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| author | Sean Christopherson <seanjc@google.com> | 2025-06-10 15:57:06 -0700 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2025-06-20 13:05:39 -0700 |
| commit | 674ffc65035119be0ea2664684d1e8d004409ae1 (patch) | |
| tree | 89c3666df931e4f0f2e7683418eeb57a22dcf712 | |
| parent | 6b1dd26544d045f6a79e8c73572c0c0db3ef3c1a (diff) | |
| download | linux-next-674ffc65035119be0ea2664684d1e8d004409ae1.tar.gz linux-next-674ffc65035119be0ea2664684d1e8d004409ae1.zip | |
KVM: SVM: Disable interception of SPEC_CTRL iff the MSR exists for the guest
Disable interception of SPEC_CTRL when the CPU virtualizes (i.e. context
switches) SPEC_CTRL if and only if the MSR exists according to the vCPU's
CPUID model. Letting the guest access SPEC_CTRL is generally benign, but
the guest would see inconsistent behavior if KVM happened to emulate an
access to the MSR.
Fixes: d00b99c514b3 ("KVM: SVM: Add support for Virtual SPEC_CTRL")
Reported-by: Chao Gao <chao.gao@intel.com>
Link: https://lore.kernel.org/r/20250610225737.156318-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
| -rw-r--r-- | arch/x86/kvm/svm/svm.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index be8c43049f4d..9c6ec5e88141 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -1356,11 +1356,14 @@ static void init_vmcb(struct kvm_vcpu *vcpu) svm_recalc_instruction_intercepts(vcpu, svm); /* - * If the host supports V_SPEC_CTRL then disable the interception - * of MSR_IA32_SPEC_CTRL. + * If the CPU virtualizes MSR_IA32_SPEC_CTRL, i.e. KVM doesn't need to + * manually context switch the MSR, immediately configure interception + * of SPEC_CTRL, without waiting for the guest to access the MSR. */ if (boot_cpu_has(X86_FEATURE_V_SPEC_CTRL)) - set_msr_interception(vcpu, svm->msrpm, MSR_IA32_SPEC_CTRL, 1, 1); + set_msr_interception(vcpu, svm->msrpm, MSR_IA32_SPEC_CTRL, + guest_has_spec_ctrl_msr(vcpu), + guest_has_spec_ctrl_msr(vcpu)); if (kvm_vcpu_apicv_active(vcpu)) avic_init_vmcb(svm, vmcb); |