FOLL_LONGTERM pinning fails for some memory types, such as file-backed guest memory. As a result, kvm_s390_adapter_map() returns -EINVAL and irqfd adapter registration fails even though interrupt delivery could still work via the existing non-atomic path. When FOLL_LONGTERM pinning fails, verify that the page is accessible using a short-term pin instead. If the short-term pin succeeds, unpin the page and add a map entry with pinned=false to preserve MAP/UNMAP symmetry. The non-atomic irqfd path already performs short-term pinning for interrupt delivery, so this restores the previous behavior for memory that cannot be pinned long-term. get_map_info() is updated to return NULL for unpinned entries so that the atomic irqfd fast path falls back to the non-atomic path. kvm_s390_adapter_unmap() and kvm_s390_unmap_all_adapters() skip dirty marking and unpin for unpinned entries. Update Documentation/virt/kvm/devices/s390_flic.rst to reflect the new MAP/UNMAP behavior. Fixes: c9a568838086 ("KVM: s390: Add map/unmap ioctl and clean mappings post-guest") Signed-off-by: Jaehoon Kim Reviewed-by: Douglas Freimuth Reviewed-by: Matthew Rosato --- Documentation/virt/kvm/devices/s390_flic.rst | 15 +++++- arch/s390/include/asm/kvm_host.h | 5 ++ arch/s390/kvm/interrupt.c | 56 +++++++++++++++----- 3 files changed, 60 insertions(+), 16 deletions(-) diff --git a/Documentation/virt/kvm/devices/s390_flic.rst b/Documentation/virt/kvm/devices/s390_flic.rst index b784f8016748..983c858b444a 100644 --- a/Documentation/virt/kvm/devices/s390_flic.rst +++ b/Documentation/virt/kvm/devices/s390_flic.rst @@ -112,9 +112,20 @@ Groups: mask or unmask the adapter, as specified in mask KVM_S390_IO_ADAPTER_MAP - This is now a no-op. The mapping is purely done by the irq route. + Map an adapter indicator or summary page for long-term pinning so that + interrupt injection can be performed in atomic context. If long-term + pinning is not possible (e.g. file-backed memory), the page is verified + via a short-term pin and the ioctl returns success; interrupt injection + will use the non-atomic irqfd path with short-term pinning on each + interrupt. In Secure Execution mode this is a no-op and the ioctl + returns success. + KVM_S390_IO_ADAPTER_UNMAP - This is now a no-op. The mapping is purely done by the irq route. + Unmap a previously mapped adapter indicator or summary page and release + the long-term pin. If the page was not long-term pinned (e.g. file-backed + memory), the map entry is removed and success is returned; if no prior + map entry exists, -ENOENT is returned. In Secure Execution mode this is + a no-op and the ioctl returns success. KVM_DEV_FLIC_AISM modify the adapter-interruption-suppression mode for a given isc if the diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h index eaa34c5bd3c1..c172f9b212d1 100644 --- a/arch/s390/include/asm/kvm_host.h +++ b/arch/s390/include/asm/kvm_host.h @@ -476,6 +476,11 @@ struct s390_map_info { __u64 guest_addr; __u64 addr; struct page *page; + /* + * True if the page is long-term pinned. False if long-term pinning + * failed and this entry exists only to preserve MAP/UNMAP symmetry. + */ + bool pinned; }; struct s390_io_adapter { diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c index 9e3e6b0d72ad..7514d9e2403c 100644 --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -2520,8 +2520,22 @@ static int kvm_s390_adapter_map(struct kvm *kvm, unsigned int id, __u64 addr) map->addr = host_addr; map->page = pin_map_page(kvm, host_addr, FOLL_LONGTERM); if (!map->page) { - ret = -EINVAL; - goto out; + /* + * Long-term pinning may fail for memory types such as file-backed + * memory. Verify that short-term pinning succeeds so that the + * non-atomic irqfd path can handle interrupt injection. + */ + map->page = pin_map_page(kvm, host_addr, 0); + if (!map->page) { + ret = -EINVAL; + goto out; + } + unpin_user_page(map->page); + map->page = NULL; + map->pinned = false; + /* Add an entry to preserve MAP/UNMAP symmetry. */ + } else { + map->pinned = true; } spin_lock_irqsave(&adapter->maps_lock, flags); if (adapter->nr_maps < MAX_S390_ADAPTER_MAPS) { @@ -2532,7 +2546,7 @@ static int kvm_s390_adapter_map(struct kvm *kvm, unsigned int id, __u64 addr) ret = -EINVAL; } spin_unlock_irqrestore(&adapter->maps_lock, flags); - if (ret) + if (ret && map->page) unpin_user_page(map->page); out: if (ret) @@ -2546,6 +2560,7 @@ static int kvm_s390_adapter_unmap(struct kvm *kvm, unsigned int id, __u64 addr) struct s390_map_info *map, *tmp, *map_to_free; struct page *map_page_to_put = NULL; u64 map_addr_to_mark = 0; + bool map_pinned = false; unsigned long flags; int found = 0, idx; @@ -2560,6 +2575,7 @@ static int kvm_s390_adapter_unmap(struct kvm *kvm, unsigned int id, __u64 addr) list_del(&map->list); map_page_to_put = map->page; map_addr_to_mark = map->guest_addr; + map_pinned = map->pinned; map_to_free = map; break; } @@ -2568,11 +2584,18 @@ static int kvm_s390_adapter_unmap(struct kvm *kvm, unsigned int id, __u64 addr) if (found) { kfree(map_to_free); - idx = srcu_read_lock(&kvm->srcu); - mark_page_dirty(kvm, map_addr_to_mark >> PAGE_SHIFT); - set_page_dirty_lock(map_page_to_put); - srcu_read_unlock(&kvm->srcu, idx); - unpin_user_page(map_page_to_put); + if (map_pinned) { + /* + * Only long-term pinned pages need to be marked dirty + * and released. Fallback entries exist only for + * MAP/UNMAP symmetry. + */ + idx = srcu_read_lock(&kvm->srcu); + mark_page_dirty(kvm, map_addr_to_mark >> PAGE_SHIFT); + set_page_dirty_lock(map_page_to_put); + srcu_read_unlock(&kvm->srcu, idx); + unpin_user_page(map_page_to_put); + } } return found ? 0 : -ENOENT; @@ -2598,11 +2621,13 @@ void kvm_s390_unmap_all_adapters(struct kvm *kvm) list_for_each_entry_safe(map, tmp, &local_list, list) { list_del(&map->list); - idx = srcu_read_lock(&kvm->srcu); - mark_page_dirty(kvm, map->guest_addr >> PAGE_SHIFT); - set_page_dirty_lock(map->page); - srcu_read_unlock(&kvm->srcu, idx); - unpin_user_page(map->page); + if (map->pinned) { + idx = srcu_read_lock(&kvm->srcu); + mark_page_dirty(kvm, map->guest_addr >> PAGE_SHIFT); + set_page_dirty_lock(map->page); + srcu_read_unlock(&kvm->srcu, idx); + unpin_user_page(map->page); + } kfree(map); } } @@ -2929,8 +2954,11 @@ static struct s390_map_info *get_map_info(struct s390_io_adapter *adapter, return NULL; list_for_each_entry(map, &adapter->maps, list) { - if (map->addr == addr) + if (map->addr == addr) { + if (!map->pinned) + return NULL; return map; + } } return NULL; } -- 2.43.0