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KVM: SVM: Pass through shadow stack MSRs as appropriate

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Pass through XSAVE managed CET MSRs on SVM when KVM supports shadow
stack. These cannot be intercepted without also intercepting XSAVE which
would likely cause unacceptable performance overhead.
MSR_IA32_INT_SSP_TAB is not managed by XSAVE, so it is intercepted.

Reviewed-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: John Allen <john.allen@amd.com>
Link: https://lore.kernel.org/r/20250919223258.1604852-39-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
John Allen
2025-09-19 15:32:45 -07:00
committed by Sean Christopherson
parent c7586aa3be
commit 38c46bdbf9
1 changed files with 11 additions and 0 deletions
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arch/x86/kvm/svm/svm.c
+11
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@@ -844,6 +844,17 @@ static void svm_recalc_msr_intercepts(struct kvm_vcpu *vcpu)
svm_disable_intercept_for_msr(vcpu, MSR_IA32_MPERF, MSR_TYPE_R);
}
if (kvm_cpu_cap_has(X86_FEATURE_SHSTK)) {
bool shstk_enabled = guest_cpu_cap_has(vcpu, X86_FEATURE_SHSTK);
svm_set_intercept_for_msr(vcpu, MSR_IA32_U_CET, MSR_TYPE_RW, !shstk_enabled);
svm_set_intercept_for_msr(vcpu, MSR_IA32_S_CET, MSR_TYPE_RW, !shstk_enabled);
svm_set_intercept_for_msr(vcpu, MSR_IA32_PL0_SSP, MSR_TYPE_RW, !shstk_enabled);
svm_set_intercept_for_msr(vcpu, MSR_IA32_PL1_SSP, MSR_TYPE_RW, !shstk_enabled);
svm_set_intercept_for_msr(vcpu, MSR_IA32_PL2_SSP, MSR_TYPE_RW, !shstk_enabled);
svm_set_intercept_for_msr(vcpu, MSR_IA32_PL3_SSP, MSR_TYPE_RW, !shstk_enabled);
}
if (sev_es_guest(vcpu->kvm))
sev_es_recalc_msr_intercepts(vcpu);