mapp-\u003erange.notifier_seq)) {\n@@ -1086,7 +1082,7 @@ static int aie2_populate_range(struct amdxdna_gem_obj *abo)\n put_mm:\n \tamdxdna_umap_put(mapp);\n \tmmput(mm);\n-\treturn ret;\n+\treturn ret == -EBUSY ? -ETIME : ret;\n }\n \n int aie2_cmd_submit(struct amdxdna_hwctx *hwctx, struct amdxdna_sched_job *job, u64 *seq)\ndiff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c\nindex b8f2dd9982f53c..76e8a0028c7fc9 100644\n--- a/drivers/gpu/drm/drm_gpusvm.c\n+++ b/drivers/gpu/drm/drm_gpusvm.c\n@@ -852,8 +852,7 @@ enum drm_gpusvm_scan_result drm_gpusvm_scan_mm(struct drm_gpusvm_range *range,\n \t\t.end = end,\n \t\t.dev_private_owner = dev_private_owner,\n \t};\n-\tunsigned long timeout =\n-\t\tjiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);\n+\tunsigned long timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);\n \tenum drm_gpusvm_scan_result state = DRM_GPUSVM_SCAN_UNPOPULATED, new_state;\n \tunsigned long *pfns;\n \tunsigned long npages = npages_in_range(start, end);\n@@ -867,8 +866,7 @@ enum drm_gpusvm_scan_result drm_gpusvm_scan_mm(struct drm_gpusvm_range *range,\n \thmm_range.hmm_pfns = pfns;\n \n retry:\n-\terr = hmm_range_fault_unlocked_timeout(\u0026hmm_range,\n-\t\t\t\t\t       max(timeout - jiffies, 1L));\n+\terr = hmm_range_fault_unlocked_timeout(\u0026hmm_range, timeout);\n \tif (err)\n \t\tgoto err_free;\n \n@@ -1459,8 +1457,7 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,\n \t\t.dev_private_owner = ctx-\u003edevice_private_page_owner,\n \t};\n \tvoid *zdd;\n-\tunsigned long timeout =\n-\t\tjiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);\n+\tunsigned long timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);\n \tunsigned long i, j;\n \tunsigned long npages = npages_in_range(pages_start, pages_end);\n \tunsigned long num_dma_mapped;\n@@ -1478,9 +1475,6 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,\n \t\treturn -EINVAL;\n \n retry:\n-\tif (time_after(jiffies, timeout))\n-\t\treturn -EBUSY;\n-\n \thmm_range.notifier_seq = mmu_interval_read_begin(notifier);\n \tif (drm_gpusvm_pages_valid_unlocked(gpusvm, svm_pages))\n \t\tgoto set_seqno;\n@@ -1495,8 +1489,7 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,\n \t}\n \n \thmm_range.hmm_pfns = pfns;\n-\terr = hmm_range_fault_unlocked_timeout(\u0026hmm_range,\n-\t\t\t\tmax_t(long, timeout - jiffies, 1));\n+\terr = hmm_range_fault_unlocked_timeout(\u0026hmm_range, timeout);\n \tmmput(mm);\n \tif (err)\n \t\tgoto err_free;\n@@ -1718,8 +1711,7 @@ int drm_gpusvm_range_evict(struct drm_gpusvm *gpusvm,\n \t\t.end = drm_gpusvm_range_end(range),\n \t\t.dev_private_owner = NULL,\n \t};\n-\tunsigned long timeout =\n-\t\tjiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);\n+\tunsigned long timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);\n \tunsigned long *pfns;\n \tunsigned long npages = npages_in_range(drm_gpusvm_range_start(range),\n \t\t\t\t\t       drm_gpusvm_range_end(range));\n@@ -1734,8 +1726,7 @@ int drm_gpusvm_range_evict(struct drm_gpusvm *gpusvm,\n \t\treturn -ENOMEM;\n \n \thmm_range.hmm_pfns = pfns;\n-\terr = hmm_range_fault_unlocked_timeout(\u0026hmm_range,\n-\t\t\t\tmax_t(long, timeout - jiffies, 1));\n+\terr = hmm_range_fault_unlocked_timeout(\u0026hmm_range, timeout);\n \n \tkvfree(pfns);\n \tmmput(mm);\ndiff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c\nindex 4cfb6eb7c7715a..58735446d7832c 100644\n--- a/drivers/gpu/drm/nouveau/nouveau_svm.c\n+++ b/drivers/gpu/drm/nouveau/nouveau_svm.c\n@@ -678,14 +678,20 @@ static int nouveau_range_fault(struct nouveau_svmm *svmm,\n \trange.end = notifier-\u003enotifier.interval_tree.last + 1;\n \n \twhile (true) {\n-\t\tif (time_after(jiffies, timeout)) {\n+\t\tlong remaining = timeout - jiffies;\n+\n+\t\t/*\n+\t\t * The HMM timeout only bounds retries while HMM is walking and\n+\t\t * faulting the range. This fault is handled by a kernel worker,\n+\t\t * so fatal signals from the faulting process cannot stop an\n+\t\t * endless stream of invalidations here.\n+\t\t */\n+\t\tif (time_after_eq(jiffies, timeout)) {\n \t\t\tret = -EBUSY;\n \t\t\tgoto out;\n \t\t}\n \n-\t\tret = hmm_range_fault_unlocked_timeout(\u0026range,\n-\t\t\t\t\t\t       max(timeout - jiffies,\n-\t\t\t\t\t\t\t   1L));\n+\t\tret = hmm_range_fault_unlocked_timeout(\u0026range, remaining);\n \t\tif (ret)\n \t\t\tgoto out;\n \n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": null,
  "FocusSymbols": [],
  "Reasoning": "The patch modifies the usage of `hmm_range_fault_unlocked_timeout` in three hardware-specific drivers: AMD XDNA (`drivers/accel/amdxdna`), Intel Xe (`drivers/gpu/drm/drm_gpusvm.c`, which is only used by `xe`), and Nouveau (`drivers/gpu/drm/nouveau`). These drivers require specific physical hardware (AMD XDNA NPU, Intel Xe GPU, NVIDIA GPU) to initialize and expose their interfaces. Since syzkaller operates in virtualized environments (GCE/QEMU) without this specific hardware or software emulation for them, these code paths are impossible to reach and fuzz.",
  "WorthFuzzing": false
}

You are an expert Linux kernel maintainer.
Your job is to review a provided patch series and determine
if it makes functional changes to the kernel that should be fuzzed.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively
use your code access tools to examine the actual source code and confirm any assumptions.

Return WorthFuzzing=false if the patch only contains:
- Modifications to Documentation/, Kconfig files, or code comments.
- Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints.
- Changes to numeric constants or macros that do not functionally alter execution flow.
- Code paths that are impossible to reach in virtualized environments like GCE or QEMU,
even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim).

If it modifies reachable core kernel logic, drivers, or architectures, use your code search
tools to verify the code can be executed, then return WorthFuzzing=true.

When returning WorthFuzzing=true, you MUST ALSO:
1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols.
   Avoid listing generic hot-path functions to prevent skewed test distributions.
2. Identify any specific CONFIG_ options required to properly test this new/modified feature.
   Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions.
   Do not list too generic configs (we already have them enabled). Only list those that
   specifically cover the modified code. List them in the EnableConfigs output array,
   and DO NOT add a 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4").
Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

For your convenience, here is the diff of the changes:
commit b5f2d8d7927f92087a437f0182e7ff1a97f15028
Author: syz-cluster <triage@syzkaller.com>
Date:   Wed Jul 15 08:03:22 2026 +0000

    syz-cluster: applied patch under review

diff --git a/Documentation/mm/hmm.rst b/Documentation/mm/hmm.rst
index 5c88d2cf081833..fc1b8dc198250e 100644
--- a/Documentation/mm/hmm.rst
+++ b/Documentation/mm/hmm.rst
@@ -206,7 +206,7 @@ The usage pattern is::
           goto out_put;
 
       take_lock(driver->update);
-      if (mmu_interval_read_retry(&interval_sub, range.notifier_seq)) {
+      if (mmu_interval_read_retry(range.notifier, range.notifier_seq)) {
           release_lock(driver->update);
           goto again;
       }
@@ -225,7 +225,8 @@ The usage pattern is::
 The driver->update lock is the same lock that the driver takes inside its
 invalidate() callback. That lock must be held before calling
 mmu_interval_read_retry() to avoid any race with a concurrent CPU page table
-update.
+update. The retry check must use the same notifier and sequence number stored
+in ``range`` by ``hmm_range_fault_unlocked_timeout()``.
 
 Holding the mmap lock across HMM faults
 =======================================
diff --git a/drivers/accel/amdxdna/aie2_ctx.c b/drivers/accel/amdxdna/aie2_ctx.c
index 548ba4315554ff..21f2817751f9e7 100644
--- a/drivers/accel/amdxdna/aie2_ctx.c
+++ b/drivers/accel/amdxdna/aie2_ctx.c
@@ -1037,7 +1037,7 @@ static int aie2_populate_range(struct amdxdna_gem_obj *abo)
 	bool found;
 	int ret;
 
-	timeout = jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
+	timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
 again:
 	found = false;
 	down_write(&xdna->notifier_lock);
@@ -1062,13 +1062,9 @@ static int aie2_populate_range(struct amdxdna_gem_obj *abo)
 		return -EFAULT;
 	}
 
-	ret = hmm_range_fault_unlocked_timeout(&mapp->range,
-			max_t(long, timeout - jiffies, 1));
-	if (ret) {
-		if (ret == -EBUSY)
-			ret = -ETIME;
+	ret = hmm_range_fault_unlocked_timeout(&mapp->range, timeout);
+	if (ret)
 		goto put_mm;
-	}
 
 	down_write(&xdna->notifier_lock);
 	if (mmu_interval_read_retry(&mapp->notifier, mapp->range.notifier_seq)) {
@@ -1086,7 +1082,7 @@ static int aie2_populate_range(struct amdxdna_gem_obj *abo)
 put_mm:
 	amdxdna_umap_put(mapp);
 	mmput(mm);
-	return ret;
+	return ret == -EBUSY ? -ETIME : ret;
 }
 
 int aie2_cmd_submit(struct amdxdna_hwctx *hwctx, struct amdxdna_sched_job *job, u64 *seq)
diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
index b8f2dd9982f53c..76e8a0028c7fc9 100644
--- a/drivers/gpu/drm/drm_gpusvm.c
+++ b/drivers/gpu/drm/drm_gpusvm.c
@@ -852,8 +852,7 @@ enum drm_gpusvm_scan_result drm_gpusvm_scan_mm(struct drm_gpusvm_range *range,
 		.end = end,
 		.dev_private_owner = dev_private_owner,
 	};
-	unsigned long timeout =
-		jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
+	unsigned long timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
 	enum drm_gpusvm_scan_result state = DRM_GPUSVM_SCAN_UNPOPULATED, new_state;
 	unsigned long *pfns;
 	unsigned long npages = npages_in_range(start, end);
@@ -867,8 +866,7 @@ enum drm_gpusvm_scan_result drm_gpusvm_scan_mm(struct drm_gpusvm_range *range,
 	hmm_range.hmm_pfns = pfns;
 
 retry:
-	err = hmm_range_fault_unlocked_timeout(&hmm_range,
-					       max(timeout - jiffies, 1L));
+	err = hmm_range_fault_unlocked_timeout(&hmm_range, timeout);
 	if (err)
 		goto err_free;
 
@@ -1459,8 +1457,7 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
 		.dev_private_owner = ctx->device_private_page_owner,
 	};
 	void *zdd;
-	unsigned long timeout =
-		jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
+	unsigned long timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
 	unsigned long i, j;
 	unsigned long npages = npages_in_range(pages_start, pages_end);
 	unsigned long num_dma_mapped;
@@ -1478,9 +1475,6 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
 		return -EINVAL;
 
 retry:
-	if (time_after(jiffies, timeout))
-		return -EBUSY;
-
 	hmm_range.notifier_seq = mmu_interval_read_begin(notifier);
 	if (drm_gpusvm_pages_valid_unlocked(gpusvm, svm_pages))
 		goto set_seqno;
@@ -1495,8 +1489,7 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
 	}
 
 	hmm_range.hmm_pfns = pfns;
-	err = hmm_range_fault_unlocked_timeout(&hmm_range,
-				max_t(long, timeout - jiffies, 1));
+	err = hmm_range_fault_unlocked_timeout(&hmm_range, timeout);
 	mmput(mm);
 	if (err)
 		goto err_free;
@@ -1718,8 +1711,7 @@ int drm_gpusvm_range_evict(struct drm_gpusvm *gpusvm,
 		.end = drm_gpusvm_range_end(range),
 		.dev_private_owner = NULL,
 	};
-	unsigned long timeout =
-		jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
+	unsigned long timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
 	unsigned long *pfns;
 	unsigned long npages = npages_in_range(drm_gpusvm_range_start(range),
 					       drm_gpusvm_range_end(range));
@@ -1734,8 +1726,7 @@ int drm_gpusvm_range_evict(struct drm_gpusvm *gpusvm,
 		return -ENOMEM;
 
 	hmm_range.hmm_pfns = pfns;
-	err = hmm_range_fault_unlocked_timeout(&hmm_range,
-				max_t(long, timeout - jiffies, 1));
+	err = hmm_range_fault_unlocked_timeout(&hmm_range, timeout);
 
 	kvfree(pfns);
 	mmput(mm);
diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
index 4cfb6eb7c7715a..58735446d7832c 100644
--- a/drivers/gpu/drm/nouveau/nouveau_svm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
@@ -678,14 +678,20 @@ static int nouveau_range_fault(struct nouveau_svmm *svmm,
 	range.end = notifier->notifier.interval_tree.last + 1;
 
 	while (true) {
-		if (time_after(jiffies, timeout)) {
+		long remaining = timeout - jiffies;
+
+		/*
+		 * The HMM timeout only bounds retries while HMM is walking and
+		 * faulting the range. This fault is handled by a kernel worker,
+		 * so fatal signals from the faulting process cannot stop an
+		 * endless stream of invalidations here.
+		 */
+		if (time_after_eq(jiffies, timeout)) {
 			ret = -EBUSY;
 			goto out;
 		}
 
-		ret = hmm_range_fault_unlocked_timeout(&range,
-						       max(timeout - jiffies,
-							   1L));
+		ret = hmm_range_fault_unlocked_timeout(&range, remaining);
 		if (ret)
 			goto out;
 

gemini-3.1-pro-preview

null

null

							input: 4119
							output: 24
							thoughts: 448
						

**Analyzing the Timeout Change in HMM Range Fault Handling**

Okay, so I'm looking at this patch and it appears to be modifying how `hmm_range_fault_unlocked_timeout` is called across a few drivers: amdxdna, drm_gpusvm, and nouveau_svm. The key change seems to be how the `timeout` argument is handled. It's moving from being an absolute jiffies value, or a remaining time calculation, to a *relative* timeout. Initially, I thought it was just passing the `timeout` variable which is now initialized as `msecs_to_jiffies(...)`. Let me dig a little deeper.

Specifically, in `aie2_ctx.c`, the diff shows:

```c
-	timeout = jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
+	timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
...
-	ret = hmm_range_fault_unlocked_timeout(&mapp->range,
-			max_t(long, timeout - jiffies, 1));
-	if (ret) {
-		if (ret == -EBUSY)
-			ret = -ETIME;
+	ret = hmm_range_fault_unlocked_timeout(&mapp->range, timeout);
+	if (ret)
 		goto put_mm;
-	}
```

Okay, so the calculation of the absolute timeout is gone and now we're just passing the result of `msecs_to_jiffies()`. But wait a second... is `hmm_range_fault_unlocked_timeout` designed to accept a relative timeout now? Or did that change in a previous or separate patch? The diff itself doesn't show the function definition changing, which is a bit odd. Perhaps the function was already changed to handle relative timeouts, and this patch simply aligns the calling convention? Let me look at some other diffs. Ah, there's a related change in `hmm.rst` which removes the use of `jiffies` in a comparison:

```c
-      if (mmu_interval_read_retry(&interval_sub, range.notifier_seq)) {
+      if (mmu_interval_read_retry(range.notifier, range.notifier_seq)) {
```

Still nothing about the `hmm_range_fault_unlocked_timeout` definition. Let's go look at the function definition itself, and be sure we have the full picture.

{
  "Expression": "hmm_range_fault_unlocked_timeout"
}

{
  "Output": "Documentation/mm/hmm.rst=160=normal interface is::\nDocumentation/mm/hmm.rst-161-\nDocumentation/mm/hmm.rst:162:  int hmm_range_fault_unlocked_timeout(struct hmm_range *range,\nDocumentation/mm/hmm.rst-163-                                       unsigned long timeout);\n--\nDocumentation/mm/hmm.rst=169=The caller must not hold ``mmap_read_lock`` before the call.\nDocumentation/mm/hmm.rst:170:``hmm_range_fault_unlocked_timeout()`` takes the mmap read lock internally and\nDocumentation/mm/hmm.rst-171-allows ``handle_mm_fault()`` to drop it during fault handling. This is required\n--\nDocumentation/mm/hmm.rst=186=The usage pattern is::\n--\nDocumentation/mm/hmm.rst-203- again:\nDocumentation/mm/hmm.rst:204:      ret = hmm_range_fault_unlocked_timeout(\u0026range, timeout);\nDocumentation/mm/hmm.rst-205-      if (ret)\n--\nDocumentation/mm/hmm.rst=228=update. The retry check must use the same notifier and sequence number stored\nDocumentation/mm/hmm.rst:229:in ``range`` by ``hmm_range_fault_unlocked_timeout()``.\nDocumentation/mm/hmm.rst-230-\nDocumentation/mm/hmm.rst=231=Holding the mmap lock across HMM faults\n--\nDocumentation/mm/hmm.rst-233-\nDocumentation/mm/hmm.rst:234:Most callers should use ``hmm_range_fault_unlocked_timeout()``. If a driver\nDocumentation/mm/hmm.rst-235-really needs to hold the mmap lock across work outside HMM, it can use::\n--\nDocumentation/mm/hmm.rst=240=interface cannot support VMAs whose fault handlers need to drop the mmap lock.\nDocumentation/mm/hmm.rst:241:New callers should prefer ``hmm_range_fault_unlocked_timeout()`` unless they\nDocumentation/mm/hmm.rst-242-have a specific requirement to keep the mmap lock held across the call.\n--\ndrivers/accel/amdxdna/aie2_ctx.c=1031=static int aie2_populate_range(struct amdxdna_gem_obj *abo)\n--\ndrivers/accel/amdxdna/aie2_ctx.c-1064-\ndrivers/accel/amdxdna/aie2_ctx.c:1065:\tret = hmm_range_fault_unlocked_timeout(\u0026mapp-\u003erange, timeout);\ndrivers/accel/amdxdna/aie2_ctx.c-1066-\tif (ret)\n--\ndrivers/gpu/drm/drm_gpusvm.c=841=enum drm_gpusvm_scan_result drm_gpusvm_scan_mm(struct drm_gpusvm_range *range,\n--\ndrivers/gpu/drm/drm_gpusvm.c-868-retry:\ndrivers/gpu/drm/drm_gpusvm.c:869:\terr = hmm_range_fault_unlocked_timeout(\u0026hmm_range, timeout);\ndrivers/gpu/drm/drm_gpusvm.c-870-\tif (err)\n--\ndrivers/gpu/drm/drm_gpusvm.c=1444=int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,\n--\ndrivers/gpu/drm/drm_gpusvm.c-1491-\thmm_range.hmm_pfns = pfns;\ndrivers/gpu/drm/drm_gpusvm.c:1492:\terr = hmm_range_fault_unlocked_timeout(\u0026hmm_range, timeout);\ndrivers/gpu/drm/drm_gpusvm.c-1493-\tmmput(mm);\n--\ndrivers/gpu/drm/drm_gpusvm.c=1703=int drm_gpusvm_range_evict(struct drm_gpusvm *gpusvm,\n--\ndrivers/gpu/drm/drm_gpusvm.c-1728-\thmm_range.hmm_pfns = pfns;\ndrivers/gpu/drm/drm_gpusvm.c:1729:\terr = hmm_range_fault_unlocked_timeout(\u0026hmm_range, timeout);\ndrivers/gpu/drm/drm_gpusvm.c-1730-\n--\ndrivers/gpu/drm/nouveau/nouveau_svm.c=652=static int nouveau_range_fault(struct nouveau_svmm *svmm,\n--\ndrivers/gpu/drm/nouveau/nouveau_svm.c-693-\ndrivers/gpu/drm/nouveau/nouveau_svm.c:694:\t\tret = hmm_range_fault_unlocked_timeout(\u0026range, remaining);\ndrivers/gpu/drm/nouveau/nouveau_svm.c-695-\t\tif (ret)\n--\ndrivers/hv/mshv_regions.c=396=static int mshv_region_range_fault(struct mshv_mem_region *region,\n--\ndrivers/hv/mshv_regions.c-415-again:\ndrivers/hv/mshv_regions.c:416:\tret = hmm_range_fault_unlocked_timeout(\u0026range, 0);\ndrivers/hv/mshv_regions.c-417-\tif (ret)\n--\ndrivers/infiniband/core/umem_odp.c=324=int ib_umem_odp_map_dma_and_lock(struct ib_umem_odp *umem_odp, u64 user_virt,\n--\ndrivers/infiniband/core/umem_odp.c-368-retry:\ndrivers/infiniband/core/umem_odp.c:369:\tret = hmm_range_fault_unlocked_timeout(\u0026range, timeout);\ndrivers/infiniband/core/umem_odp.c-370-\tif (unlikely(ret))\n--\ninclude/linux/hmm.h=125=int hmm_range_fault(struct hmm_range *range);\ninclude/linux/hmm.h:126:int hmm_range_fault_unlocked_timeout(struct hmm_range *range,\ninclude/linux/hmm.h-127-\t\t\t\t     unsigned long timeout);\n--\nlib/test_hmm.c=392=static int dmirror_range_fault_unlocked(struct dmirror *dmirror,\n--\nlib/test_hmm.c-398-\twhile (true) {\nlib/test_hmm.c:399:\t\tret = hmm_range_fault_unlocked_timeout(range, timeout);\nlib/test_hmm.c-400-\t\tif (ret)\n--\nmm/hmm.c=689=static int hmm_range_fault_locked(struct hmm_range *range, bool *locked)\n--\nmm/hmm.c-753- * The mmap lock must be held by the caller and will remain held on return.\nmm/hmm.c:754: * New users should prefer hmm_range_fault_unlocked_timeout() unless they\nmm/hmm.c-755- * specifically need to keep the mmap lock held across the call. This helper\n--\nmm/hmm.c=762=EXPORT_SYMBOL(hmm_range_fault);\n--\nmm/hmm.c-764-/**\nmm/hmm.c:765: * hmm_range_fault_unlocked_timeout - fault in a range with a retry timeout\nmm/hmm.c-766- * @range:\targument structure\n--\nmm/hmm.c-783- */\nmm/hmm.c:784:int hmm_range_fault_unlocked_timeout(struct hmm_range *range,\nmm/hmm.c-785-\t\t\t\t     unsigned long timeout)\n--\nmm/hmm.c-824-}\nmm/hmm.c:825:EXPORT_SYMBOL(hmm_range_fault_unlocked_timeout);\nmm/hmm.c-826-\n--\ntools/testing/selftests/mm/hmm-tests.c=2904=TEST_F_TIMEOUT(hmm, benchmark_thp_migration, 120)\n--\ntools/testing/selftests/mm/hmm-tests.c-2960- * Test that HMM can fault in pages backed by userfaultfd using the\ntools/testing/selftests/mm/hmm-tests.c:2961: * hmm_range_fault_unlocked_timeout() path with no timeout. This exercises\ntools/testing/selftests/mm/hmm-tests.c-2962- * the lock-drop retry logic in the HMM framework.\n"
}

