From d81cadbe164265337f149cf31c9462d7217c1eed Mon Sep 17 00:00:00 2001 From: Suravee Suthikulpanit Date: Mon, 4 Nov 2024 07:58:45 +0000 Subject: [PATCH] KVM: SVM: Disable AVIC on SNP-enabled system without HvInUseWrAllowed feature MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On SNP-enabled system, VMRUN marks AVIC Backing Page as in-use while the guest is running for both secure and non-secure guest. Any hypervisor write to the in-use vCPU's AVIC backing page (e.g. to inject an interrupt) will generate unexpected #PF in the host. Currently, attempt to run AVIC guest would result in the following error: BUG: unable to handle page fault for address: ff3a442e549cc270 #PF: supervisor write access in kernel mode #PF: error_code(0x80000003) - RMP violation PGD b6ee01067 P4D b6ee02067 PUD 10096d063 PMD 11c540063 PTE 80000001149cc163 SEV-SNP: PFN 0x1149cc unassigned, dumping non-zero entries in 2M PFN region: [0x114800 - 0x114a00] ... Newer AMD system is enhanced to allow hypervisor to modify the backing page for non-secure guest on SNP-enabled system. This enhancement is available when the CPUID Fn8000_001F_EAX bit 30 is set (HvInUseWrAllowed). This table describes AVIC support matrix w.r.t. SNP enablement: | Non-SNP system | SNP system ----------------------------------------------------- Non-SNP guest | AVIC Activate | AVIC Activate iff | | HvInuseWrAllowed=1 ----------------------------------------------------- SNP guest | N/A | Secure AVIC Therefore, check and disable AVIC in kvm_amd driver when the feature is not available on SNP-enabled system. See the AMD64 Architecture Programmer’s Manual (APM) Volume 2 for detail. (https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/ programmer-references/40332.pdf) Fixes: 216d106c7ff7 ("x86/sev: Add SEV-SNP host initialization support") Signed-off-by: Suravee Suthikulpanit Link: https://lore.kernel.org/r/20241104075845.7583-1-suravee.suthikulpanit@amd.com Signed-off-by: Sean Christopherson --- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/kvm/svm/avic.c | 6 ++++++ 2 files changed, 7 insertions(+) diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 17b6590748c00c..645aa360628da7 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -452,6 +452,7 @@ #define X86_FEATURE_SME_COHERENT (19*32+10) /* AMD hardware-enforced cache coherency */ #define X86_FEATURE_DEBUG_SWAP (19*32+14) /* "debug_swap" AMD SEV-ES full debug state swap support */ #define X86_FEATURE_SVSM (19*32+28) /* "svsm" SVSM present */ +#define X86_FEATURE_HV_INUSE_WR_ALLOWED (19*32+30) /* Allow Write to in-use hypervisor-owned pages */ /* AMD-defined Extended Feature 2 EAX, CPUID level 0x80000021 (EAX), word 20 */ #define X86_FEATURE_NO_NESTED_DATA_BP (20*32+ 0) /* No Nested Data Breakpoints */ diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c index 4b74ea91f4e6bb..65fd245a9953ce 100644 --- a/arch/x86/kvm/svm/avic.c +++ b/arch/x86/kvm/svm/avic.c @@ -1199,6 +1199,12 @@ bool avic_hardware_setup(void) return false; } + if (cc_platform_has(CC_ATTR_HOST_SEV_SNP) && + !boot_cpu_has(X86_FEATURE_HV_INUSE_WR_ALLOWED)) { + pr_warn("AVIC disabled: missing HvInUseWrAllowed on SNP-enabled system\n"); + return false; + } + if (boot_cpu_has(X86_FEATURE_AVIC)) { pr_info("AVIC enabled\n"); } else if (force_avic) {