From: Anil Altinay <aaltinay@google.com>
To: stable@vger.kernel.org
Cc: Jim Mattson <jmattson@google.com>,
Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, Anil Altinay <aaltinay@google.com>
Subject: [PATCH 6.18.y v2 1/6] KVM: x86: Ignore cpuid faulting in SMM
Date: Thu, 15 Oct 2026 16:03:41 +0000 [thread overview]
Message-ID: <20261015160346.181835-2-aaltinay@google.com> (raw)
In-Reply-To: <20261015160346.181835-1-aaltinay@google.com>
From: Jim Mattson <jmattson@google.com>
commit 690dc03859e7907bc995f389618c748619559477 upstream.
The Intel Virtualization Technology FlexMigration Application Note says,
"When CPUID faulting is enabled, all executions of the CPUID instruction
outside system-management mode (SMM) cause a general-protection exception
(#GP(0)) if the current privilege level (CPL) is greater than 0."
Always allow the execution of CPUID in SMM.
Fixes: db2336a80489 ("KVM: x86: virtualize cpuid faulting")
Signed-off-by: Jim Mattson <jmattson@google.com>
Link: https://patch.msgid.link/20260210234613.1383279-1-jmattson@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Anil Altinay <aaltinay@google.com>
---
arch/x86/kvm/cpuid.c | 3 ++-
arch/x86/kvm/emulate.c | 6 +++---
2 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 913ffb995279..bfa89fbe826b 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -2098,7 +2098,8 @@ int kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
{
u32 eax, ebx, ecx, edx;
- if (cpuid_fault_enabled(vcpu) && !kvm_require_cpl(vcpu, 0))
+ if (!is_smm(vcpu) && cpuid_fault_enabled(vcpu) &&
+ !kvm_require_cpl(vcpu, 0))
return 1;
eax = kvm_rax_read(vcpu);
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 9dbf3623e79e..8aa10d0e9894 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3560,10 +3560,10 @@ static int em_cpuid(struct x86_emulate_ctxt *ctxt)
u64 msr = 0;
ctxt->ops->get_msr(ctxt, MSR_MISC_FEATURES_ENABLES, &msr);
- if (msr & MSR_MISC_FEATURES_ENABLES_CPUID_FAULT &&
- ctxt->ops->cpl(ctxt)) {
+ if (!ctxt->ops->is_smm(ctxt) &&
+ (msr & MSR_MISC_FEATURES_ENABLES_CPUID_FAULT) &&
+ ctxt->ops->cpl(ctxt))
return emulate_gp(ctxt, 0);
- }
eax = reg_read(ctxt, VCPU_REGS_RAX);
ecx = reg_read(ctxt, VCPU_REGS_RCX);
--
2.56.0.385.gd3acb90ef8-goog
next prev parent reply other threads:[~2026-10-15 16:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-15 16:03 [PATCH 6.18.y v2 0/6] KVM: x86: CPUID faulting fixes and AMD CPUID faulting virtualization Anil Altinay
2026-10-15 16:03 ` Anil Altinay [this message]
2026-10-15 16:03 ` [PATCH 6.18.y v2 2/6] KVM: x86: Consolidate CPUID fault handling for emulator and interception logic Anil Altinay
2026-10-15 16:03 ` [PATCH 6.18.y v2 3/6] KVM: x86: Prioritize CPUID faulting over CPUID VM-exits in nested VMX Anil Altinay
2026-10-15 16:03 ` [PATCH 6.18.y v2 4/6] KVM: x86: Remove supports_cpuid_fault() helper Anil Altinay
2026-10-15 16:03 ` [PATCH 6.18.y v2 5/6] KVM: x86: Virtualize AMD CPUID faulting Anil Altinay
2026-10-15 16:03 ` [PATCH 6.18.y v2 6/6] KVM: selftests: Update hwcr_msr_test for CPUID faulting bit Anil Altinay
2026-10-16 1:09 ` [PATCH 6.18.y v2 0/6] KVM: x86: CPUID faulting fixes and AMD CPUID faulting virtualization Sean Christopherson
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