gemini-3.1-pro-preview

null

null

							input: 7335
							output: 25
							thoughts: 477
						

**Analyzing the Timeout Parameter in `hmm_range_fault_unlocked_timeout`**

Okay, so I'm looking at this patch and immediately, the change to how the `timeout` parameter is handled in `hmm_range_fault_unlocked_timeout` catches my eye. It appears the signature of the function is being treated as taking an `unsigned long timeout` parameter. I need to understand this new approach.

Looking at the code diffs, specifically in `aie2_ctx.c`, `drm_gpusvm.c`, and `nouveau_svm.c`, it seems that the code used to calculate an *absolute* timeout, often by adding `jiffies` to a duration. In essence, they were setting an *expiration time*. Now, the patch is removing the `jiffies` addition and directly passing a timeout value calculated using `msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT)`. Also, the calls were previously subtracting `jiffies` from the timeout and using `max()` to ensure the timeout was at least 1, but now those calculations are removed.

This immediately suggests that `hmm_range_fault_unlocked_timeout` now expects a *relative* timeout – a duration, not an absolute timestamp. It's expecting the number of jiffies to wait. I *need* to confirm this. To be absolutely sure, I'm going to jump to the implementation of `hmm_range_fault_unlocked_timeout` in `mm/hmm.c` to verify whether it interprets the `timeout` parameter as a relative time value. If the code is now passing an absolute time, the patch is wrong and will break.

{
  "Expression": "int hmm_range_fault_unlocked_timeout"
}

{
  "Output": "Documentation/mm/hmm.rst=160=normal interface is::\nDocumentation/mm/hmm.rst-161-\nDocumentation/mm/hmm.rst:162:  int hmm_range_fault_unlocked_timeout(struct hmm_range *range,\nDocumentation/mm/hmm.rst-163-                                       unsigned long timeout);\n--\ninclude/linux/hmm.h=125=int hmm_range_fault(struct hmm_range *range);\ninclude/linux/hmm.h:126:int hmm_range_fault_unlocked_timeout(struct hmm_range *range,\ninclude/linux/hmm.h-127-\t\t\t\t     unsigned long timeout);\n--\nmm/hmm.c=762=EXPORT_SYMBOL(hmm_range_fault);\n--\nmm/hmm.c-783- */\nmm/hmm.c:784:int hmm_range_fault_unlocked_timeout(struct hmm_range *range,\nmm/hmm.c-785-\t\t\t\t     unsigned long timeout)\n"
}

gemini-3.1-pro-preview

null

null

							input: 8460
							output: 33
							thoughts: 24
						

Here's my summary, as though I'm reading and thinking about the code:

**Diving into `hmm_range_fault_unlocked_timeout`**

Okay, time to dive into `mm/hmm.c` and specifically, that function, `hmm_range_fault_unlocked_timeout`. The name itself is intriguing.  It suggests handling a fault within a Hyper-Memory Management (HMM) range, but we're dealing with a situation where some kind of lock is *not* held, and we're also dealing with a timeout.  This likely indicates a background process, or maybe asynchronous operation, and we’re trying to prevent it from blocking indefinitely. My experience tells me that these timeout scenarios often point to concurrency issues or resource contention, so I'll be looking for how that's addressed.

I'll be paying close attention to the conditions under which this function gets called. Is it triggered by a timer, an interrupt, or something else? Understanding the calling context is key to understanding the problem it's designed to solve.

I’ll also keep an eye out for how it interacts with other HMM components, such as range metadata, page tables, and any potential locking mechanisms (even if not explicitly held by the caller). Given that it's "unlocked," the function probably relies on some other mechanism to ensure data consistency. Maybe atomic operations? Perhaps read-copy-update techniques? I'll be looking for clues. The "timeout" aspect makes me think about potential deadlocks or livelocks – I'll be looking at whether it takes steps to mitigate those possibilities.

{
  "File": "mm/hmm.c",
  "FirstLine": 780,
  "LineCount": 50
}

{
  "Contents": " 780:\t * Returns 0 on success or one of the error codes documented for\n 781:\t * hmm_range_fault(). -EINTR is returned if mmap_lock acquisition is\n 782:\t * interrupted or a fatal signal is pending during retry handling.\n 783:\t */\n 784:\tint hmm_range_fault_unlocked_timeout(struct hmm_range *range,\n 785:\t\t\t\t\t     unsigned long timeout)\n 786:\t{\n 787:\t\tstruct mm_struct *mm = range-\u003enotifier-\u003emm;\n 788:\t\tunsigned long deadline = 0;\n 789:\t\tbool locked = false;\n 790:\t\tint ret;\n 791:\t\n 792:\t\tdo {\n 793:\t\t\tif (fatal_signal_pending(current))\n 794:\t\t\t\treturn -EINTR;\n 795:\t\n 796:\t\t\tif (timeout) {\n 797:\t\t\t\t/*\n 798:\t\t\t\t * If the previous fault dropped mmap_lock, then the fault\n 799:\t\t\t\t * handler made progress. Restart the retry timeout in that\n 800:\t\t\t\t * case, but keep the existing deadline for ordinary -EBUSY\n 801:\t\t\t\t * retries.\n 802:\t\t\t\t */\n 803:\t\t\t\tif (!locked)\n 804:\t\t\t\t\tdeadline = jiffies + timeout;\n 805:\t\n 806:\t\t\t\tif (time_after(jiffies, deadline))\n 807:\t\t\t\t\treturn -EBUSY;\n 808:\t\t\t}\n 809:\t\n 810:\t\t\trange-\u003enotifier_seq =\n 811:\t\t\t\tmmu_interval_read_begin(range-\u003enotifier);\n 812:\t\n 813:\t\t\tret = mmap_read_lock_killable(mm);\n 814:\t\t\tif (ret)\n 815:\t\t\t\treturn ret;\n 816:\t\n 817:\t\t\tlocked = true;\n 818:\t\t\tret = hmm_range_fault_locked(range, \u0026locked);\n 819:\t\t\tif (locked)\n 820:\t\t\t\tmmap_read_unlock(mm);\n 821:\t\t} while (ret == -EBUSY);\n 822:\t\n 823:\t\treturn ret;\n 824:\t}\n 825:\tEXPORT_SYMBOL(hmm_range_fault_unlocked_timeout);\n 826:\t\n 827:\t/**\n 828:\t * hmm_dma_map_alloc - Allocate HMM map structure\n 829:\t * @dev: device to allocate structure for\n"
}

gemini-3.1-pro-preview

null

null

							input: 9545
							output: 43
							thoughts: 338
						

**Analyzing the Timeout Logic in `hmm_range_fault_unlocked_timeout`**

Okay, so looking at `hmm_range_fault_unlocked_timeout`, it expects `timeout` to be a *relative* timeout, like the result of `msecs_to_jiffies(100)`. Inside, it adds this relative timeout to the current `jiffies` to get the deadline, but only if the memory region isn't locked. The code uses `deadline = jiffies + timeout;` when the region is unlocked, and then I realized that if the caller passes something like `max_t(long, timeout - jiffies, 1)`, where `timeout` was originally an *absolute* jiffies value, then it was effectively calculating the remaining time and passing it.

But hold on, `hmm_range_fault_unlocked_timeout` *itself* already handles the retry logic and restarts the timeout if the region isn't locked, which means progress was made. So the caller shouldn't be giving it the remaining time! It should be passing the *original* relative timeout, so that `hmm_range_fault_unlocked_timeout` can properly restart the timeout from scratch. It's supposed to manage the retries internally.

Now, a quick check of the nouveau driver reveals something interesting. It's still passing a `remaining` value. I see this:

```c
-		ret = hmm_range_fault_unlocked_timeout(&range,
-						       max(timeout - jiffies,
-							   1L));
+		ret = hmm_range_fault_unlocked_timeout(&range, remaining);
```

Wait, it looks like `nouveau_svm.c` already has its own loop around the `hmm_range_fault_unlocked_timeout` function? I need to dig into the `nouveau_svm.c` code to see what's going on there.

{
  "File": "drivers/gpu/drm/nouveau/nouveau_svm.c",
  "FirstLine": 670,
  "LineCount": 50
}

{
  "Contents": " 670:\t\n 671:\t\tret = mmu_interval_notifier_insert(\u0026notifier-\u003enotifier, mm,\n 672:\t\t\t\t\t\targs-\u003ep.addr, args-\u003ep.size,\n 673:\t\t\t\t\t\t\u0026nouveau_svm_mni_ops);\n 674:\t\tif (ret)\n 675:\t\t\treturn ret;\n 676:\t\n 677:\t\trange.start = notifier-\u003enotifier.interval_tree.start;\n 678:\t\trange.end = notifier-\u003enotifier.interval_tree.last + 1;\n 679:\t\n 680:\t\twhile (true) {\n 681:\t\t\tlong remaining = timeout - jiffies;\n 682:\t\n 683:\t\t\t/*\n 684:\t\t\t * The HMM timeout only bounds retries while HMM is walking and\n 685:\t\t\t * faulting the range. This fault is handled by a kernel worker,\n 686:\t\t\t * so fatal signals from the faulting process cannot stop an\n 687:\t\t\t * endless stream of invalidations here.\n 688:\t\t\t */\n 689:\t\t\tif (time_after_eq(jiffies, timeout)) {\n 690:\t\t\t\tret = -EBUSY;\n 691:\t\t\t\tgoto out;\n 692:\t\t\t}\n 693:\t\n 694:\t\t\tret = hmm_range_fault_unlocked_timeout(\u0026range, remaining);\n 695:\t\t\tif (ret)\n 696:\t\t\t\tgoto out;\n 697:\t\n 698:\t\t\tmutex_lock(\u0026svmm-\u003emutex);\n 699:\t\t\tif (mmu_interval_read_retry(range.notifier,\n 700:\t\t\t\t\t\t    range.notifier_seq)) {\n 701:\t\t\t\tmutex_unlock(\u0026svmm-\u003emutex);\n 702:\t\t\t\tcontinue;\n 703:\t\t\t}\n 704:\t\t\tbreak;\n 705:\t\t}\n 706:\t\n 707:\t\tnouveau_hmm_convert_pfn(drm, \u0026range, args);\n 708:\t\n 709:\t\tret = nvif_object_ioctl(\u0026svmm-\u003evmm-\u003evmm.object, args, size, NULL);\n 710:\t\tmutex_unlock(\u0026svmm-\u003emutex);\n 711:\t\n 712:\tout:\n 713:\t\tmmu_interval_notifier_remove(\u0026notifier-\u003enotifier);\n 714:\t\n 715:\t\treturn ret;\n 716:\t}\n 717:\t\n 718:\tstatic void\n 719:\tnouveau_svm_fault(struct work_struct *work)\n"
}

gemini-3.1-pro-preview

null

null

							input: 11042
							output: 23
							thoughts: 551
						

**Analyzing the Timeout Change in HMM Fault Handling**

Okay, so looking at this patch, I see it's touching `nouveau_svm.c`, and that's interesting because it has its own loop due to the `mmu_interval_read_retry` call. The core of the change seems to be around how the timeout is handled, specifically with `hmm_range_fault_unlocked_timeout`. The patch modifies `max(timeout - jiffies, 1L)` to `remaining`. This seems to be the fix.

It's clear the change affects how `timeout` is passed to `hmm_range_fault_unlocked_timeout`. Looking at `aie2_ctx.c` and `drm_gpusvm.c`, I see that the code is changing from using `max_t(long, timeout - jiffies, 1)` to just passing `timeout` directly (which is now a *relative* timeout). Wait, this is key! If `timeout` is relative now, `hmm_range_fault_unlocked_timeout` will restart the timeout if `!locked`.

Previously, the caller was passing `max_t(long, timeout - jiffies, 1)`, which represented the remaining time. Consequently, `hmm_range_fault_unlocked_timeout` was essentially restarting the timeout with the remaining time, making it functionally equivalent to *not* restarting the timeout at all, since `jiffies + (timeout - jiffies)` is just `timeout`.

Now, since the caller passes the relative timeout (like `msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT)`), `hmm_range_fault_unlocked_timeout` will restart the timeout with the *full* relative timeout. This means the timeout is extended every time the fault handler makes progress. That's a definite functional change.

Given this is a functional change, let me think about how it's used. Let's see if this code is reachable in virtualized environments. `aie2_ctx.c` is for the AMD XDNA driver (`drivers/accel/amdxdna`). `drm_gpusvm.c` is for DRM GPU SVM (`drivers/gpu/drm/drm_gpusvm.c`), and `nouveau_svm.c` is for Nouveau SVM (`drivers/gpu/drm/nouveau/nouveau_svm.c`). This leads me to want to see if `drm_gpusvm.c` is fuzzable. I need to investigate `drivers/gpu/drm/drm_gpusvm.c`.

{
  "Expression": "drm_gpusvm_scan_mm"
}

{
  "Output": "drivers/gpu/drm/drm_gpusvm.c=770=static bool drm_gpusvm_check_pages(struct drm_gpusvm *gpusvm,\n--\ndrivers/gpu/drm/drm_gpusvm.c-825-/**\ndrivers/gpu/drm/drm_gpusvm.c:826: * drm_gpusvm_scan_mm() - Check the migration state of a drm_gpusvm_range\ndrivers/gpu/drm/drm_gpusvm.c-827- * @range: Pointer to the struct drm_gpusvm_range to check.\n--\ndrivers/gpu/drm/drm_gpusvm.c-840- */\ndrivers/gpu/drm/drm_gpusvm.c:841:enum drm_gpusvm_scan_result drm_gpusvm_scan_mm(struct drm_gpusvm_range *range,\ndrivers/gpu/drm/drm_gpusvm.c-842-\t\t\t\t\t       void *dev_private_owner,\n--\ndrivers/gpu/drm/drm_gpusvm.c-927-}\ndrivers/gpu/drm/drm_gpusvm.c:928:EXPORT_SYMBOL(drm_gpusvm_scan_mm);\ndrivers/gpu/drm/drm_gpusvm.c-929-\n--\ndrivers/gpu/drm/xe/xe_svm.c=1648=int xe_svm_alloc_vram(struct xe_svm_range *range, const struct drm_gpusvm_ctx *ctx,\n--\ndrivers/gpu/drm/xe/xe_svm.c-1664-\ndrivers/gpu/drm/xe/xe_svm.c:1665:\tmigration_state = drm_gpusvm_scan_mm(\u0026range-\u003ebase,\ndrivers/gpu/drm/xe/xe_svm.c-1666-\t\t\t\t\t     xe_svm_private_page_owner(vm, false),\n--\ninclude/drm/drm_gpusvm.h=350=static inline void drm_gpusvm_init_pages(struct drm_gpusvm_pages *svm_pages,\n--\ninclude/drm/drm_gpusvm.h-358-/**\ninclude/drm/drm_gpusvm.h:359: * enum drm_gpusvm_scan_result - Scan result from the drm_gpusvm_scan_mm() function.\ninclude/drm/drm_gpusvm.h-360- * @DRM_GPUSVM_SCAN_UNPOPULATED: At least one page was not present or inaccessible.\ninclude/drm/drm_gpusvm.h-361- * @DRM_GPUSVM_SCAN_EQUAL: All pages belong to the struct dev_pagemap indicated as\ninclude/drm/drm_gpusvm.h:362: * the @pagemap argument to the drm_gpusvm_scan_mm() function.\ninclude/drm/drm_gpusvm.h-363- * @DRM_GPUSVM_SCAN_OTHER: All pages belong to exactly one dev_pagemap, which is\ninclude/drm/drm_gpusvm.h:364: * *NOT* the @pagemap argument to the drm_gpusvm_scan_mm(). All pages belong to\ninclude/drm/drm_gpusvm.h-365- * the same device private owner.\n--\ninclude/drm/drm_gpusvm.h=374=enum drm_gpusvm_scan_result {\n--\ninclude/drm/drm_gpusvm.h-382-\ninclude/drm/drm_gpusvm.h:383:enum drm_gpusvm_scan_result drm_gpusvm_scan_mm(struct drm_gpusvm_range *range,\ninclude/drm/drm_gpusvm.h-384-\t\t\t\t\t       void *dev_private_owner,\n"
}

gemini-3.1-pro-preview

null

null

							input: 13129
							output: 23
							thoughts: 132
						

**Analyzing GPU Virtualization and Driver Interactions**

Okay, so `drm_gpusvm_scan_mm` is being called by `xe_svm_alloc_vram` within the `xe` driver, specifically in `drivers/gpu/drm/xe/xe_svm.c`. The question immediately popping into my head is, can the `xe` driver, Intel's Xe graphics driver, even be triggered within a virtualized environment? It's hardware-specific, requiring actual Intel Xe silicon, but perhaps there's a fuzzing avenue through something like VGEM or VKMS? No, that's not quite right; `xe` is a *hardware* driver through and through.

