From: Ashish Kalra <ashish.kalra@amd.com>

The new RMPOPT instruction sets bits in a per-CPU RMPOPT table, which
indicates whether specific 1GB physical memory regions contain SEV-SNP
guest memory.

Per-CPU RMPOPT tables support at most 2 TB of addressable memory for
RMP optimizations.

Initialize the per-CPU RMPOPT table base to the starting physical
address. This enables RMP optimization for up to 2 TB of system RAM on
all CPUs.

Suggested-by: Thomas Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
---
 arch/x86/include/asm/msr-index.h |  3 +++
 arch/x86/virt/svm/sev.c          | 37 ++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index da5275d8eda6..8e7da03abd5b 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -753,6 +753,9 @@
 #define MSR_AMD64_SEG_RMP_ENABLED_BIT	0
 #define MSR_AMD64_SEG_RMP_ENABLED	BIT_ULL(MSR_AMD64_SEG_RMP_ENABLED_BIT)
 #define MSR_AMD64_RMP_SEGMENT_SHIFT(x)	(((x) & GENMASK_ULL(13, 8)) >> 8)
+#define MSR_AMD64_RMPOPT_BASE		0xc0010139
+#define MSR_AMD64_RMPOPT_ENABLE_BIT	0
+#define MSR_AMD64_RMPOPT_ENABLE		BIT_ULL(MSR_AMD64_RMPOPT_ENABLE_BIT)
 
 #define MSR_SVSM_CAA			0xc001f000
 
diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index a4f3a364fb65..405199c2f563 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -500,6 +500,41 @@ static bool __init setup_rmptable(void)
 	}
 }
 
+static void __configure_rmpopt(void *val)
+{
+	u64 rmpopt_base = ((u64)val & PUD_MASK) | MSR_AMD64_RMPOPT_ENABLE;
+
+	wrmsrq(MSR_AMD64_RMPOPT_BASE, rmpopt_base);
+}
+
+static __init void configure_and_enable_rmpopt(void)
+{
+	phys_addr_t pa_start = ALIGN_DOWN(PFN_PHYS(min_low_pfn), PUD_SIZE);
+
+	if (!cpu_feature_enabled(X86_FEATURE_RMPOPT)) {
+		pr_debug("RMPOPT not supported on this platform\n");
+		return;
+	}
+
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP)) {
+		pr_debug("RMPOPT optimizations not enabled as SNP support is not enabled\n");
+		return;
+	}
+
+	if (!(rmp_cfg & MSR_AMD64_SEG_RMP_ENABLED)) {
+		pr_info("RMPOPT optimizations not enabled, segmented RMP required\n");
+		return;
+	}
+
+	/*
+	 * Per-CPU RMPOPT tables support at most 2 TB of addressable memory for RMP optimizations.
+	 *
+	 * Set per-core RMPOPT base to min_low_pfn to enable RMP optimization for
+	 * up to 2TB of system RAM on all CPUs.
+	 */
+	on_each_cpu_mask(cpu_online_mask, __configure_rmpopt, (void *)pa_start, true);
+}
+
 /*
  * Do the necessary preparations which are verified by the firmware as
  * described in the SNP_INIT_EX firmware command description in the SNP
@@ -555,6 +590,8 @@ int __init snp_rmptable_init(void)
 skip_enable:
 	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/rmptable_init:online", __snp_enable, NULL);
 
+	configure_and_enable_rmpopt();
+
 	/*
 	 * Setting crash_kexec_post_notifiers to 'true' to ensure that SNP panic
 	 * notifier is invoked to do SNP IOMMU shutdown before kdump.
-- 
2.43.0