Then my mind shifted to consider `nouveau_svm.c`. Now, *that* would be interesting. The NVIDIA driver, `nouveau`, and the general concept of GPU virtualization... how might that play out? Any relevant interactions with `drm_gpusvm_get_pages` that could provide a different entry point into the overall flow? I should dig into that.

{
  "Expression": "drm_gpusvm_get_pages"
}

{
  "Output": "Documentation/gpu/rfc/gpusvm.rst=91=Possible future design features\n--\nDocumentation/gpu/rfc/gpusvm.rst-100-* Ranges with mixed system and device pages\nDocumentation/gpu/rfc/gpusvm.rst:101:\t* Can be added if required to drm_gpusvm_get_pages fairly easily.\nDocumentation/gpu/rfc/gpusvm.rst-102-* Multi-GPU support\n--\ndrivers/gpu/drm/drm_gpusvm.c-234- *\ndrivers/gpu/drm/drm_gpusvm.c:235: *\t\terr = drm_gpusvm_get_pages(gpusvm, \u0026drange-\u003epages,\ndrivers/gpu/drm/drm_gpusvm.c-236- *\t\t\t\t\t   gpusvm-\u003emm, \u0026range-\u003enotifier-\u003enotifier,\n--\ndrivers/gpu/drm/drm_gpusvm.c=434=static const struct mmu_interval_notifier_ops drm_gpusvm_notifier_ops = {\n--\ndrivers/gpu/drm/drm_gpusvm.c-456- * mappings is bound per-pages via drm_gpusvm_init_pages() before the first\ndrivers/gpu/drm/drm_gpusvm.c:457: * drm_gpusvm_get_pages() call. However, the same base\ndrivers/gpu/drm/drm_gpusvm.c-458- * @gpusvm can also be used with both modes together in which case the full\n--\ndrivers/gpu/drm/drm_gpusvm.c=948=drm_gpusvm_range_chunk_size(struct drm_gpusvm *gpusvm,\n--\ndrivers/gpu/drm/drm_gpusvm.c-994-\t\t * drm_pagemap_migrate_to_devmem with 'migrate.cpages != npages'\ndrivers/gpu/drm/drm_gpusvm.c:995:\t\t * and then upon drm_gpusvm_get_pages device pages from\ndrivers/gpu/drm/drm_gpusvm.c-996-\t\t * other processes are collected + faulted in which creates all\n--\ndrivers/gpu/drm/drm_gpusvm.c=1412=static bool drm_gpusvm_pages_valid_unlocked(struct drm_gpusvm *gpusvm,\n--\ndrivers/gpu/drm/drm_gpusvm.c-1429-/**\ndrivers/gpu/drm/drm_gpusvm.c:1430: * drm_gpusvm_get_pages() - Get pages and populate GPU SVM pages struct\ndrivers/gpu/drm/drm_gpusvm.c-1431- * @gpusvm: Pointer to the GPU SVM structure\n--\ndrivers/gpu/drm/drm_gpusvm.c-1443- */\ndrivers/gpu/drm/drm_gpusvm.c:1444:int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,\ndrivers/gpu/drm/drm_gpusvm.c-1445-\t\t\t struct drm_gpusvm_pages *svm_pages,\n--\ndrivers/gpu/drm/drm_gpusvm.c-1661-}\ndrivers/gpu/drm/drm_gpusvm.c:1662:EXPORT_SYMBOL_GPL(drm_gpusvm_get_pages);\ndrivers/gpu/drm/drm_gpusvm.c-1663-\n--\ndrivers/gpu/drm/xe/xe_svm.c=1533=int xe_svm_range_get_pages(struct xe_vm *vm, struct xe_svm_range *range,\n--\ndrivers/gpu/drm/xe/xe_svm.c-1537-\ndrivers/gpu/drm/xe/xe_svm.c:1538:\terr = drm_gpusvm_get_pages(\u0026vm-\u003esvm.gpusvm, \u0026range-\u003epages,\ndrivers/gpu/drm/xe/xe_svm.c-1539-\t\t\t\t   vm-\u003esvm.gpusvm.mm,\n--\ndrivers/gpu/drm/xe/xe_userptr.c=60=int xe_vma_userptr_pin_pages(struct xe_userptr_vma *uvma)\n--\ndrivers/gpu/drm/xe/xe_userptr.c-76-\ndrivers/gpu/drm/xe/xe_userptr.c:77:\treturn drm_gpusvm_get_pages(\u0026vm-\u003esvm.gpusvm, \u0026uvma-\u003euserptr.pages,\ndrivers/gpu/drm/xe/xe_userptr.c-78-\t\t\t\t    uvma-\u003euserptr.notifier.mm,\n--\ninclude/drm/drm_gpusvm.h=320=void drm_gpusvm_range_set_unmapped(struct drm_gpusvm_range *range,\n--\ninclude/drm/drm_gpusvm.h-324-\ninclude/drm/drm_gpusvm.h:325:int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,\ninclude/drm/drm_gpusvm.h-326-\t\t\t struct drm_gpusvm_pages *svm_pages,\n--\ninclude/drm/drm_gpusvm.h=337=void drm_gpusvm_free_pages(struct drm_gpusvm *gpusvm,\n--\ninclude/drm/drm_gpusvm.h-347- * structure must call this once on each pages instance after allocation,\ninclude/drm/drm_gpusvm.h:348: * before the first drm_gpusvm_get_pages() / unmap / free.\ninclude/drm/drm_gpusvm.h-349- */\n"
}

gemini-3.1-pro-preview

null

null

							input: 14919
							output: 24
							thoughts: 295
						

**My Initial Assessment of DRM GPU SVM Usage in Syzkaller Fuzzing**

Okay, so I'm looking at `drm_gpusvm_get_pages`. It's used by the `xe` driver, specifically within `xe_svm_range_get_pages` and `xe_vma_userptr_pin_pages`. Right, `drm_gpusvm` is a generic helper function, essentially a DRM-level abstraction for GPU Shared Virtual Memory. It seems like the `xe` driver is currently the primary user. Hold on a second, what about the other drivers?

I need to quickly check the landscape. `nouveau_svm.c` implements SVM functionality for the `nouveau` driver. And I also see a similar file for the amdxdna driver `aie2_ctx.c`.

Now the question is, are any of these drivers reachable by syzkaller? `nouveau` is a tricky one. Syzkaller *can* fuzz it if you're using a virtual GPU or some kind of mocking setup, but it typically needs real hardware to really test the functionality. That's a huge hurdle to overcome.

Thinking about other drivers, I see how they've managed to achieve some level of syzkaller coverage, with the likes of `syz-usb` and `vhci` for USB devices, `mac80211_hwsim` for wifi. And within DRM, syzkaller leverages `vkms` and `vgem` as a virtual device.

But `xe`, `nouveau`, and `amdxdna` are hardware-specific drivers. That's a tough constraint. I need to figure out what functionality is easily accessible.

Oh, and here's a thought, `hmm_range_fault_unlocked_timeout` is a core mm/hmm function. Is it used by any other drivers besides the ones I've already considered? That could provide a more generalized entry point for fuzzing. That's the key: a more generic access point.

{
  "Expression": "hmm_range_fault_unlocked_timeout"
}

{
  "Output": "Documentation/mm/hmm.rst=160=normal interface is::\nDocumentation/mm/hmm.rst-161-\nDocumentation/mm/hmm.rst:162:  int hmm_range_fault_unlocked_timeout(struct hmm_range *range,\nDocumentation/mm/hmm.rst-163-                                       unsigned long timeout);\n--\nDocumentation/mm/hmm.rst=169=The caller must not hold ``mmap_read_lock`` before the call.\nDocumentation/mm/hmm.rst:170:``hmm_range_fault_unlocked_timeout()`` takes the mmap read lock internally and\nDocumentation/mm/hmm.rst-171-allows ``handle_mm_fault()`` to drop it during fault handling. This is required\n--\nDocumentation/mm/hmm.rst=186=The usage pattern is::\n--\nDocumentation/mm/hmm.rst-203- again:\nDocumentation/mm/hmm.rst:204:      ret = hmm_range_fault_unlocked_timeout(\u0026range, timeout);\nDocumentation/mm/hmm.rst-205-      if (ret)\n--\nDocumentation/mm/hmm.rst=228=update. The retry check must use the same notifier and sequence number stored\nDocumentation/mm/hmm.rst:229:in ``range`` by ``hmm_range_fault_unlocked_timeout()``.\nDocumentation/mm/hmm.rst-230-\nDocumentation/mm/hmm.rst=231=Holding the mmap lock across HMM faults\n--\nDocumentation/mm/hmm.rst-233-\nDocumentation/mm/hmm.rst:234:Most callers should use ``hmm_range_fault_unlocked_timeout()``. If a driver\nDocumentation/mm/hmm.rst-235-really needs to hold the mmap lock across work outside HMM, it can use::\n--\nDocumentation/mm/hmm.rst=240=interface cannot support VMAs whose fault handlers need to drop the mmap lock.\nDocumentation/mm/hmm.rst:241:New callers should prefer ``hmm_range_fault_unlocked_timeout()`` unless they\nDocumentation/mm/hmm.rst-242-have a specific requirement to keep the mmap lock held across the call.\n--\ndrivers/accel/amdxdna/aie2_ctx.c=1031=static int aie2_populate_range(struct amdxdna_gem_obj *abo)\n--\ndrivers/accel/amdxdna/aie2_ctx.c-1064-\ndrivers/accel/amdxdna/aie2_ctx.c:1065:\tret = hmm_range_fault_unlocked_timeout(\u0026mapp-\u003erange, timeout);\ndrivers/accel/amdxdna/aie2_ctx.c-1066-\tif (ret)\n--\ndrivers/gpu/drm/drm_gpusvm.c=841=enum drm_gpusvm_scan_result drm_gpusvm_scan_mm(struct drm_gpusvm_range *range,\n--\ndrivers/gpu/drm/drm_gpusvm.c-868-retry:\ndrivers/gpu/drm/drm_gpusvm.c:869:\terr = hmm_range_fault_unlocked_timeout(\u0026hmm_range, timeout);\ndrivers/gpu/drm/drm_gpusvm.c-870-\tif (err)\n--\ndrivers/gpu/drm/drm_gpusvm.c=1444=int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,\n--\ndrivers/gpu/drm/drm_gpusvm.c-1491-\thmm_range.hmm_pfns = pfns;\ndrivers/gpu/drm/drm_gpusvm.c:1492:\terr = hmm_range_fault_unlocked_timeout(\u0026hmm_range, timeout);\ndrivers/gpu/drm/drm_gpusvm.c-1493-\tmmput(mm);\n--\ndrivers/gpu/drm/drm_gpusvm.c=1703=int drm_gpusvm_range_evict(struct drm_gpusvm *gpusvm,\n--\ndrivers/gpu/drm/drm_gpusvm.c-1728-\thmm_range.hmm_pfns = pfns;\ndrivers/gpu/drm/drm_gpusvm.c:1729:\terr = hmm_range_fault_unlocked_timeout(\u0026hmm_range, timeout);\ndrivers/gpu/drm/drm_gpusvm.c-1730-\n--\ndrivers/gpu/drm/nouveau/nouveau_svm.c=652=static int nouveau_range_fault(struct nouveau_svmm *svmm,\n--\ndrivers/gpu/drm/nouveau/nouveau_svm.c-693-\ndrivers/gpu/drm/nouveau/nouveau_svm.c:694:\t\tret = hmm_range_fault_unlocked_timeout(\u0026range, remaining);\ndrivers/gpu/drm/nouveau/nouveau_svm.c-695-\t\tif (ret)\n--\ndrivers/hv/mshv_regions.c=396=static int mshv_region_range_fault(struct mshv_mem_region *region,\n--\ndrivers/hv/mshv_regions.c-415-again:\ndrivers/hv/mshv_regions.c:416:\tret = hmm_range_fault_unlocked_timeout(\u0026range, 0);\ndrivers/hv/mshv_regions.c-417-\tif (ret)\n--\ndrivers/infiniband/core/umem_odp.c=324=int ib_umem_odp_map_dma_and_lock(struct ib_umem_odp *umem_odp, u64 user_virt,\n--\ndrivers/infiniband/core/umem_odp.c-368-retry:\ndrivers/infiniband/core/umem_odp.c:369:\tret = hmm_range_fault_unlocked_timeout(\u0026range, timeout);\ndrivers/infiniband/core/umem_odp.c-370-\tif (unlikely(ret))\n--\ninclude/linux/hmm.h=125=int hmm_range_fault(struct hmm_range *range);\ninclude/linux/hmm.h:126:int hmm_range_fault_unlocked_timeout(struct hmm_range *range,\ninclude/linux/hmm.h-127-\t\t\t\t     unsigned long timeout);\n--\nlib/test_hmm.c=392=static int dmirror_range_fault_unlocked(struct dmirror *dmirror,\n--\nlib/test_hmm.c-398-\twhile (true) {\nlib/test_hmm.c:399:\t\tret = hmm_range_fault_unlocked_timeout(range, timeout);\nlib/test_hmm.c-400-\t\tif (ret)\n--\nmm/hmm.c=689=static int hmm_range_fault_locked(struct hmm_range *range, bool *locked)\n--\nmm/hmm.c-753- * The mmap lock must be held by the caller and will remain held on return.\nmm/hmm.c:754: * New users should prefer hmm_range_fault_unlocked_timeout() unless they\nmm/hmm.c-755- * specifically need to keep the mmap lock held across the call. This helper\n--\nmm/hmm.c=762=EXPORT_SYMBOL(hmm_range_fault);\n--\nmm/hmm.c-764-/**\nmm/hmm.c:765: * hmm_range_fault_unlocked_timeout - fault in a range with a retry timeout\nmm/hmm.c-766- * @range:\targument structure\n--\nmm/hmm.c-783- */\nmm/hmm.c:784:int hmm_range_fault_unlocked_timeout(struct hmm_range *range,\nmm/hmm.c-785-\t\t\t\t     unsigned long timeout)\n--\nmm/hmm.c-824-}\nmm/hmm.c:825:EXPORT_SYMBOL(hmm_range_fault_unlocked_timeout);\nmm/hmm.c-826-\n--\ntools/testing/selftests/mm/hmm-tests.c=2904=TEST_F_TIMEOUT(hmm, benchmark_thp_migration, 120)\n--\ntools/testing/selftests/mm/hmm-tests.c-2960- * Test that HMM can fault in pages backed by userfaultfd using the\ntools/testing/selftests/mm/hmm-tests.c:2961: * hmm_range_fault_unlocked_timeout() path with no timeout. This exercises\ntools/testing/selftests/mm/hmm-tests.c-2962- * the lock-drop retry logic in the HMM framework.\n"
}

gemini-3.1-pro-preview

null

null

							input: 17853
							output: 35
							thoughts: 83
						

Okay, let me delve into this.

**Investigating a Timeout in the HMM System**

Alright, so `lib/test_hmm.c` is using `hmm_range_fault_unlocked_timeout`. Hmm, that's interesting. I need to figure out why this is relevant to the patch in question. The initial assumption would be a direct connection, but wait, the patch *didn't* touch either `lib/test_hmm.c` or `drivers/infiniband/core/umem_odp.c`. That means the connection isn't as obvious as I initially thought. I need to understand how the timeout parameter is being passed within `lib/test_hmm.c`. So, I'll need to dig into that specific test file to see how it's actually using the `timeout` variable passed to the function, and hopefully, that will shed some light on the issue.

{
  "File": "lib/test_hmm.c",
  "FirstLine": 380,
  "LineCount": 50
}

{
  "Contents": " 380:\t\t\t\tcontinue;\n 381:\t\t\t}\n 382:\t\t\tbreak;\n 383:\t\t}\n 384:\t\n 385:\t\tret = dmirror_do_fault(dmirror, range);\n 386:\t\n 387:\t\tmutex_unlock(\u0026dmirror-\u003emutex);\n 388:\tout:\n 389:\t\treturn ret;\n 390:\t}\n 391:\t\n 392:\tstatic int dmirror_range_fault_unlocked(struct dmirror *dmirror,\n 393:\t\t\t\t\t\tstruct hmm_range *range,\n 394:\t\t\t\t\t\tunsigned long timeout)\n 395:\t{\n 396:\t\tint ret;\n 397:\t\n 398:\t\twhile (true) {\n 399:\t\t\tret = hmm_range_fault_unlocked_timeout(range, timeout);\n 400:\t\t\tif (ret)\n 401:\t\t\t\tgoto out;\n 402:\t\n 403:\t\t\tmutex_lock(\u0026dmirror-\u003emutex);\n 404:\t\t\tif (mmu_interval_read_retry(range-\u003enotifier,\n 405:\t\t\t\t\t\t    range-\u003enotifier_seq)) {\n 406:\t\t\t\tmutex_unlock(\u0026dmirror-\u003emutex);\n 407:\t\t\t\tcontinue;\n 408:\t\t\t}\n 409:\t\t\tbreak;\n 410:\t\t}\n 411:\t\n 412:\t\tret = dmirror_do_fault(dmirror, range);\n 413:\t\n 414:\t\tmutex_unlock(\u0026dmirror-\u003emutex);\n 415:\tout:\n 416:\t\treturn ret;\n 417:\t}\n 418:\t\n 419:\tstatic int dmirror_fault_unlocked(struct dmirror *dmirror,\n 420:\t\t\t\t\t  unsigned long start,\n 421:\t\t\t\t\t  unsigned long end, bool write,\n 422:\t\t\t\t\t  unsigned long timeout)\n 423:\t{\n 424:\t\tstruct mm_struct *mm = dmirror-\u003enotifier.mm;\n 425:\t\tunsigned long addr;\n 426:\t\tunsigned long pfns[32];\n 427:\t\tstruct hmm_range range = {\n 428:\t\t\t.notifier = \u0026dmirror-\u003enotifier,\n 429:\t\t\t.hmm_pfns = pfns,\n"
}

gemini-3.1-pro-preview

null

null

							input: 18792
							output: 35
							thoughts: 23
						

Here's my thought process, as requested:

**Investigating the `timeout` Variable in `lib/test_hmm.c`**

Okay, so I'm looking at `lib/test_hmm.c` and I immediately spot the `timeout` variable being passed directly, and that triggers a question. It seems pretty straightforward that `timeout` is passed right into some function call. But, the question now is, where the heck is this `timeout` variable being *defined*? I need to trace back its origin. Is it coming from the command line, an environment variable, a configuration file, or is it hardcoded somewhere upstream in the build process? I'm going to have to check the surrounding code, the build system (Makefile, CMakeLists.txt, whatever), and any relevant initialization routines to figure out where the value for `timeout` is being set. It's crucial for understanding the test's behavior and potential vulnerabilities if this value isn't properly controlled or sanitized. It's a classic example of looking for the source of a parameter.

{
  "File": "lib/test_hmm.c",
  "FirstLine": 419,
  "LineCount": 50
}

{
  "Contents": " 419:\tstatic int dmirror_fault_unlocked(struct dmirror *dmirror,\n 420:\t\t\t\t\t  unsigned long start,\n 421:\t\t\t\t\t  unsigned long end, bool write,\n 422:\t\t\t\t\t  unsigned long timeout)\n 423:\t{\n 424:\t\tstruct mm_struct *mm = dmirror-\u003enotifier.mm;\n 425:\t\tunsigned long addr;\n 426:\t\tunsigned long pfns[32];\n 427:\t\tstruct hmm_range range = {\n 428:\t\t\t.notifier = \u0026dmirror-\u003enotifier,\n 429:\t\t\t.hmm_pfns = pfns,\n 430:\t\t\t.pfn_flags_mask = 0,\n 431:\t\t\t.default_flags =\n 432:\t\t\t\tHMM_PFN_REQ_FAULT | (write ? HMM_PFN_REQ_WRITE : 0),\n 433:\t\t\t.dev_private_owner = dmirror-\u003emdevice,\n 434:\t\t};\n 435:\t\tint ret = 0;\n 436:\t\n 437:\t\tif (!mmget_not_zero(mm))\n 438:\t\t\treturn -EFAULT;\n 439:\t\n 440:\t\tfor (addr = start; addr \u003c end; addr = range.end) {\n 441:\t\t\trange.start = addr;\n 442:\t\t\trange.end = min(addr + (ARRAY_SIZE(pfns) \u003c\u003c PAGE_SHIFT), end);\n 443:\t\n 444:\t\t\tret = dmirror_range_fault_unlocked(dmirror, \u0026range, timeout);\n 445:\t\t\tif (ret)\n 446:\t\t\t\tbreak;\n 447:\t\t}\n 448:\t\n 449:\t\tmmput(mm);\n 450:\t\treturn ret;\n 451:\t}\n 452:\t\n 453:\tstatic int dmirror_fault(struct dmirror *dmirror, unsigned long start,\n 454:\t\t\t\t unsigned long end, bool write)\n 455:\t{\n 456:\t\tstruct mm_struct *mm = dmirror-\u003enotifier.mm;\n 457:\t\tunsigned long addr;\n 458:\t\tunsigned long pfns[32];\n 459:\t\tstruct hmm_range range = {\n 460:\t\t\t.notifier = \u0026dmirror-\u003enotifier,\n 461:\t\t\t.hmm_pfns = pfns,\n 462:\t\t\t.pfn_flags_mask = 0,\n 463:\t\t\t.default_flags =\n 464:\t\t\t\tHMM_PFN_REQ_FAULT | (write ? HMM_PFN_REQ_WRITE : 0),\n 465:\t\t\t.dev_private_owner = dmirror-\u003emdevice,\n 466:\t\t};\n 467:\t\tint ret = 0;\n 468:\t\n"
}

gemini-3.1-pro-preview

null

null

							input: 19824
							output: 21
							thoughts: 17
						

Here's my thought process, as if I were analyzing that code:

**Finding the Callers of `dmirror_fault_unlocked`**

Okay, so I need to understand the context of `dmirror_fault_unlocked`. It's named in a way that suggests it's related to some kind of data mirroring, perhaps a fault condition, and possibly working with an unlocked mutex. The "unlocked" part is important; it implies a critical section is *not* protected when this function is being used, so concurrency considerations become paramount. First, I need to pinpoint everywhere this function is actually called within the codebase. The sheer number of locations will give me a good indication of this function's overall significance to the software and will help me narrow down where it's most important to analyze. Once I know the calling points, I can start looking at the immediate surrounding code to understand the specific operations happening around that fault handling.

{
  "Expression": "dmirror_fault_unlocked"
}

{
  "Output": "lib/test_hmm.c=392=static int dmirror_range_fault_unlocked(struct dmirror *dmirror,\n--\nlib/test_hmm.c-418-\nlib/test_hmm.c:419:static int dmirror_fault_unlocked(struct dmirror *dmirror,\nlib/test_hmm.c-420-\t\t\t\t  unsigned long start,\n--\nlib/test_hmm.c=552=static int dmirror_read_unlocked(struct dmirror *dmirror,\n--\nlib/test_hmm.c-577-\t\tstart = cmd-\u003eaddr + (bounce.cpages \u003c\u003c PAGE_SHIFT);\nlib/test_hmm.c:578:\t\tret = dmirror_fault_unlocked(dmirror, start, end, false, timeout);\nlib/test_hmm.c-579-\t\tif (ret)\n"
}

gemini-3.1-pro-preview

null

null

							input: 20284
							output: 35
							thoughts: 23
						

Here's a summary of my thought process, as requested:

**Deconstructing the `test_hmm.c` Conundrum**

Okay, first things first, I need to get a handle on what's going on in `lib/test_hmm.c`. My immediate focus is on that `dmirror_read_unlocked` function call. I recognize that naming convention, so I'm thinking this likely involves some sort of direct memory access related to a mirror or duplicate data structure, and the "unlocked" part suggests we're bypassing typical concurrency controls. Knowing the project and the context is key here, I need to figure out the specifics. Is this a read-only access? What's the lock protecting? What’s the implication of bypassing the lock? Is it for performance optimization, or is there a reason this particular code section doesn't need the lock? I need to analyze the surrounding code to understand the context and the potential risks or benefits of using this unlocked read. My expertise should allow me to spot any red flags related to data corruption, race conditions, or unexpected behavior.

{
  "File": "lib/test_hmm.c",
  "FirstLine": 550,
  "LineCount": 50
}

{
  "Contents": " 550:\t}\n 551:\t\n 552:\tstatic int dmirror_read_unlocked(struct dmirror *dmirror,\n 553:\t\t\t\t\t struct hmm_dmirror_cmd *cmd,\n 554:\t\t\t\t\t unsigned long timeout)\n 555:\t{\n 556:\t\tstruct dmirror_bounce bounce;\n 557:\t\tunsigned long start, end;\n 558:\t\tunsigned long size = cmd-\u003enpages \u003c\u003c PAGE_SHIFT;\n 559:\t\tint ret;\n 560:\t\n 561:\t\tstart = cmd-\u003eaddr;\n 562:\t\tend = start + size;\n 563:\t\tif (end \u003c start)\n 564:\t\t\treturn -EINVAL;\n 565:\t\n 566:\t\tret = dmirror_bounce_init(\u0026bounce, start, size);\n 567:\t\tif (ret)\n 568:\t\t\treturn ret;\n 569:\t\n 570:\t\twhile (1) {\n 571:\t\t\tmutex_lock(\u0026dmirror-\u003emutex);\n 572:\t\t\tret = dmirror_do_read(dmirror, start, end, \u0026bounce);\n 573:\t\t\tmutex_unlock(\u0026dmirror-\u003emutex);\n 574:\t\t\tif (ret != -ENOENT)\n 575:\t\t\t\tbreak;\n 576:\t\n 577:\t\t\tstart = cmd-\u003eaddr + (bounce.cpages \u003c\u003c PAGE_SHIFT);\n 578:\t\t\tret = dmirror_fault_unlocked(dmirror, start, end, false, timeout);\n 579:\t\t\tif (ret)\n 580:\t\t\t\tbreak;\n 581:\t\t\tcmd-\u003efaults++;\n 582:\t\t}\n 583:\t\n 584:\t\tif (ret == 0) {\n 585:\t\t\tif (copy_to_user(u64_to_user_ptr(cmd-\u003eptr), bounce.ptr,\n 586:\t\t\t\t\t bounce.size))\n 587:\t\t\t\tret = -EFAULT;\n 588:\t\t}\n 589:\t\tcmd-\u003ecpages = bounce.cpages;\n 590:\t\tdmirror_bounce_fini(\u0026bounce);\n 591:\t\treturn ret;\n 592:\t}\n 593:\t\n 594:\tstatic int dmirror_do_write(struct dmirror *dmirror, unsigned long start,\n 595:\t\t\t\t    unsigned long end, struct dmirror_bounce *bounce)\n 596:\t{\n 597:\t\tunsigned long pfn;\n 598:\t\tvoid *ptr;\n 599:\t\n"
}

gemini-3.1-pro-preview

null

null

							input: 21256
							output: 21
							thoughts: 17
						

Here's my thought process, as if I were analyzing that prompt:

**Analyzing the Call Sites of `dmirror_read_unlocked`**

Okay, so the initial direction is clear: I need to figure out where the `dmirror_read_unlocked` function is being used. This isn't just about *finding* the calls, but understanding their context. I'm already thinking about what that function likely does based on its name. "Mirror," "read," and "unlocked" suggest this has to do with reading from a mirrored data structure, and the "unlocked" part tells me there's some sort of concurrency consideration. It's likely involved in a read operation where exclusive locks aren't necessary.

My next move is probably to use a static analysis tool or a good old-fashioned grep to quickly identify all the call sites. I can use the tool to find cross-references for this specific function. I need to be efficient here – a quick search to get a list, and then I'll start to dig deeper. I'm expecting some kind of output in the form of a list of lines of code.

Once I've got that list, I'll need to rapidly scan through each call site to assess the surrounding code. I'll need to be mindful of how the return value is used, what locks are held (or not held) around the call, and what kind of data the function is operating on. The goal is to build a mental model of how this function fits into the overall system. Understanding the data flow will be crucial.

{
  "Expression": "dmirror_read_unlocked"
}

{
  "Output": "lib/test_hmm.c=512=static int dmirror_read(struct dmirror *dmirror, struct hmm_dmirror_cmd *cmd)\n--\nlib/test_hmm.c-551-\nlib/test_hmm.c:552:static int dmirror_read_unlocked(struct dmirror *dmirror,\nlib/test_hmm.c-553-\t\t\t\t struct hmm_dmirror_cmd *cmd,\n--\nlib/test_hmm.c=1616=static long dmirror_fops_unlocked_ioctl(struct file *filp,\n--\nlib/test_hmm.c-1678-\tcase HMM_DMIRROR_READ_UNLOCKED:\nlib/test_hmm.c:1679:\t\tret = dmirror_read_unlocked(dmirror, \u0026cmd, 0);\nlib/test_hmm.c-1680-\t\tbreak;\n"
}

gemini-3.1-pro-preview

null

null

							input: 21862
							output: 36
							thoughts: 90
						

Okay, let me think this through...

**Analyzing the dmirror Kernel Module's Timeout Handling**

Right, so I'm looking at this `dmirror_read_unlocked` function, and it's being called from `dmirror_fops_unlocked_ioctl`. And hang on...the `timeout` parameter passed to `dmirror_read_unlocked` is set to zero in that call! That's a bit odd. If `timeout` is zero, then the `hmm_range_fault_unlocked_timeout` function won't actually be using any of its timeout logic, will it? It'll bypass that whole timeout mechanism entirely.

I need to confirm if this is the only case where `dmirror_read_unlocked` is called from `dmirror_fops_unlocked_ioctl`. I should really go back and check the other calls within `dmirror_fops_unlocked_ioctl` to make sure there aren't any other scenarios or possible issues that might arise. This needs a deeper dive.

{
  "File": "lib/test_hmm.c",
  "FirstLine": 1670,
  "LineCount": 50
}

{
  "Contents": "1670:\t\tcase HMM_DMIRROR_RELEASE:\n1671:\t\t\tdmirror_device_remove_chunks(dmirror-\u003emdevice);\n1672:\t\t\tret = 0;\n1673:\t\t\tbreak;\n1674:\t\tcase HMM_DMIRROR_FLAGS:\n1675:\t\t\tdmirror-\u003eflags = cmd.npages;\n1676:\t\t\tret = 0;\n1677:\t\t\tbreak;\n1678:\t\tcase HMM_DMIRROR_READ_UNLOCKED:\n1679:\t\t\tret = dmirror_read_unlocked(dmirror, \u0026cmd, 0);\n1680:\t\t\tbreak;\n1681:\t\tdefault:\n1682:\t\t\treturn -EINVAL;\n1683:\t\t}\n1684:\t\tif (ret)\n1685:\t\t\treturn ret;\n1686:\t\n1687:\t\tif (copy_to_user(uarg, \u0026cmd, sizeof(cmd)))\n1688:\t\t\treturn -EFAULT;\n1689:\t\n1690:\t\treturn 0;\n1691:\t}\n1692:\t\n1693:\tstatic int dmirror_fops_mmap(struct file *file, struct vm_area_struct *vma)\n1694:\t{\n1695:\t\tunsigned long addr;\n1696:\t\n1697:\t\tfor (addr = vma-\u003evm_start; addr \u003c vma-\u003evm_end; addr += PAGE_SIZE) {\n1698:\t\t\tstruct page *page;\n1699:\t\t\tint ret;\n1700:\t\n1701:\t\t\tpage = alloc_page(GFP_KERNEL | __GFP_ZERO);\n1702:\t\t\tif (!page)\n1703:\t\t\t\treturn -ENOMEM;\n1704:\t\n1705:\t\t\tret = vm_insert_page(vma, addr, page);\n1706:\t\t\tif (ret) {\n1707:\t\t\t\t__free_page(page);\n1708:\t\t\t\treturn ret;\n1709:\t\t\t}\n1710:\t\t\tput_page(page);\n1711:\t\t}\n1712:\t\n1713:\t\treturn 0;\n1714:\t}\n1715:\t\n1716:\tstatic const struct file_operations dmirror_fops = {\n1717:\t\t.open\t\t= dmirror_fops_open,\n1718:\t\t.release\t= dmirror_fops_release,\n1719:\t\t.mmap\t\t= dmirror_fops_mmap,\n"
}

gemini-3.1-pro-preview

null

null

							input: 22899
							output: 44
							thoughts: 67
						

**Analyzing the Timeout Mechanism**

Okay, so I see this `timeout = 0` and my immediate thought is, "Wait, zero for a timeout? That usually means 'no timeout' in programming. Is that consistent here?" I need to verify this assumption. The key is to find all the places this `timeout` variable is used to see if the zero value always represents this state. I am going to see if the code is actually consistent with my understanding of `timeout = 0` being a flag for no timeout.

I'll specifically check where this variable is passed to `hmm_range_fault_unlocked_timeout`. The code snippet doesn't give me context, so the next logical step is to consult the larger codebase. I have a hunch, based on the grep output, that `tools/testing/selftests/mm/hmm-tests.c` might be relevant. Let me open that file and see how the timeout value is actually being used in conjunction with that function call. I need to understand the full picture to be certain about this timeout behavior.

{
  "File": "tools/testing/selftests/mm/hmm-tests.c",
  "FirstLine": 2950,
  "LineCount": 50
}

{
  "Contents": "2950:\t\t\t/* Test without THP */\n2951:\t\t\tASSERT_EQ(run_migration_benchmark(self-\u003efd, 0, test_sizes[i],\n2952:\t\t\t\t\t\titerations, \u0026regular_results), 0);\n2953:\t\n2954:\t\t\t/* Print results */\n2955:\t\t\tprint_benchmark_results(test_names[i], test_sizes[i],\n2956:\t\t\t\t\t\t\u0026thp_results, \u0026regular_results);\n2957:\t\t}\n2958:\t}\n2959:\t/*\n2960:\t * Test that HMM can fault in pages backed by userfaultfd using the\n2961:\t * hmm_range_fault_unlocked_timeout() path with no timeout. This exercises\n2962:\t * the lock-drop retry logic in the HMM framework.\n2963:\t */\n2964:\tstruct uffd_thread_args {\n2965:\t\tint uffd;\n2966:\t\tint stop_fd;\n2967:\t\tvoid *page_buffer;\n2968:\t\tunsigned long page_size;\n2969:\t};\n2970:\t\n2971:\tstatic void *uffd_handler_thread(void *arg)\n2972:\t{\n2973:\t\tstruct uffd_thread_args *args = arg;\n2974:\t\tstruct uffd_msg msg;\n2975:\t\tstruct uffdio_copy copy;\n2976:\t\tstruct pollfd pollfd[2];\n2977:\t\tint ret;\n2978:\t\n2979:\t\tpollfd[0].fd = args-\u003euffd;\n2980:\t\tpollfd[0].events = POLLIN;\n2981:\t\tpollfd[1].fd = args-\u003estop_fd;\n2982:\t\tpollfd[1].events = POLLIN;\n2983:\t\n2984:\t\twhile (1) {\n2985:\t\t\tret = poll(pollfd, 2, -1);\n2986:\t\t\tif (ret \u003c= 0)\n2987:\t\t\t\tbreak;\n2988:\t\t\tif (pollfd[1].revents)\n2989:\t\t\t\tbreak;\n2990:\t\t\tif (!(pollfd[0].revents \u0026 POLLIN))\n2991:\t\t\t\tbreak;\n2992:\t\n2993:\t\t\tret = read(args-\u003euffd, \u0026msg, sizeof(msg));\n2994:\t\t\tif (ret != sizeof(msg))\n2995:\t\t\t\tbreak;\n2996:\t\n2997:\t\t\tif (msg.event != UFFD_EVENT_PAGEFAULT)\n2998:\t\t\t\tbreak;\n2999:\t\n"
}

gemini-3.1-pro-preview

null

null

							input: 23948
							output: 24
							thoughts: 158
						

**Analyzing the HMM Timeout Change**

Okay, so I'm looking at this patch and my initial thought was about `hmm-tests.c` and that `hmm_range_fault_unlocked_timeout` function, specifically that it's being tested without any timeout. But that's just a test, and then I thought, "Hold on, `lib/test_hmm.c`...is that even *reachable* in a syzkaller context?"

Right, yes, it should be. `CONFIG_TEST_HMM` is typically enabled, and syzkaller *does* fuzz the `test_hmm` device, those `/dev/hmm_dmirror*` things. That's good. But now I'm seeing this patch is changing the `timeout` parameter or related logic in `aie2_ctx.c`, `drm_gpusvm.c`, and `nouveau_svm.c`, which are real, production drivers...and that's the key.

The patch *doesn't* touch `lib/test_hmm.c`, so whatever's happening with the timeout change isn't directly affecting that test. Okay, let's go back and look at the diff closely again. Need to make sure I'm not missing anything. I need to understand why these changes are being made and how they interact with syzkaller's coverage.

{
  "Expression": "hmm_range_fault_unlocked_timeout"
}

{
  "Output": "Documentation/mm/hmm.rst=160=normal interface is::\nDocumentation/mm/hmm.rst-161-\nDocumentation/mm/hmm.rst:162:  int hmm_range_fault_unlocked_timeout(struct hmm_range *range,\nDocumentation/mm/hmm.rst-163-                                       unsigned long timeout);\n--\nDocumentation/mm/hmm.rst=169=The caller must not hold ``mmap_read_lock`` before the call.\nDocumentation/mm/hmm.rst:170:``hmm_range_fault_unlocked_timeout()`` takes the mmap read lock internally and\nDocumentation/mm/hmm.rst-171-allows ``handle_mm_fault()`` to drop it during fault handling. This is required\n--\nDocumentation/mm/hmm.rst=186=The usage pattern is::\n--\nDocumentation/mm/hmm.rst-203- again:\nDocumentation/mm/hmm.rst:204:      ret = hmm_range_fault_unlocked_timeout(\u0026range, timeout);\nDocumentation/mm/hmm.rst-205-      if (ret)\n--\nDocumentation/mm/hmm.rst=228=update. The retry check must use the same notifier and sequence number stored\nDocumentation/mm/hmm.rst:229:in ``range`` by ``hmm_range_fault_unlocked_timeout()``.\nDocumentation/mm/hmm.rst-230-\nDocumentation/mm/hmm.rst=231=Holding the mmap lock across HMM faults\n--\nDocumentation/mm/hmm.rst-233-\nDocumentation/mm/hmm.rst:234:Most callers should use ``hmm_range_fault_unlocked_timeout()``. If a driver\nDocumentation/mm/hmm.rst-235-really needs to hold the mmap lock across work outside HMM, it can use::\n--\nDocumentation/mm/hmm.rst=240=interface cannot support VMAs whose fault handlers need to drop the mmap lock.\nDocumentation/mm/hmm.rst:241:New callers should prefer ``hmm_range_fault_unlocked_timeout()`` unless they\nDocumentation/mm/hmm.rst-242-have a specific requirement to keep the mmap lock held across the call.\n--\ndrivers/accel/amdxdna/aie2_ctx.c=1031=static int aie2_populate_range(struct amdxdna_gem_obj *abo)\n--\ndrivers/accel/amdxdna/aie2_ctx.c-1064-\ndrivers/accel/amdxdna/aie2_ctx.c:1065:\tret = hmm_range_fault_unlocked_timeout(\u0026mapp-\u003erange, timeout);\ndrivers/accel/amdxdna/aie2_ctx.c-1066-\tif (ret)\n--\ndrivers/gpu/drm/drm_gpusvm.c=841=enum drm_gpusvm_scan_result drm_gpusvm_scan_mm(struct drm_gpusvm_range *range,\n--\ndrivers/gpu/drm/drm_gpusvm.c-868-retry:\ndrivers/gpu/drm/drm_gpusvm.c:869:\terr = hmm_range_fault_unlocked_timeout(\u0026hmm_range, timeout);\ndrivers/gpu/drm/drm_gpusvm.c-870-\tif (err)\n--\ndrivers/gpu/drm/drm_gpusvm.c=1444=int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,\n--\ndrivers/gpu/drm/drm_gpusvm.c-1491-\thmm_range.hmm_pfns = pfns;\ndrivers/gpu/drm/drm_gpusvm.c:1492:\terr = hmm_range_fault_unlocked_timeout(\u0026hmm_range, timeout);\ndrivers/gpu/drm/drm_gpusvm.c-1493-\tmmput(mm);\n--\ndrivers/gpu/drm/drm_gpusvm.c=1703=int drm_gpusvm_range_evict(struct drm_gpusvm *gpusvm,\n--\ndrivers/gpu/drm/drm_gpusvm.c-1728-\thmm_range.hmm_pfns = pfns;\ndrivers/gpu/drm/drm_gpusvm.c:1729:\terr = hmm_range_fault_unlocked_timeout(\u0026hmm_range, timeout);\ndrivers/gpu/drm/drm_gpusvm.c-1730-\n--\ndrivers/gpu/drm/nouveau/nouveau_svm.c=652=static int nouveau_range_fault(struct nouveau_svmm *svmm,\n--\ndrivers/gpu/drm/nouveau/nouveau_svm.c-693-\ndrivers/gpu/drm/nouveau/nouveau_svm.c:694:\t\tret = hmm_range_fault_unlocked_timeout(\u0026range, remaining);\ndrivers/gpu/drm/nouveau/nouveau_svm.c-695-\t\tif (ret)\n--\ndrivers/hv/mshv_regions.c=396=static int mshv_region_range_fault(struct mshv_mem_region *region,\n--\ndrivers/hv/mshv_regions.c-415-again:\ndrivers/hv/mshv_regions.c:416:\tret = hmm_range_fault_unlocked_timeout(\u0026range, 0);\ndrivers/hv/mshv_regions.c-417-\tif (ret)\n--\ndrivers/infiniband/core/umem_odp.c=324=int ib_umem_odp_map_dma_and_lock(struct ib_umem_odp *umem_odp, u64 user_virt,\n--\ndrivers/infiniband/core/umem_odp.c-368-retry:\ndrivers/infiniband/core/umem_odp.c:369:\tret = hmm_range_fault_unlocked_timeout(\u0026range, timeout);\ndrivers/infiniband/core/umem_odp.c-370-\tif (unlikely(ret))\n--\ninclude/linux/hmm.h=125=int hmm_range_fault(struct hmm_range *range);\ninclude/linux/hmm.h:126:int hmm_range_fault_unlocked_timeout(struct hmm_range *range,\ninclude/linux/hmm.h-127-\t\t\t\t     unsigned long timeout);\n--\nlib/test_hmm.c=392=static int dmirror_range_fault_unlocked(struct dmirror *dmirror,\n--\nlib/test_hmm.c-398-\twhile (true) {\nlib/test_hmm.c:399:\t\tret = hmm_range_fault_unlocked_timeout(range, timeout);\nlib/test_hmm.c-400-\t\tif (ret)\n--\nmm/hmm.c=689=static int hmm_range_fault_locked(struct hmm_range *range, bool *locked)\n--\nmm/hmm.c-753- * The mmap lock must be held by the caller and will remain held on return.\nmm/hmm.c:754: * New users should prefer hmm_range_fault_unlocked_timeout() unless they\nmm/hmm.c-755- * specifically need to keep the mmap lock held across the call. This helper\n--\nmm/hmm.c=762=EXPORT_SYMBOL(hmm_range_fault);\n--\nmm/hmm.c-764-/**\nmm/hmm.c:765: * hmm_range_fault_unlocked_timeout - fault in a range with a retry timeout\nmm/hmm.c-766- * @range:\targument structure\n--\nmm/hmm.c-783- */\nmm/hmm.c:784:int hmm_range_fault_unlocked_timeout(struct hmm_range *range,\nmm/hmm.c-785-\t\t\t\t     unsigned long timeout)\n--\nmm/hmm.c-824-}\nmm/hmm.c:825:EXPORT_SYMBOL(hmm_range_fault_unlocked_timeout);\nmm/hmm.c-826-\n--\ntools/testing/selftests/mm/hmm-tests.c=2904=TEST_F_TIMEOUT(hmm, benchmark_thp_migration, 120)\n--\ntools/testing/selftests/mm/hmm-tests.c-2960- * Test that HMM can fault in pages backed by userfaultfd using the\ntools/testing/selftests/mm/hmm-tests.c:2961: * hmm_range_fault_unlocked_timeout() path with no timeout. This exercises\ntools/testing/selftests/mm/hmm-tests.c-2962- * the lock-drop retry logic in the HMM framework.\n"
}

gemini-3.1-pro-preview

null

null

							input: 26607
							output: 44
							thoughts: 56
						

**Investigating `hmm_range_fault_unlocked_timeout` in Infiniband's ODP Implementation**

Okay, so I've hit a point where I need to dig deeper into the Infiniband code, specifically looking at how the ODP (On Demand Paging) functionality is implemented. My initial concern stemmed from seeing `hmm_range_fault_unlocked_timeout` used in `drivers/infiniband/core/umem_odp.c`. This function name immediately raises a flag. It suggests we're dealing with memory faults or page faults within the user memory management, specifically within the context of ODP. The "unlocked" part means this probably happens without a lock held, which is significant from a concurrency and performance perspective. Given my expertise in this domain, my next step, as always, is to dive right into the code in `drivers/infiniband/core/umem_odp.c` to understand the exact mechanics of what's happening. I need to figure out what scenarios lead to this function being called and what the implications are regarding error handling, performance and race conditions within the ODP implementation. I'll be particularly interested in how they're handling potential timeout situations in relation to the memory faults.

{
  "File": "drivers/infiniband/core/umem_odp.c",
  "FirstLine": 350,
  "LineCount": 50
}

{
  "Contents": " 350:\t\t\tgoto out_put_task;\n 351:\t\t}\n 352:\t\n 353:\t\trange.notifier = \u0026umem_odp-\u003enotifier;\n 354:\t\trange.start = ALIGN_DOWN(user_virt, 1UL \u003c\u003c page_shift);\n 355:\t\trange.end = ALIGN(user_virt + bcnt, 1UL \u003c\u003c page_shift);\n 356:\t\tpfn_start_idx = (range.start - ib_umem_start(umem_odp)) \u003e\u003e PAGE_SHIFT;\n 357:\t\tnum_pfns = (range.end - range.start) \u003e\u003e PAGE_SHIFT;\n 358:\t\tif (fault) {\n 359:\t\t\trange.default_flags = HMM_PFN_REQ_FAULT;\n 360:\t\n 361:\t\t\tif (access_mask \u0026 HMM_PFN_WRITE)\n 362:\t\t\t\trange.default_flags |= HMM_PFN_REQ_WRITE;\n 363:\t\t}\n 364:\t\n 365:\t\trange.hmm_pfns = \u0026(umem_odp-\u003emap.pfn_list[pfn_start_idx]);\n 366:\t\ttimeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);\n 367:\t\n 368:\tretry:\n 369:\t\tret = hmm_range_fault_unlocked_timeout(\u0026range, timeout);\n 370:\t\tif (unlikely(ret))\n 371:\t\t\tgoto out_put_mm;\n 372:\t\n 373:\t\tstart_idx = (range.start - ib_umem_start(umem_odp)) \u003e\u003e page_shift;\n 374:\t\tdma_index = start_idx;\n 375:\t\n 376:\t\tmutex_lock(\u0026umem_odp-\u003eumem_mutex);\n 377:\t\tif (mmu_interval_read_retry(\u0026umem_odp-\u003enotifier, range.notifier_seq)) {\n 378:\t\t\tmutex_unlock(\u0026umem_odp-\u003eumem_mutex);\n 379:\t\t\tgoto retry;\n 380:\t\t}\n 381:\t\n 382:\t\tfor (pfn_index = 0; pfn_index \u003c num_pfns;\n 383:\t\t\tpfn_index += 1 \u003c\u003c (page_shift - PAGE_SHIFT), dma_index++) {\n 384:\t\n 385:\t\t\t/*\n 386:\t\t\t * Since we asked for hmm_range_fault() to populate\n 387:\t\t\t * pages it shouldn't return an error entry on success.\n 388:\t\t\t */\n 389:\t\t\tWARN_ON(fault \u0026\u0026 range.hmm_pfns[pfn_index] \u0026 HMM_PFN_ERROR);\n 390:\t\t\tWARN_ON(fault \u0026\u0026 !(range.hmm_pfns[pfn_index] \u0026 HMM_PFN_VALID));\n 391:\t\t\tif (!(range.hmm_pfns[pfn_index] \u0026 HMM_PFN_VALID))\n 392:\t\t\t\tcontinue;\n 393:\t\n 394:\t\t\tif (range.hmm_pfns[pfn_index] \u0026 HMM_PFN_DMA_MAPPED)\n 395:\t\t\t\tcontinue;\n 396:\t\n 397:\t\t\thmm_order = hmm_pfn_to_map_order(range.hmm_pfns[pfn_index]);\n 398:\t\t\t/* If a hugepage was detected and ODP wasn't set for, the umem\n 399:\t\t\t * page_shift will be used, the opposite case is an error.\n"
}

gemini-3.1-pro-preview

null

null

							input: 27920
							output: 20
							thoughts: 508
						

**Analyzing the Timeout Patch and Reachability in Syzkaller**

Okay, so the patch is about ensuring consistent timeout handling using `msecs_to_jiffies` across several drivers, and I see that `drivers/infiniband/core/umem_odp.c` already implements this correctly. It looks like the patch is correcting the implementation in `aie2_ctx.c`, `drm_gpusvm.c`, and `nouveau_svm.c` to match. 

The initial thought was to quickly assess `umem_odp.c` as an entry point since that lives in the Infiniband subsystem which *is* known to be reachable through `rdma` in syzkaller. However, since the patch does *not* modify `umem_odp.c`, that's not the relevant entry point here.

The real question becomes: are the affected drivers – `aie2_ctx.c`, `drm_gpusvm.c`, and `nouveau_svm.c` – reachable in syzkaller? Let's break them down:

*   `aie2_ctx.c`: `drivers/accel/amdxdna/aie2_ctx.c` – This requires AMD XDNA hardware.
*   `drm_gpusvm.c`: `drivers/gpu/drm/drm_gpusvm.c` – This is where things get interesting since this uses the `CONFIG_DRM_GPUSVM` which is selected by `DRM_XE`.
*   `nouveau_svm.c`: `drivers/gpu/drm/nouveau/nouveau_svm.c` – This requires NVIDIA hardware.

Now, checking the config, `drm_gpusvm.c` is compiled when `CONFIG_DRM_GPUSVM` is enabled and is selected by `DRM_XE`. The `DRM_XE` config requires PCI hardware which is, as expected, the Intel Xe hardware. But syzkaller doesn't have Intel Xe hardware in its VMs. The same applies for Nouveau (NVIDIA) and AMD XDNA hardware.

So, it doesn't look like we're directly reaching `drm_gpusvm.c` (and thus the fix) through hardware-dependent configurations. However, wait a minute, `drm_gpusvm.c` is a generic helper. Is it used by anything else? I need to double-check `CONFIG_DRM_GPUSVM` to see if there's any other route.

{
  "Expression": "select DRM_GPUSVM"
}

{
  "Output": "drivers/gpu/drm/xe/Kconfig=2=config DRM_XE\n--\ndrivers/gpu/drm/xe/Kconfig-41-\tselect DRM_EXEC\ndrivers/gpu/drm/xe/Kconfig:42:\tselect DRM_GPUSVM if !UML\ndrivers/gpu/drm/xe/Kconfig-43-\tselect DRM_GPUVM\n--\ndrivers/gpu/drm/xe/Kconfig=79=config DRM_XE_GPUSVM\n--\ndrivers/gpu/drm/xe/Kconfig-85-\tselect DEVICE_PRIVATE\ndrivers/gpu/drm/xe/Kconfig:86:\tselect DRM_GPUSVM\ndrivers/gpu/drm/xe/Kconfig-87-\thelp\n"
}

gemini-3.1-pro-preview

null

null

							input: 29182
							output: 17
							thoughts: 48
						

Okay, here's my take on those thoughts, framed as my own mental processing as an expert:

**Investigating the DRM_XE and DRM_GPUSVM Relationship**

Right, let me see... It looks like only `DRM_XE` is currently leveraging `DRM_GPUSVM`. That's a key observation. Now, a crucial question arises: can `DRM_XE` be accessed or tested without actual hardware present? This is important for development and CI. I need to figure out if there's a mock or virtual device implementation associated with `DRM_XE`. If there is, that opens up a whole range of possibilities for efficient testing and debugging in environments where physical hardware might not be readily available or convenient. Let's dig deeper and see if we can find those components.

no matches

{
  "Expression": "xe_mock"
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

null

null

							input: 29432
							output: 24
							thoughts: 125
						

**Investigating Hardware Emulation for the Patch**

Okay, so I need to figure out how to approach this patch. First, I'm thinking, can I trigger this `DRM_XE` behavior through a virtual PCI device? No dice, syzkaller doesn't emulate those Intel Xe GPUs. Alright, strike that. What about `nouveau`, the NVIDIA driver? Nope, syzkaller doesn't handle NVIDIA either. Shoot, not `amdxdna` either. Syzkaller is really limited in terms of GPU emulation.

Hmm, wait a second. This patch touches `Documentation/mm/hmm.rst`. That suggests it's not strictly GPU-specific. Okay, so I need to broaden my thinking. Is there *any* other driver out there that actually *uses* `hmm_range_fault_unlocked_timeout`? I need to know what else this patch touches to get the full scope. Okay, I found it: `drivers/hv/mshv_regions.c` uses it. Now I'm getting somewhere; at least I have a second point of reference. I have a lot more to look into.

You are repeating the same tool call with the exact same arguments. Please synthesize the information you already have instead of repeating queries.

{
  "Expression": "hmm_range_fault_unlocked_timeout"
}

{
  "error": "You are repeating the same tool call with the exact same arguments. Please synthesize the information you already have instead of repeating queries."
}

gemini-3.1-pro-preview

null

null

							input: 29888
							output: 19
							thoughts: 518
						

**Analyzing the Reachability of a Timeout Fix**

Okay, so I've just grepped for `hmm_range_fault_unlocked_timeout`, which flagged a few call sites. From the initial grep, I saw the following callers: `drivers/accel/amdxdna/aie2_ctx.c`, `drivers/gpu/drm/drm_gpusvm.c`, `drivers/gpu/drm/nouveau/nouveau_svm.c`, `drivers/hv/mshv_regions.c`, `drivers/infiniband/core/umem_odp.c`, `lib/test_hmm.c`, and `tools/testing/selftests/mm/hmm-tests.c`.

Now, the patch itself only touches `Documentation/mm/hmm.rst`, `drivers/accel/amdxdna/aie2_ctx.c`, `drivers/gpu/drm/drm_gpusvm.c`, and `drivers/gpu/drm/nouveau/nouveau_svm.c`. The core question now is, are these modified paths reachable within a typical virtualized environment like GCE or QEMU, which syzkaller primarily uses?

Considering the devices these drivers target - AMD XDNA, Intel Xe, and NVIDIA – and the fact that Syzkaller lacks emulation for these specific hardware components, it looks unlikely. Let's delve deeper.

`drm_gpusvm.c` is only selected by `DRM_XE`. The others are PCI drivers. Without specific hardware, it's a dead end. Therefore, no `nouveau`, `amdxdna`, or `DRM_XE` are reachable. What about the untouched files? `mshv_regions.c` is Hyper-V, so it's irrelevant. `umem_odp.c` and `test_hmm.c` also go untouched.

So, it appears the patch exclusively modifies code paths that are inherently inaccessible in common virtualization scenarios. We're effectively looking at hardware-dependent functionality that syzkaller likely won't trigger. I will double check my assumptions.

Okay, let me confirm. Can `nouveau` possibly be probed without the hardware? It's a PCI driver. Without an NVIDIA PCI device present, the driver won't bind and its ioctls become inaccessible. Same for the others.

Is it *possible* that `drm_gpusvm` is tested via some other means, like a kunit test? That's what I need to check next.

{
  "Expression": "drm_gpusvm"
}

{
  "Output": "\nFull output is too long, showing 500 out of 1682 lines.\nUse more precise expression if possible.\n\n.clang-format=71=ForEachMacros:\n--\n.clang-format-182-  - 'drm_gem_for_each_gpuvm_bo_safe'\n.clang-format:183:  - 'drm_gpusvm_for_each_range'\n.clang-format-184-  - 'drm_gpuva_for_each_op'\n--\nDocumentation/gpu/rfc/gpusvm.rst=67=Overview of baseline design\n--\nDocumentation/gpu/rfc/gpusvm.rst-69-\nDocumentation/gpu/rfc/gpusvm.rst:70:.. kernel-doc:: drivers/gpu/drm/drm_gpusvm.c\nDocumentation/gpu/rfc/gpusvm.rst-71-   :doc: Overview\nDocumentation/gpu/rfc/gpusvm.rst-72-\nDocumentation/gpu/rfc/gpusvm.rst:73:.. kernel-doc:: drivers/gpu/drm/drm_gpusvm.c\nDocumentation/gpu/rfc/gpusvm.rst-74-   :doc: Locking\nDocumentation/gpu/rfc/gpusvm.rst-75-\nDocumentation/gpu/rfc/gpusvm.rst:76:.. kernel-doc:: drivers/gpu/drm/drm_gpusvm.c\nDocumentation/gpu/rfc/gpusvm.rst-77-   :doc: Partial Unmapping of Ranges\nDocumentation/gpu/rfc/gpusvm.rst-78-\nDocumentation/gpu/rfc/gpusvm.rst:79:.. kernel-doc:: drivers/gpu/drm/drm_gpusvm.c\nDocumentation/gpu/rfc/gpusvm.rst-80-   :doc: Examples\n--\nDocumentation/gpu/rfc/gpusvm.rst=91=Possible future design features\n--\nDocumentation/gpu/rfc/gpusvm.rst-100-* Ranges with mixed system and device pages\nDocumentation/gpu/rfc/gpusvm.rst:101:\t* Can be added if required to drm_gpusvm_get_pages fairly easily.\nDocumentation/gpu/rfc/gpusvm.rst-102-* Multi-GPU support\n--\nNext/merge.log=1458=Merge made by the 'ort' strategy.\n--\nNext/merge.log-1512- drivers/base/arch_numa.c                           |   4 -\nNext/merge.log:1513: drivers/gpu/drm/drm_gpusvm.c                       |  52 +-\nNext/merge.log-1514- drivers/gpu/drm/etnaviv/etnaviv_gem.c              |   3 +-\n--\nNext/merge.log=5452=$ git merge -m Merge branch 'for-linux-next' of https://gitlab.freedesktop.org/drm/misc/kernel.git drm-misc/for-linux-next\nNext/merge.log:5453:Auto-merging drivers/gpu/drm/drm_gpusvm.c\nNext/merge.log-5454-Auto-merging drivers/gpu/drm/xe/xe_pt.c\nNext/merge.log=5455=Merge made by the 'ort' strategy.\nNext/merge.log:5456: drivers/gpu/drm/drm_gpusvm.c                       | 243 ++++++++++++---------\nNext/merge.log-5457- .../gpu/drm/nouveau/nvkm/subdev/gsp/rm/r535/fbsr.c |   1 +\n--\nNext/merge.log-5468- drivers/gpu/drm/xe/xe_userptr.c                    |   5 +-\nNext/merge.log:5469: include/drm/drm_gpusvm.h                           |  67 ++++--\nNext/merge.log-5470- 14 files changed, 350 insertions(+), 218 deletions(-)\n--\ndrivers/gpu/drm/Makefile=107=obj-$(CONFIG_DRM_GPUVM) += drm_gpuvm.o\ndrivers/gpu/drm/Makefile-108-\ndrivers/gpu/drm/Makefile:109:drm_gpusvm_helper-y := \\\ndrivers/gpu/drm/Makefile:110:\tdrm_gpusvm.o\ndrivers/gpu/drm/Makefile:111:drm_gpusvm_helper-$(CONFIG_ZONE_DEVICE) += \\\ndrivers/gpu/drm/Makefile-112-\tdrm_pagemap.o\\\n--\ndrivers/gpu/drm/Makefile-114-\ndrivers/gpu/drm/Makefile:115:obj-$(CONFIG_DRM_GPUSVM) += drm_gpusvm_helper.o\ndrivers/gpu/drm/Makefile-116-\n--\ndrivers/gpu/drm/drm_gpusvm.c-17-#include \u003cdrm/drm_device.h\u003e\ndrivers/gpu/drm/drm_gpusvm.c:18:#include \u003cdrm/drm_gpusvm.h\u003e\ndrivers/gpu/drm/drm_gpusvm.c-19-#include \u003cdrm/drm_pagemap.h\u003e\n--\ndrivers/gpu/drm/drm_gpusvm.c-51- * - Pages:\ndrivers/gpu/drm/drm_gpusvm.c:52: *\tstruct drm_gpusvm_pages holds the DMA mapping state for a range of\ndrivers/gpu/drm/drm_gpusvm.c-53- *\tCPU virtual addresses: the DMA mapped device addresses,\n--\ndrivers/gpu/drm/drm_gpusvm.c-56- *\tmappings.\ndrivers/gpu/drm/drm_gpusvm.c:57: *\tA driver embeds one or more struct drm_gpusvm_pages alongside its\ndrivers/gpu/drm/drm_gpusvm.c:58: *\tstruct drm_gpusvm_range, choosing one of two layouts:\ndrivers/gpu/drm/drm_gpusvm.c-59- *\ndrivers/gpu/drm/drm_gpusvm.c:60: *\t1:1 - one drm_gpusvm_pages per range (one drm_device). Simplest\ndrivers/gpu/drm/drm_gpusvm.c-61- *\tlayout; to mirror a VA range on several devices a driver uses a\n--\ndrivers/gpu/drm/drm_gpusvm.c-64- *\ndrivers/gpu/drm/drm_gpusvm.c:65: *\tN:1 - one drm_gpusvm_pages per drm_device, all sharing one range and\ndrivers/gpu/drm/drm_gpusvm.c-66- *\tnotifier; only the per-device DMA mapping differs. The instances must\ndrivers/gpu/drm/drm_gpusvm.c:67: *\tsit in contiguous memory so a single drm_gpusvm_range_set_unmapped()\ndrivers/gpu/drm/drm_gpusvm.c-68- *\tcan mark them all. A driver can keep one instance inline for the single\n--\ndrivers/gpu/drm/drm_gpusvm.c-74- *\t\tstruct driver_range {\ndrivers/gpu/drm/drm_gpusvm.c:75: *\t\t\tstruct drm_gpusvm_range base;\ndrivers/gpu/drm/drm_gpusvm.c-76- *\t\t\tunsigned int num_pages;\t// 1: inline_pages, \u003e1: pages[]\ndrivers/gpu/drm/drm_gpusvm.c-77- *\t\t\tunion {\ndrivers/gpu/drm/drm_gpusvm.c:78: *\t\t\t\tstruct drm_gpusvm_pages inline_pages;\ndrivers/gpu/drm/drm_gpusvm.c:79: *\t\t\t\tstruct drm_gpusvm_pages *pages;\ndrivers/gpu/drm/drm_gpusvm.c-80- *\t\t\t};\n--\ndrivers/gpu/drm/drm_gpusvm.c-84- *\tallocator (e.g. kcalloc(num_pages, ...)), initialises each entry with\ndrivers/gpu/drm/drm_gpusvm.c:85: *\tdrm_gpusvm_init_pages(), and frees each entry with\ndrivers/gpu/drm/drm_gpusvm.c:86: *\tdrm_gpusvm_free_pages() plus the array itself, from its range free\ndrivers/gpu/drm/drm_gpusvm.c:87: *\tcallback. Each drm_gpusvm_pages is mapped independently by their own\ndrivers/gpu/drm/drm_gpusvm.c-88- *\tdrm_device.\ndrivers/gpu/drm/drm_gpusvm.c:89: *\tEach drm_gpusvm_pages must be zero-initialised and initialised with\ndrivers/gpu/drm/drm_gpusvm.c:90: *\tdrm_gpusvm_init_pages(), called once per entry.\ndrivers/gpu/drm/drm_gpusvm.c-91- *\n--\ndrivers/gpu/drm/drm_gpusvm.c-135- * except for the recheck range's pages being valid\ndrivers/gpu/drm/drm_gpusvm.c:136: * (drm_gpusvm_pages_valid) when the driver is committing GPU bindings.\ndrivers/gpu/drm/drm_gpusvm.c-137- * This lock corresponds to the ``driver-\u003eupdate`` lock mentioned in\n--\ndrivers/gpu/drm/drm_gpusvm.c-143- * lock to safeguard core GPU SVM function calls that modify state, such as\ndrivers/gpu/drm/drm_gpusvm.c:144: * drm_gpusvm_range_find_or_insert and drm_gpusvm_range_remove. This lock is\ndrivers/gpu/drm/drm_gpusvm.c-145- * denoted as 'driver_svm_lock' in code examples. Finer grained driver side\ndrivers/gpu/drm/drm_gpusvm.c-146- * locking should also be possible for concurrent GPU fault processing within a\ndrivers/gpu/drm/drm_gpusvm.c:147: * single GPU SVM. The 'driver_svm_lock' can be via drm_gpusvm_driver_set_lock\ndrivers/gpu/drm/drm_gpusvm.c-148- * to add annotations to GPU SVM.\n--\ndrivers/gpu/drm/drm_gpusvm.c-184- *\tstruct driver_range {\ndrivers/gpu/drm/drm_gpusvm.c:185: *\t\tstruct drm_gpusvm_range base;\ndrivers/gpu/drm/drm_gpusvm.c:186: *\t\tstruct drm_gpusvm_pages pages;\ndrivers/gpu/drm/drm_gpusvm.c-187- *\t};\ndrivers/gpu/drm/drm_gpusvm.c-188- *\ndrivers/gpu/drm/drm_gpusvm.c:189: *\tint driver_bind_range(struct drm_gpusvm *gpusvm, struct driver_range *drange)\ndrivers/gpu/drm/drm_gpusvm.c-190- *\t{\n--\ndrivers/gpu/drm/drm_gpusvm.c-194- *\ndrivers/gpu/drm/drm_gpusvm.c:195: *\t\tdrm_gpusvm_notifier_lock(gpusvm);\ndrivers/gpu/drm/drm_gpusvm.c:196: *\t\tif (drm_gpusvm_pages_valid(gpusvm, \u0026drange-\u003epages))\ndrivers/gpu/drm/drm_gpusvm.c-197- *\t\t\tdriver_commit_bind(gpusvm, drange);\n--\ndrivers/gpu/drm/drm_gpusvm.c-199- *\t\t\terr = -EAGAIN;\ndrivers/gpu/drm/drm_gpusvm.c:200: *\t\tdrm_gpusvm_notifier_unlock(gpusvm);\ndrivers/gpu/drm/drm_gpusvm.c-201- *\n--\ndrivers/gpu/drm/drm_gpusvm.c-204- *\ndrivers/gpu/drm/drm_gpusvm.c:205: *\tint driver_gpu_fault(struct drm_gpusvm *gpusvm, unsigned long fault_addr,\ndrivers/gpu/drm/drm_gpusvm.c-206- *\t\t\t     unsigned long gpuva_start, unsigned long gpuva_end)\ndrivers/gpu/drm/drm_gpusvm.c-207- *\t{\ndrivers/gpu/drm/drm_gpusvm.c:208: *\t\tstruct drm_gpusvm_ctx ctx = {};\ndrivers/gpu/drm/drm_gpusvm.c-209- *\t\tstruct driver_range *drange;\ndrivers/gpu/drm/drm_gpusvm.c:210: *\t\tstruct drm_gpusvm_range *range;\ndrivers/gpu/drm/drm_gpusvm.c-211- *\t\tint err;\n--\ndrivers/gpu/drm/drm_gpusvm.c-217- *\ndrivers/gpu/drm/drm_gpusvm.c:218: *\t\trange = drm_gpusvm_range_find_or_insert(gpusvm, fault_addr,\ndrivers/gpu/drm/drm_gpusvm.c-219- *\t\t\t\t\t\t\tgpuva_start, gpuva_end,\n--\ndrivers/gpu/drm/drm_gpusvm.c-234- *\ndrivers/gpu/drm/drm_gpusvm.c:235: *\t\terr = drm_gpusvm_get_pages(gpusvm, \u0026drange-\u003epages,\ndrivers/gpu/drm/drm_gpusvm.c-236- *\t\t\t\t\t   gpusvm-\u003emm, \u0026range-\u003enotifier-\u003enotifier,\ndrivers/gpu/drm/drm_gpusvm.c:237: *\t\t\t\t\t   drm_gpusvm_range_start(range),\ndrivers/gpu/drm/drm_gpusvm.c:238: *\t\t\t\t\t   drm_gpusvm_range_end(range), \u0026ctx);\ndrivers/gpu/drm/drm_gpusvm.c-239- *\t\tif (err == -EOPNOTSUPP || err == -EFAULT || err == -EPERM) {\t// CPU mappings changed\ndrivers/gpu/drm/drm_gpusvm.c-240- *\t\t\tif (err == -EOPNOTSUPP)\ndrivers/gpu/drm/drm_gpusvm.c:241: *\t\t\t\tdrm_gpusvm_range_evict(gpusvm, range);\ndrivers/gpu/drm/drm_gpusvm.c-242- *\t\t\tgoto retry;\n--\ndrivers/gpu/drm/drm_gpusvm.c-259- *\ndrivers/gpu/drm/drm_gpusvm.c:260: *\t// The driver owns the drm_gpusvm_pages lifecycle. ops-\u003erange_free is\ndrivers/gpu/drm/drm_gpusvm.c:261: *\t// the final fallback: drm_gpusvm_free_pages() unmaps any\ndrivers/gpu/drm/drm_gpusvm.c-262- *\t// lingering DMA mapping and a no-op if already unmapped and frees the\ndrivers/gpu/drm/drm_gpusvm.c-263- *\t// dma_addr array. The normal flow is to DMA unmap before\ndrivers/gpu/drm/drm_gpusvm.c:264: *\t// drm_gpusvm_range_remove() (before the range leaves the tree).\ndrivers/gpu/drm/drm_gpusvm.c:265: *\tvoid driver_range_free(struct drm_gpusvm_range *range)\ndrivers/gpu/drm/drm_gpusvm.c-266- *\t{\n--\ndrivers/gpu/drm/drm_gpusvm.c-269- *\ndrivers/gpu/drm/drm_gpusvm.c:270: *\t\tdrm_gpusvm_free_pages(range-\u003egpusvm, \u0026drange-\u003epages,\ndrivers/gpu/drm/drm_gpusvm.c:271: *\t\t\t\t      drm_gpusvm_range_size(range) \u003e\u003e PAGE_SHIFT);\ndrivers/gpu/drm/drm_gpusvm.c-272- *\t\tkfree(drange);\n--\ndrivers/gpu/drm/drm_gpusvm.c-274- *\ndrivers/gpu/drm/drm_gpusvm.c:275: *\tvoid __driver_garbage_collector(struct drm_gpusvm *gpusvm,\ndrivers/gpu/drm/drm_gpusvm.c:276: *\t\t\t\t\tstruct drm_gpusvm_range *range)\ndrivers/gpu/drm/drm_gpusvm.c-277- *\t{\n--\ndrivers/gpu/drm/drm_gpusvm.c-281- *\t\tif (range-\u003eflags.partial_unmap)\ndrivers/gpu/drm/drm_gpusvm.c:282: *\t\t\tdrm_gpusvm_range_evict(gpusvm, range);\ndrivers/gpu/drm/drm_gpusvm.c-283- *\ndrivers/gpu/drm/drm_gpusvm.c-284- *\t\tdriver_unbind_range(range);\ndrivers/gpu/drm/drm_gpusvm.c:285: *\t\t// The pages must be DMA unmapped before drm_gpusvm_range_remove()\ndrivers/gpu/drm/drm_gpusvm.c-286- *\t\t// , so a range is never off the MMU interval tree while still DMA\n--\ndrivers/gpu/drm/drm_gpusvm.c-289- *\t\t// for device DMA. This is the normal unmap point.\ndrivers/gpu/drm/drm_gpusvm.c:290: *\t\tdrm_gpusvm_unmap_pages(gpusvm, \u0026drange-\u003epages,\ndrivers/gpu/drm/drm_gpusvm.c:291: *\t\t\t\t       drm_gpusvm_range_size(range) \u003e\u003e PAGE_SHIFT,\ndrivers/gpu/drm/drm_gpusvm.c:292: *\t\t\t\t       \u0026(struct drm_gpusvm_ctx){ .in_notifier = false });\ndrivers/gpu/drm/drm_gpusvm.c:293: *\t\tdrm_gpusvm_range_remove(gpusvm, range);\ndrivers/gpu/drm/drm_gpusvm.c-294- *\t}\ndrivers/gpu/drm/drm_gpusvm.c-295- *\ndrivers/gpu/drm/drm_gpusvm.c:296: *\tvoid driver_garbage_collector(struct drm_gpusvm *gpusvm)\ndrivers/gpu/drm/drm_gpusvm.c-297- *\t{\n--\ndrivers/gpu/drm/drm_gpusvm.c-307- *\ndrivers/gpu/drm/drm_gpusvm.c:308: *\tvoid driver_invalidation(struct drm_gpusvm *gpusvm,\ndrivers/gpu/drm/drm_gpusvm.c:309: *\t\t\t\t struct drm_gpusvm_notifier *notifier,\ndrivers/gpu/drm/drm_gpusvm.c-310- *\t\t\t\t const struct mmu_notifier_range *mmu_range)\ndrivers/gpu/drm/drm_gpusvm.c-311- *\t{\ndrivers/gpu/drm/drm_gpusvm.c:312: *\t\tstruct drm_gpusvm_ctx ctx = { .in_notifier = true, };\ndrivers/gpu/drm/drm_gpusvm.c:313: *\t\tstruct drm_gpusvm_range *range = NULL;\ndrivers/gpu/drm/drm_gpusvm.c-314- *\t\tstruct driver_range *drange;\n--\ndrivers/gpu/drm/drm_gpusvm.c-317- *\ndrivers/gpu/drm/drm_gpusvm.c:318: *\t\tdrm_gpusvm_for_each_range(range, notifier, mmu_range-\u003estart,\ndrivers/gpu/drm/drm_gpusvm.c-319- *\t\t\t\t\t  mmu_range-\u003eend) {\n--\ndrivers/gpu/drm/drm_gpusvm.c-321- *\ndrivers/gpu/drm/drm_gpusvm.c:322: *\t\t\tdrm_gpusvm_unmap_pages(gpusvm, \u0026drange-\u003epages,\ndrivers/gpu/drm/drm_gpusvm.c:323: *\t\t\t\t\t       drm_gpusvm_range_size(range) \u003e\u003e PAGE_SHIFT,\ndrivers/gpu/drm/drm_gpusvm.c-324- *\t\t\t\t\t       \u0026ctx);\n--\ndrivers/gpu/drm/drm_gpusvm.c-328- *\ndrivers/gpu/drm/drm_gpusvm.c:329: *\t\t\tdrm_gpusvm_range_set_unmapped(range, \u0026drange-\u003epages, 1, mmu_range);\ndrivers/gpu/drm/drm_gpusvm.c-330- *\t\t\tdriver_garbage_collector_add(gpusvm, range);\n--\ndrivers/gpu/drm/drm_gpusvm.c=348=npages_in_range(unsigned long start, unsigned long end)\n--\ndrivers/gpu/drm/drm_gpusvm.c-353-/**\ndrivers/gpu/drm/drm_gpusvm.c:354: * drm_gpusvm_notifier_find() - Find GPU SVM notifier from GPU SVM\ndrivers/gpu/drm/drm_gpusvm.c-355- * @gpusvm: Pointer to the GPU SVM structure.\n--\ndrivers/gpu/drm/drm_gpusvm.c-358- *\ndrivers/gpu/drm/drm_gpusvm.c:359: * Return: A pointer to the drm_gpusvm_notifier if found or NULL\ndrivers/gpu/drm/drm_gpusvm.c-360- */\ndrivers/gpu/drm/drm_gpusvm.c:361:struct drm_gpusvm_notifier *\ndrivers/gpu/drm/drm_gpusvm.c:362:drm_gpusvm_notifier_find(struct drm_gpusvm *gpusvm, unsigned long start,\ndrivers/gpu/drm/drm_gpusvm.c-363-\t\t\t unsigned long end)\n--\ndrivers/gpu/drm/drm_gpusvm.c-369-\tif (itree)\ndrivers/gpu/drm/drm_gpusvm.c:370:\t\treturn container_of(itree, struct drm_gpusvm_notifier, itree);\ndrivers/gpu/drm/drm_gpusvm.c-371-\telse\n--\ndrivers/gpu/drm/drm_gpusvm.c-373-}\ndrivers/gpu/drm/drm_gpusvm.c:374:EXPORT_SYMBOL_GPL(drm_gpusvm_notifier_find);\ndrivers/gpu/drm/drm_gpusvm.c-375-\ndrivers/gpu/drm/drm_gpusvm.c-376-/**\ndrivers/gpu/drm/drm_gpusvm.c:377: * drm_gpusvm_range_find() - Find GPU SVM range from GPU SVM notifier\ndrivers/gpu/drm/drm_gpusvm.c-378- * @notifier: Pointer to the GPU SVM notifier structure.\n--\ndrivers/gpu/drm/drm_gpusvm.c-381- *\ndrivers/gpu/drm/drm_gpusvm.c:382: * Return: A pointer to the drm_gpusvm_range if found or NULL\ndrivers/gpu/drm/drm_gpusvm.c-383- */\ndrivers/gpu/drm/drm_gpusvm.c:384:struct drm_gpusvm_range *\ndrivers/gpu/drm/drm_gpusvm.c:385:drm_gpusvm_range_find(struct drm_gpusvm_notifier *notifier, unsigned long start,\ndrivers/gpu/drm/drm_gpusvm.c-386-\t\t      unsigned long end)\n--\ndrivers/gpu/drm/drm_gpusvm.c-392-\tif (itree)\ndrivers/gpu/drm/drm_gpusvm.c:393:\t\treturn container_of(itree, struct drm_gpusvm_range, itree);\ndrivers/gpu/drm/drm_gpusvm.c-394-\telse\n--\ndrivers/gpu/drm/drm_gpusvm.c-396-}\ndrivers/gpu/drm/drm_gpusvm.c:397:EXPORT_SYMBOL_GPL(drm_gpusvm_range_find);\ndrivers/gpu/drm/drm_gpusvm.c-398-\ndrivers/gpu/drm/drm_gpusvm.c-399-/**\ndrivers/gpu/drm/drm_gpusvm.c:400: * drm_gpusvm_notifier_invalidate() - Invalidate a GPU SVM notifier.\ndrivers/gpu/drm/drm_gpusvm.c-401- * @mni: Pointer to the mmu_interval_notifier structure.\n--\ndrivers/gpu/drm/drm_gpusvm.c=411=static bool\ndrivers/gpu/drm/drm_gpusvm.c:412:drm_gpusvm_notifier_invalidate(struct mmu_interval_notifier *mni,\ndrivers/gpu/drm/drm_gpusvm.c-413-\t\t\t       const struct mmu_notifier_range *mmu_range,\n--\ndrivers/gpu/drm/drm_gpusvm.c-415-{\ndrivers/gpu/drm/drm_gpusvm.c:416:\tstruct drm_gpusvm_notifier *notifier =\ndrivers/gpu/drm/drm_gpusvm.c-417-\t\tcontainer_of(mni, typeof(*notifier), notifier);\ndrivers/gpu/drm/drm_gpusvm.c:418:\tstruct drm_gpusvm *gpusvm = notifier-\u003egpusvm;\ndrivers/gpu/drm/drm_gpusvm.c-419-\n--\ndrivers/gpu/drm/drm_gpusvm.c-431-/*\ndrivers/gpu/drm/drm_gpusvm.c:432: * drm_gpusvm_notifier_ops - MMU interval notifier operations for GPU SVM\ndrivers/gpu/drm/drm_gpusvm.c-433- */\ndrivers/gpu/drm/drm_gpusvm.c:434:static const struct mmu_interval_notifier_ops drm_gpusvm_notifier_ops = {\ndrivers/gpu/drm/drm_gpusvm.c:435:\t.invalidate = drm_gpusvm_notifier_invalidate,\ndrivers/gpu/drm/drm_gpusvm.c-436-};\n--\ndrivers/gpu/drm/drm_gpusvm.c-438-/**\ndrivers/gpu/drm/drm_gpusvm.c:439: * drm_gpusvm_init() - Initialize the GPU SVM.\ndrivers/gpu/drm/drm_gpusvm.c-440- * @gpusvm: Pointer to the GPU SVM structure.\n--\ndrivers/gpu/drm/drm_gpusvm.c-453- *\ndrivers/gpu/drm/drm_gpusvm.c:454: * Note: If only using the simple drm_gpusvm_pages API (get/unmap/free),\ndrivers/gpu/drm/drm_gpusvm.c-455- * then only @gpusvm and @name are expected. The @drm drm_device for dma\ndrivers/gpu/drm/drm_gpusvm.c:456: * mappings is bound per-pages via drm_gpusvm_init_pages() before the first\ndrivers/gpu/drm/drm_gpusvm.c:457: * drm_gpusvm_get_pages() call. However, the same base\ndrivers/gpu/drm/drm_gpusvm.c-458- * @gpusvm can also be used with both modes together in which case the full\ndrivers/gpu/drm/drm_gpusvm.c:459: * setup is needed, where the core drm_gpusvm_pages API will simply never use\ndrivers/gpu/drm/drm_gpusvm.c-460- * the other fields.\n--\ndrivers/gpu/drm/drm_gpusvm.c-463- */\ndrivers/gpu/drm/drm_gpusvm.c:464:int drm_gpusvm_init(struct drm_gpusvm *gpusvm,\ndrivers/gpu/drm/drm_gpusvm.c-465-\t\t    const char *name,\n--\ndrivers/gpu/drm/drm_gpusvm.c-468-\t\t    unsigned long notifier_size,\ndrivers/gpu/drm/drm_gpusvm.c:469:\t\t    const struct drm_gpusvm_ops *ops,\ndrivers/gpu/drm/drm_gpusvm.c-470-\t\t    const unsigned long *chunk_sizes, int num_chunks)\n--\ndrivers/gpu/drm/drm_gpusvm.c-476-\t} else {\ndrivers/gpu/drm/drm_gpusvm.c:477:\t\t/* No full SVM mode, only core drm_gpusvm_pages API. */\ndrivers/gpu/drm/drm_gpusvm.c-478-\t\tif (ops || num_chunks || mm_range || notifier_size)\n--\ndrivers/gpu/drm/drm_gpusvm.c-505-}\ndrivers/gpu/drm/drm_gpusvm.c:506:EXPORT_SYMBOL_GPL(drm_gpusvm_init);\ndrivers/gpu/drm/drm_gpusvm.c-507-\ndrivers/gpu/drm/drm_gpusvm.c-508-/**\ndrivers/gpu/drm/drm_gpusvm.c:509: * to_drm_gpusvm_notifier() - retrieve the container struct for a given rbtree node\ndrivers/gpu/drm/drm_gpusvm.c:510: * @node: a pointer to the rbtree node embedded within a drm_gpusvm_notifier struct\ndrivers/gpu/drm/drm_gpusvm.c-511- *\ndrivers/gpu/drm/drm_gpusvm.c:512: * Return: A pointer to the containing drm_gpusvm_notifier structure.\ndrivers/gpu/drm/drm_gpusvm.c-513- */\ndrivers/gpu/drm/drm_gpusvm.c:514:static struct drm_gpusvm_notifier *to_drm_gpusvm_notifier(struct rb_node *node)\ndrivers/gpu/drm/drm_gpusvm.c-515-{\ndrivers/gpu/drm/drm_gpusvm.c:516:\treturn container_of(node, struct drm_gpusvm_notifier, itree.rb);\ndrivers/gpu/drm/drm_gpusvm.c-517-}\n--\ndrivers/gpu/drm/drm_gpusvm.c-519-/**\ndrivers/gpu/drm/drm_gpusvm.c:520: * drm_gpusvm_notifier_insert() - Insert GPU SVM notifier\ndrivers/gpu/drm/drm_gpusvm.c-521- * @gpusvm: Pointer to the GPU SVM structure\n--\ndrivers/gpu/drm/drm_gpusvm.c-525- */\ndrivers/gpu/drm/drm_gpusvm.c:526:static void drm_gpusvm_notifier_insert(struct drm_gpusvm *gpusvm,\ndrivers/gpu/drm/drm_gpusvm.c:527:\t\t\t\t       struct drm_gpusvm_notifier *notifier)\ndrivers/gpu/drm/drm_gpusvm.c-528-{\n--\ndrivers/gpu/drm/drm_gpusvm.c-535-\tif (node)\ndrivers/gpu/drm/drm_gpusvm.c:536:\t\thead = \u0026(to_drm_gpusvm_notifier(node))-\u003eentry;\ndrivers/gpu/drm/drm_gpusvm.c-537-\telse\n--\ndrivers/gpu/drm/drm_gpusvm.c-543-/**\ndrivers/gpu/drm/drm_gpusvm.c:544: * drm_gpusvm_notifier_remove() - Remove GPU SVM notifier\ndrivers/gpu/drm/drm_gpusvm.c-545- * @gpusvm: Pointer to the GPU SVM tructure\n--\ndrivers/gpu/drm/drm_gpusvm.c-549- */\ndrivers/gpu/drm/drm_gpusvm.c:550:static void drm_gpusvm_notifier_remove(struct drm_gpusvm *gpusvm,\ndrivers/gpu/drm/drm_gpusvm.c:551:\t\t\t\t       struct drm_gpusvm_notifier *notifier)\ndrivers/gpu/drm/drm_gpusvm.c-552-{\n--\ndrivers/gpu/drm/drm_gpusvm.c-557-/**\ndrivers/gpu/drm/drm_gpusvm.c:558: * drm_gpusvm_fini() - Finalize the GPU SVM.\ndrivers/gpu/drm/drm_gpusvm.c-559- * @gpusvm: Pointer to the GPU SVM structure.\n--\ndrivers/gpu/drm/drm_gpusvm.c-563- */\ndrivers/gpu/drm/drm_gpusvm.c:564:void drm_gpusvm_fini(struct drm_gpusvm *gpusvm)\ndrivers/gpu/drm/drm_gpusvm.c-565-{\ndrivers/gpu/drm/drm_gpusvm.c:566:\tstruct drm_gpusvm_notifier *notifier, *next;\ndrivers/gpu/drm/drm_gpusvm.c-567-\ndrivers/gpu/drm/drm_gpusvm.c:568:\tdrm_gpusvm_for_each_notifier_safe(notifier, next, gpusvm, 0, LONG_MAX) {\ndrivers/gpu/drm/drm_gpusvm.c:569:\t\tstruct drm_gpusvm_range *range, *__next;\ndrivers/gpu/drm/drm_gpusvm.c-570-\n--\ndrivers/gpu/drm/drm_gpusvm.c-576-\ndrivers/gpu/drm/drm_gpusvm.c:577:\t\tdrm_gpusvm_for_each_range_safe(range, __next, notifier, 0,\ndrivers/gpu/drm/drm_gpusvm.c-578-\t\t\t\t\t       LONG_MAX)\ndrivers/gpu/drm/drm_gpusvm.c:579:\t\t\tdrm_gpusvm_range_remove(gpusvm, range);\ndrivers/gpu/drm/drm_gpusvm.c-580-\t}\n--\ndrivers/gpu/drm/drm_gpusvm.c-585-}\ndrivers/gpu/drm/drm_gpusvm.c:586:EXPORT_SYMBOL_GPL(drm_gpusvm_fini);\ndrivers/gpu/drm/drm_gpusvm.c-587-\ndrivers/gpu/drm/drm_gpusvm.c-588-/**\ndrivers/gpu/drm/drm_gpusvm.c:589: * drm_gpusvm_notifier_alloc() - Allocate GPU SVM notifier\ndrivers/gpu/drm/drm_gpusvm.c-590- * @gpusvm: Pointer to the GPU SVM structure\n--\ndrivers/gpu/drm/drm_gpusvm.c-596- */\ndrivers/gpu/drm/drm_gpusvm.c:597:static struct drm_gpusvm_notifier *\ndrivers/gpu/drm/drm_gpusvm.c:598:drm_gpusvm_notifier_alloc(struct drm_gpusvm *gpusvm, unsigned long fault_addr)\ndrivers/gpu/drm/drm_gpusvm.c-599-{\ndrivers/gpu/drm/drm_gpusvm.c:600:\tstruct drm_gpusvm_notifier *notifier;\ndrivers/gpu/drm/drm_gpusvm.c-601-\n--\ndrivers/gpu/drm/drm_gpusvm.c-620-/**\ndrivers/gpu/drm/drm_gpusvm.c:621: * drm_gpusvm_notifier_free() - Free GPU SVM notifier\ndrivers/gpu/drm/drm_gpusvm.c-622- * @gpusvm: Pointer to the GPU SVM structure\n--\ndrivers/gpu/drm/drm_gpusvm.c-626- */\ndrivers/gpu/drm/drm_gpusvm.c:627:static void drm_gpusvm_notifier_free(struct drm_gpusvm *gpusvm,\ndrivers/gpu/drm/drm_gpusvm.c:628:\t\t\t\t     struct drm_gpusvm_notifier *notifier)\ndrivers/gpu/drm/drm_gpusvm.c-629-{\n--\ndrivers/gpu/drm/drm_gpusvm.c-638-/**\ndrivers/gpu/drm/drm_gpusvm.c:639: * to_drm_gpusvm_range() - retrieve the container struct for a given rbtree node\ndrivers/gpu/drm/drm_gpusvm.c:640: * @node: a pointer to the rbtree node embedded within a drm_gpusvm_range struct\ndrivers/gpu/drm/drm_gpusvm.c-641- *\ndrivers/gpu/drm/drm_gpusvm.c:642: * Return: A pointer to the containing drm_gpusvm_range structure.\ndrivers/gpu/drm/drm_gpusvm.c-643- */\ndrivers/gpu/drm/drm_gpusvm.c:644:static struct drm_gpusvm_range *to_drm_gpusvm_range(struct rb_node *node)\ndrivers/gpu/drm/drm_gpusvm.c-645-{\ndrivers/gpu/drm/drm_gpusvm.c:646:\treturn container_of(node, struct drm_gpusvm_range, itree.rb);\ndrivers/gpu/drm/drm_gpusvm.c-647-}\n--\ndrivers/gpu/drm/drm_gpusvm.c-649-/**\ndrivers/gpu/drm/drm_gpusvm.c:650: * drm_gpusvm_range_insert() - Insert GPU SVM range\ndrivers/gpu/drm/drm_gpusvm.c-651- * @notifier: Pointer to the GPU SVM notifier structure\n--\ndrivers/gpu/drm/drm_gpusvm.c-655- */\ndrivers/gpu/drm/drm_gpusvm.c:656:static void drm_gpusvm_range_insert(struct drm_gpusvm_notifier *notifier,\ndrivers/gpu/drm/drm_gpusvm.c:657:\t\t\t\t    struct drm_gpusvm_range *range)\ndrivers/gpu/drm/drm_gpusvm.c-658-{\n--\ndrivers/gpu/drm/drm_gpusvm.c-661-\ndrivers/gpu/drm/drm_gpusvm.c:662:\tdrm_gpusvm_notifier_lock(notifier-\u003egpusvm);\ndrivers/gpu/drm/drm_gpusvm.c-663-\tinterval_tree_insert(\u0026range-\u003eitree, \u0026notifier-\u003eroot);\n--\ndrivers/gpu/drm/drm_gpusvm.c-666-\tif (node)\ndrivers/gpu/drm/drm_gpusvm.c:667:\t\thead = \u0026(to_drm_gpusvm_range(node))-\u003eentry;\ndrivers/gpu/drm/drm_gpusvm.c-668-\telse\n--\ndrivers/gpu/drm/drm_gpusvm.c-671-\tlist_add(\u0026range-\u003eentry, head);\ndrivers/gpu/drm/drm_gpusvm.c:672:\tdrm_gpusvm_notifier_unlock(notifier-\u003egpusvm);\ndrivers/gpu/drm/drm_gpusvm.c-673-}\n--\ndrivers/gpu/drm/drm_gpusvm.c-675-/**\ndrivers/gpu/drm/drm_gpusvm.c:676: * __drm_gpusvm_range_remove() - Remove GPU SVM range\ndrivers/gpu/drm/drm_gpusvm.c-677- * @notifier: Pointer to the GPU SVM notifier structure\n--\ndrivers/gpu/drm/drm_gpusvm.c-681- */\ndrivers/gpu/drm/drm_gpusvm.c:682:static void __drm_gpusvm_range_remove(struct drm_gpusvm_notifier *notifier,\ndrivers/gpu/drm/drm_gpusvm.c:683:\t\t\t\t      struct drm_gpusvm_range *range)\ndrivers/gpu/drm/drm_gpusvm.c-684-{\n--\ndrivers/gpu/drm/drm_gpusvm.c-689-/**\ndrivers/gpu/drm/drm_gpusvm.c:690: * drm_gpusvm_range_alloc() - Allocate GPU SVM range\ndrivers/gpu/drm/drm_gpusvm.c-691- * @gpusvm: Pointer to the GPU SVM structure\n--\ndrivers/gpu/drm/drm_gpusvm.c-700- */\ndrivers/gpu/drm/drm_gpusvm.c:701:static struct drm_gpusvm_range *\ndrivers/gpu/drm/drm_gpusvm.c:702:drm_gpusvm_range_alloc(struct drm_gpusvm *gpusvm,\ndrivers/gpu/drm/drm_gpusvm.c:703:\t\t       struct drm_gpusvm_notifier *notifier,\ndrivers/gpu/drm/drm_gpusvm.c-704-\t\t       unsigned long fault_addr, unsigned long chunk_size,\n--\ndrivers/gpu/drm/drm_gpusvm.c-706-{\ndrivers/gpu/drm/drm_gpusvm.c:707:\tstruct drm_gpusvm_range *range;\ndrivers/gpu/drm/drm_gpusvm.c-708-\n--\ndrivers/gpu/drm/drm_gpusvm.c-728-/**\ndrivers/gpu/drm/drm_gpusvm.c:729: * drm_gpusvm_hmm_pfn_to_order() - Get the largest CPU mapping order.\ndrivers/gpu/drm/drm_gpusvm.c-730- * @hmm_pfn: The current hmm_pfn.\n--\ndrivers/gpu/drm/drm_gpusvm.c-741- */\ndrivers/gpu/drm/drm_gpusvm.c:742:static unsigned int drm_gpusvm_hmm_pfn_to_order(unsigned long hmm_pfn,\ndrivers/gpu/drm/drm_gpusvm.c-743-\t\t\t\t\t\tunsigned long hmm_pfn_index,\n--\ndrivers/gpu/drm/drm_gpusvm.c-757-/**\ndrivers/gpu/drm/drm_gpusvm.c:758: * drm_gpusvm_check_pages() - Check pages\ndrivers/gpu/drm/drm_gpusvm.c-759- * @gpusvm: Pointer to the GPU SVM structure\n--\ndrivers/gpu/drm/drm_gpusvm.c-769- */\ndrivers/gpu/drm/drm_gpusvm.c:770:static bool drm_gpusvm_check_pages(struct drm_gpusvm *gpusvm,\ndrivers/gpu/drm/drm_gpusvm.c:771:\t\t\t\t   struct drm_gpusvm_notifier *notifier,\ndrivers/gpu/drm/drm_gpusvm.c-772-\t\t\t\t   unsigned long start, unsigned long end,\n--\ndrivers/gpu/drm/drm_gpusvm.c-816-\t\t}\ndrivers/gpu/drm/drm_gpusvm.c:817:\t\ti += 0x1 \u003c\u003c drm_gpusvm_hmm_pfn_to_order(pfns[i], i, npages);\ndrivers/gpu/drm/drm_gpusvm.c-818-\t}\n--\ndrivers/gpu/drm/drm_gpusvm.c-825-/**\ndrivers/gpu/drm/drm_gpusvm.c:826: * drm_gpusvm_scan_mm() - Check the migration state of a drm_gpusvm_range\ndrivers/gpu/drm/drm_gpusvm.c:827: * @range: Pointer to the struct drm_gpusvm_range to check.\ndrivers/gpu/drm/drm_gpusvm.c-828- * @dev_private_owner: The struct dev_private_owner to use to determine\n--\ndrivers/gpu/drm/drm_gpusvm.c-838- *\ndrivers/gpu/drm/drm_gpusvm.c:839: * Return: See \u0026enum drm_gpusvm_scan_result.\ndrivers/gpu/drm/drm_gpusvm.c-840- */\ndrivers/gpu/drm/drm_gpusvm.c:841:enum drm_gpusvm_scan_result drm_gpusvm_scan_mm(struct drm_gpusvm_range *range,\ndrivers/gpu/drm/drm_gpusvm.c-842-\t\t\t\t\t       void *dev_private_owner,\n--\ndrivers/gpu/drm/drm_gpusvm.c-845-\tstruct mmu_interval_notifier *notifier = \u0026range-\u003enotifier-\u003enotifier;\ndrivers/gpu/drm/drm_gpusvm.c:846:\tunsigned long start = drm_gpusvm_range_start(range);\ndrivers/gpu/drm/drm_gpusvm.c:847:\tunsigned long end = drm_gpusvm_range_end(range);\ndrivers/gpu/drm/drm_gpusvm.c-848-\tstruct hmm_range hmm_range = {\n--\ndrivers/gpu/drm/drm_gpusvm.c-855-\tunsigned long timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);\ndrivers/gpu/drm/drm_gpusvm.c:856:\tenum drm_gpusvm_scan_result state = DRM_GPUSVM_SCAN_UNPOPULATED, new_state;\ndrivers/gpu/drm/drm_gpusvm.c-857-\tunsigned long *pfns;\n--\ndrivers/gpu/drm/drm_gpusvm.c-872-\ndrivers/gpu/drm/drm_gpusvm.c:873:\tdrm_gpusvm_notifier_lock(range-\u003egpusvm);\ndrivers/gpu/drm/drm_gpusvm.c-874-\tif (mmu_interval_read_retry(notifier, hmm_range.notifier_seq)) {\ndrivers/gpu/drm/drm_gpusvm.c:875:\t\tdrm_gpusvm_notifier_unlock(range-\u003egpusvm);\ndrivers/gpu/drm/drm_gpusvm.c-876-\t\tgoto retry;\n--\ndrivers/gpu/drm/drm_gpusvm.c-918-\ndrivers/gpu/drm/drm_gpusvm.c:919:\t\ti += 1ul \u003c\u003c drm_gpusvm_hmm_pfn_to_order(pfns[i], i, npages);\ndrivers/gpu/drm/drm_gpusvm.c-920-\t}\ndrivers/gpu/drm/drm_gpusvm.c-921-\ndrivers/gpu/drm/drm_gpusvm.c:922:\tdrm_gpusvm_notifier_unlock(range-\u003egpusvm);\ndrivers/gpu/drm/drm_gpusvm.c-923-\n--\ndrivers/gpu/drm/drm_gpusvm.c-927-}\ndrivers/gpu/drm/drm_gpusvm.c:928:EXPORT_SYMBOL(drm_gpusvm_scan_mm);\ndrivers/gpu/drm/drm_gpusvm.c-929-\ndrivers/gpu/drm/drm_gpusvm.c-930-/**\ndrivers/gpu/drm/drm_gpusvm.c:931: * drm_gpusvm_range_chunk_size() - Determine chunk size for GPU SVM range\ndrivers/gpu/drm/drm_gpusvm.c-932- * @gpusvm: Pointer to the GPU SVM structure\n--\ndrivers/gpu/drm/drm_gpusvm.c=947=static unsigned long\ndrivers/gpu/drm/drm_gpusvm.c:948:drm_gpusvm_range_chunk_size(struct drm_gpusvm *gpusvm,\ndrivers/gpu/drm/drm_gpusvm.c:949:\t\t\t    struct drm_gpusvm_notifier *notifier,\ndrivers/gpu/drm/drm_gpusvm.c-950-\t\t\t    struct vm_area_struct *vas,\n--\ndrivers/gpu/drm/drm_gpusvm.c-965-\t\tif (start \u003e= vas-\u003evm_start \u0026\u0026 end \u003c= vas-\u003evm_end \u0026\u0026\ndrivers/gpu/drm/drm_gpusvm.c:966:\t\t    start \u003e= drm_gpusvm_notifier_start(notifier) \u0026\u0026\ndrivers/gpu/drm/drm_gpusvm.c:967:\t\t    end \u003c= drm_gpusvm_notifier_end(notifier) \u0026\u0026\ndrivers/gpu/drm/drm_gpusvm.c-968-\t\t    start \u003e= gpuva_start \u0026\u0026 end \u003c= gpuva_end)\n--\ndrivers/gpu/drm/drm_gpusvm.c-979-\tif (end - start != SZ_4K) {\ndrivers/gpu/drm/drm_gpusvm.c:980:\t\tstruct drm_gpusvm_range *range;\ndrivers/gpu/drm/drm_gpusvm.c-981-\ndrivers/gpu/drm/drm_gpusvm.c:982:\t\trange = drm_gpusvm_range_find(notifier, start, end);\ndrivers/gpu/drm/drm_gpusvm.c-983-\t\tif (range) {\n--\ndrivers/gpu/drm/drm_gpusvm.c-994-\t\t * drm_pagemap_migrate_to_devmem with 'migrate.cpages != npages'\ndrivers/gpu/drm/drm_gpusvm.c:995:\t\t * and then upon drm_gpusvm_get_pages device pages from\ndrivers/gpu/drm/drm_gpusvm.c-996-\t\t * other processes are collected + faulted in which creates all\n--\n\n"
}

gemini-3.1-pro-preview

null

null

							input: 43477
							output: 35
							thoughts: 88
						

Okay, let me think this through.

**Investigating `drm_gpusvm` Testing**

Right, `drm_gpusvm`... that's a helper library, isn't it? I need to figure out if it has any associated testing.  My initial reaction is to check for KUnit tests. The build output would usually indicate this. Hmm, no, I don't see anything explicitly mentioning "test" or "kunit" in the build output. Okay, that's not conclusive, I need to dig deeper. So, the question is, does `drm_gpusvm` actually have *any* selftests or KUnit tests? Time to examine the source code itself. I'll need to go directly to `drivers/gpu/drm/drm_gpusvm.c` and search the code for any mentions of "kunit" or "test". That should give me a definitive answer.

no matches

{
  "Expression": "kunit",
  "PathPrefix": "drivers/gpu/drm/drm_gpusvm.c"
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

null

null

							input: 43812
							output: 35
							thoughts: 258
						

**Analyzing the Impact of This Patch**

Okay, so this patch isn't touching any code that's actually tested by kunit, which is a key starting point. I looked at `drm_gpusvm`, `aie2_ctx.c`, and `nouveau_svm.c`, and none of them are covered. This immediately raises a flag: is this purely a change to unreachable code in virtualized environments, like GCE or QEMU? That's what it looks like, initially.

But wait, I need to be precise here. Is `drm_gpusvm` *potentially* reachable through the `xe` driver? Syzkaller doesn't have that specific Intel Xe hardware, so I can't immediately rule it out. And what about `nouveau` and `amdxdna`? Syzkaller's hardware limitations are definitely a factor.

Now, I almost missed something – what about `lib/test_hmm.c`? Ah, no, the patch doesn't touch that. Good. However, wait, this patch *does* modify usage of `hmm_range_fault_unlocked_timeout` in those files I mentioned earlier: `aie2_ctx.c`, `drm_gpusvm.c`, and `nouveau_svm.c`.

Okay, does it change `hmm_range_fault_unlocked_timeout` itself? I don't see any modifications to `mm/hmm.c` in the diff, so that's a negative. But I need to be absolutely certain... let me double-check this diff again. Making sure I have all the details.

{
  "Expression": "hmm_range_fault_unlocked_timeout",
  "PathPrefix": "mm/hmm.c"
}

{
  "Output": "mm/hmm.c=689=static int hmm_range_fault_locked(struct hmm_range *range, bool *locked)\n--\nmm/hmm.c-753- * The mmap lock must be held by the caller and will remain held on return.\nmm/hmm.c:754: * New users should prefer hmm_range_fault_unlocked_timeout() unless they\nmm/hmm.c-755- * specifically need to keep the mmap lock held across the call. This helper\n--\nmm/hmm.c=762=EXPORT_SYMBOL(hmm_range_fault);\n--\nmm/hmm.c-764-/**\nmm/hmm.c:765: * hmm_range_fault_unlocked_timeout - fault in a range with a retry timeout\nmm/hmm.c-766- * @range:\targument structure\n--\nmm/hmm.c-783- */\nmm/hmm.c:784:int hmm_range_fault_unlocked_timeout(struct hmm_range *range,\nmm/hmm.c-785-\t\t\t\t     unsigned long timeout)\n--\nmm/hmm.c-824-}\nmm/hmm.c:825:EXPORT_SYMBOL(hmm_range_fault_unlocked_timeout);\nmm/hmm.c-826-\n"
}

gemini-3.1-pro-preview

null

null

							input: 44784
							output: 20
							thoughts: 337
						

**Analyzing the Code Modification**

Okay, so the user's provided a diff, and my initial thought is, "Alright, let's see what's changed." I immediately scan the file paths: `Documentation/mm/hmm.rst`, `drivers/accel/amdxdna/aie2_ctx.c`, `drivers/gpu/drm/drm_gpusvm.c`, and `drivers/gpu/drm/nouveau/nouveau_svm.c`.

My gut reaction is that this probably won't be reachable via syzkaller as is. Based on the file paths, my memory kicks in. I know those paths require specific hardware: AMD XDNA, Intel Xe, and NVIDIA GPUs. These are not typically present, nor emulated, in standard virtualized environments like GCE or QEMU, which are the syzkaller go-to's.

But wait a minute... *drm_gpusvm.c*...that file name is poking at something in my mind. Could that one be reachable somehow with a mock driver? It's worth a quick double-check. Okay, focusing back in, let's see. Let me quickly jog my memory and see how that is selected. Nope, it looks like `drm_gpusvm` is only selected by `DRM_XE` and `DRM_XE_GPUSVM`. So that's the end of that thought.

Alright, so the chances of this being directly testable seem slim. Let's dig deeper. Maybe it is used by something else I am not thinking of.

{
  "Expression": "select DRM_GPUSVM"
}

{
  "Output": "drivers/gpu/drm/xe/Kconfig=2=config DRM_XE\n--\ndrivers/gpu/drm/xe/Kconfig-41-\tselect DRM_EXEC\ndrivers/gpu/drm/xe/Kconfig:42:\tselect DRM_GPUSVM if !UML\ndrivers/gpu/drm/xe/Kconfig-43-\tselect DRM_GPUVM\n--\ndrivers/gpu/drm/xe/Kconfig=79=config DRM_XE_GPUSVM\n--\ndrivers/gpu/drm/xe/Kconfig-85-\tselect DEVICE_PRIVATE\ndrivers/gpu/drm/xe/Kconfig:86:\tselect DRM_GPUSVM\ndrivers/gpu/drm/xe/Kconfig-87-\thelp\n"
}

gemini-3.1-pro-preview

null

null

							input: 45664
							output: 33
							thoughts: 393
						

**WorthFuzzing=false: Unreachable Code Paths in Virtualized Environments**

Okay, so let's break this down. It looks like the patch I'm reviewing modifies how `hmm_range_fault_unlocked_timeout` is used, and it does so within three specific GPU drivers: `amdxdna`, `drm_gpusvm.c`, and `nouveau`. A quick look at the code confirms that `drm_gpusvm.c` is exclusively used by the `xe` driver. The crucial point is that `xe`, `amdxdna`, and `nouveau` are all hardware-specific drivers. They are designed to interface with particular GPUs—AMD XDNA, Intel Xe, and NVIDIA GPUs, respectively. These drivers are not reachable in virtualized environments like GCE or QEMU without hardware passthrough.

I need to confirm if `nouveau` can even be fuzzed, given Syzkaller's current configuration. I know Syzkaller doesn't have NVIDIA GPUs in its virtual machines. I'm pretty certain that the `nouveau` driver can't be initialized without the hardware. It's a PCI driver and binds to NVIDIA PCI devices. Without the specific hardware, the driver's `probe` function won't be called, and thus, its ioctls won't be registered. The same logic applies to `amdxdna` and `xe`.

Given this, the changes introduced by this patch are, in essence, dead code in our current fuzzing setup. They're modifying code paths that are inherently unreachable within the virtualized environments we're using. I need to make sure I'm correct about `drm_gpusvm.c` and its relation to `vkms` and `vgem` before I'm 100% sure. 

Therefore, I need to flag this as `WorthFuzzing=false` and provide the reasoning: the patch modifies code within hardware-specific drivers (`amdxdna`, `xe` via `drm_gpusvm.c`, and `nouveau`). These drivers require physical hardware or hardware emulation which we don't have available in GCE/QEMU, making the modified code impossible to execute.

no matches

{
  "Expression": "drm_gpusvm",
  "PathPrefix": "drivers/gpu/drm/vkms"
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

null

null

							input: 46578
							output: 33
							thoughts: 0
						

no matches

{
  "Expression": "drm_gpusvm",
  "PathPrefix": "drivers/gpu/drm/vgem"
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

null

null

							input: 46625
							output: 32
							thoughts: 24
						

Okay, here's my summary, presented as a stream of thought:

**Confirming PCI Driver Status**

Right, so I'm seeing this thing, and the key observation is that it's *not* being utilized by the target group. That's the core of the issue.

Now, I need to get a firm grasp on the technical aspects before I can determine if this is a driver issue, a config issue, or some other problem. Let me quickly confirm that `amdxdna` is indeed functioning as a PCI driver. This is fundamental for me to proceed. If it isn't, then everything changes.

{
  "Expression": "pci_driver",
  "PathPrefix": "drivers/accel/amdxdna"
}

{
  "Output": "drivers/accel/amdxdna/amdxdna_pci_drv.c=475=static int amdxdna_sriov_configure(struct pci_dev *pdev, int num_vfs)\n--\ndrivers/accel/amdxdna/amdxdna_pci_drv.c-485-\ndrivers/accel/amdxdna/amdxdna_pci_drv.c:486:static struct pci_driver amdxdna_pci_driver = {\ndrivers/accel/amdxdna/amdxdna_pci_drv.c-487-\t.name = KBUILD_MODNAME,\n--\ndrivers/accel/amdxdna/amdxdna_pci_drv.c-494-\ndrivers/accel/amdxdna/amdxdna_pci_drv.c:495:module_pci_driver(amdxdna_pci_driver);\ndrivers/accel/amdxdna/amdxdna_pci_drv.c-496-\n"
}

gemini-3.1-pro-preview

null

null

							input: 47074
							output: 31
							thoughts: 21
						

Okay, here's my summary, in the first person, as requested:

**PCI Driver Verification - Quick Thoughts**

Alright, yep, that looks like a PCI driver, no question about it. Now, just a quick sanity check, I want to confirm that `xe` is *definitely* acting as a PCI driver. It's always good practice to double-check these assumptions before moving forward. I'll just run a quick diagnostic, nothing major, just to be absolutely certain of the initial assessment.

{
  "Expression": "pci_driver",
  "PathPrefix": "drivers/gpu/drm/xe"
}

{
  "Output": "drivers/gpu/drm/xe/tests/xe_pci.c=405=const void *xe_pci_live_device_gen_param(struct kunit *test, const void *prev, char *desc)\n--\ndrivers/gpu/drm/xe/tests/xe_pci.c-410-\ndrivers/gpu/drm/xe/tests/xe_pci.c:411:\tnext = driver_find_next_device(\u0026xe_pci_driver.driver, dev);\ndrivers/gpu/drm/xe/tests/xe_pci.c-412-\tif (dev)\n--\ndrivers/gpu/drm/xe/xe_configfs.c=1006=static const struct xe_device_desc *xe_match_desc(struct pci_dev *pdev)\n--\ndrivers/gpu/drm/xe/xe_configfs.c-1008-\tstruct device_driver *driver = driver_find(\"xe\", \u0026pci_bus_type);\ndrivers/gpu/drm/xe/xe_configfs.c:1009:\tstruct pci_driver *drv = to_pci_driver(driver);\ndrivers/gpu/drm/xe/xe_configfs.c-1010-\tconst struct pci_device_id *ids = drv ? drv-\u003eid_table : NULL;\n--\ndrivers/gpu/drm/xe/xe_module.c=96=static const struct init_funcs init_funcs[] = {\n--\ndrivers/gpu/drm/xe/xe_module.c-112-\t{\ndrivers/gpu/drm/xe/xe_module.c:113:\t\t.init = xe_register_pci_driver,\ndrivers/gpu/drm/xe/xe_module.c:114:\t\t.exit = xe_unregister_pci_driver,\ndrivers/gpu/drm/xe/xe_module.c-115-\t},\n--\ndrivers/gpu/drm/xe/xe_pci.c=1424=static const struct dev_pm_ops xe_pm_ops = {\n--\ndrivers/gpu/drm/xe/xe_pci.c-1429-\ndrivers/gpu/drm/xe/xe_pci.c:1430:static struct pci_driver xe_pci_driver = {\ndrivers/gpu/drm/xe/xe_pci.c-1431-\t.name = DRIVER_NAME,\n--\ndrivers/gpu/drm/xe/xe_pci.c=1449=struct xe_device *xe_pci_to_pf_device(struct pci_dev *pdev)\n--\ndrivers/gpu/drm/xe/xe_pci.c-1452-\ndrivers/gpu/drm/xe/xe_pci.c:1453:\tdrm = pci_iov_get_pf_drvdata(pdev, \u0026xe_pci_driver);\ndrivers/gpu/drm/xe/xe_pci.c-1454-\tif (IS_ERR(drm))\n--\ndrivers/gpu/drm/xe/xe_pci.c-1459-\ndrivers/gpu/drm/xe/xe_pci.c:1460:int xe_register_pci_driver(void)\ndrivers/gpu/drm/xe/xe_pci.c-1461-{\ndrivers/gpu/drm/xe/xe_pci.c:1462:\treturn pci_register_driver(\u0026xe_pci_driver);\ndrivers/gpu/drm/xe/xe_pci.c-1463-}\ndrivers/gpu/drm/xe/xe_pci.c-1464-\ndrivers/gpu/drm/xe/xe_pci.c:1465:void xe_unregister_pci_driver(void)\ndrivers/gpu/drm/xe/xe_pci.c-1466-{\ndrivers/gpu/drm/xe/xe_pci.c:1467:\tpci_unregister_driver(\u0026xe_pci_driver);\ndrivers/gpu/drm/xe/xe_pci.c-1468-}\n--\ndrivers/gpu/drm/xe/xe_pci.h=9=struct pci_dev;\ndrivers/gpu/drm/xe/xe_pci.h-10-\ndrivers/gpu/drm/xe/xe_pci.h:11:int xe_register_pci_driver(void);\ndrivers/gpu/drm/xe/xe_pci.h:12:void xe_unregister_pci_driver(void);\ndrivers/gpu/drm/xe/xe_pci.h-13-struct xe_device *xe_pci_to_pf_device(struct pci_dev *pdev);\n--\ndrivers/gpu/drm/xe/xe_pci_sriov.c=176=static int pf_disable_vfs(struct xe_device *xe)\n--\ndrivers/gpu/drm/xe/xe_pci_sriov.c-213- *\ndrivers/gpu/drm/xe/xe_pci_sriov.c:214: * This is the Xe implementation of struct pci_driver.sriov_configure callback.\ndrivers/gpu/drm/xe/xe_pci_sriov.c-215- *\n"
}

gemini-3.1-pro-preview

null

null

							input: 48540
							output: 32
							thoughts: 22
						

Okay, here's my take on those thoughts, tailored for an expert audience:

**Confirming PCI Driver Identity**

Right, so we're dealing with a PCI driver, that's clear enough. Now, I want to quickly solidify that this *nouveau* driver is indeed the one we're looking at. Gotta be certain before I go deeper down that rabbit hole. I know the basics, but I need to make sure I have all the pieces of the puzzle before I start trying to put them together. Let me just confirm that the module name `nouveau` corresponds with a PCI device driver, just to be absolutely sure. Gotta be thorough.

{
  "Expression": "pci_driver",
  "PathPrefix": "drivers/gpu/drm/nouveau"
}

{
  "Output": "drivers/gpu/drm/nouveau/nouveau_drm.c=1425=static const struct dev_pm_ops nouveau_pm_ops = {\n--\ndrivers/gpu/drm/nouveau/nouveau_drm.c-1436-\ndrivers/gpu/drm/nouveau/nouveau_drm.c:1437:static struct pci_driver\ndrivers/gpu/drm/nouveau/nouveau_drm.c:1438:nouveau_drm_pci_driver = {\ndrivers/gpu/drm/nouveau/nouveau_drm.c-1439-\t.name = \"nouveau\",\n--\ndrivers/gpu/drm/nouveau/nouveau_drm.c=1480=nouveau_drm_init(void)\n--\ndrivers/gpu/drm/nouveau/nouveau_drm.c-1506-#ifdef CONFIG_PCI\ndrivers/gpu/drm/nouveau/nouveau_drm.c:1507:\tret = pci_register_driver(\u0026nouveau_drm_pci_driver);\ndrivers/gpu/drm/nouveau/nouveau_drm.c-1508-\tif (ret) {\n--\ndrivers/gpu/drm/nouveau/nouveau_drm.c=1518=nouveau_drm_exit(void)\n--\ndrivers/gpu/drm/nouveau/nouveau_drm.c-1523-#ifdef CONFIG_PCI\ndrivers/gpu/drm/nouveau/nouveau_drm.c:1524:\tpci_unregister_driver(\u0026nouveau_drm_pci_driver);\ndrivers/gpu/drm/nouveau/nouveau_drm.c-1525-#endif\n"
}

gemini-3.1-pro-preview

null

null

							input: 49151
							output: 170
							thoughts: 64
						

Okay, here's my take on those thoughts, framed as my own reasoning:

**Analyzing the Patch and Its Impact**

Alright, yep, that confirms it – this is definitely a PCI driver we're dealing with. And looking at the context, it's pretty clear where the problem lies. The patch touches three drivers, and they are *all* hardware-specific PCI drivers. What that means is they're coded to interact directly with the physical hardware components on a PCI bus. They're not generic, and crucially, they need that *specific* hardware to function.

Now, considering the environment we're working with, syzkaller, it all falls into place. Syzkaller's strength is its fuzzing capabilities in a virtualized setting, which is perfect for isolating bugs. But because these drivers require *real* physical PCI hardware, and there are no dummy or virtual devices set up to mimic that hardware within syzkaller's virtual environment, the code paths touched by the patch are simply unreachable. We're effectively dealing with dead code in this specific context.

Therefore, I'm ready to formulate my response.

{
  "EnableConfigs": [],
  "FocusSymbols": [],
  "Reasoning": "The patch modifies the usage of `hmm_range_fault_unlocked_timeout` in three hardware-specific drivers: AMD XDNA (`drivers/accel/amdxdna`), Intel Xe (`drivers/gpu/drm/drm_gpusvm.c`, which is only used by `xe`), and Nouveau (`drivers/gpu/drm/nouveau`). These drivers require specific physical hardware (AMD XDNA NPU, Intel Xe GPU, NVIDIA GPU) to initialize and expose their interfaces. Since syzkaller operates in virtualized environments (GCE/QEMU) without this specific hardware or software emulation for them, these code paths are impossible to reach and fuzz.",
  "WorthFuzzing": false
}

{
  "EnableConfigs": null,
  "FocusSymbols": [],
  "Reasoning": "The patch modifies the usage of `hmm_range_fault_unlocked_timeout` in three hardware-specific drivers: AMD XDNA (`drivers/accel/amdxdna`), Intel Xe (`drivers/gpu/drm/drm_gpusvm.c`, which is only used by `xe`), and Nouveau (`drivers/gpu/drm/nouveau`). These drivers require specific physical hardware (AMD XDNA NPU, Intel Xe GPU, NVIDIA GPU) to initialize and expose their interfaces. Since syzkaller operates in virtualized environments (GCE/QEMU) without this specific hardware or software emulation for them, these code paths are impossible to reach and fuzz.",
  "WorthFuzzing": false
}