From: John Allen Date: Fri, 19 Sep 2025 22:32:45 +0000 (-0700) Subject: KVM: SVM: Pass through shadow stack MSRs as appropriate X-Git-Tag: v6.18-rc1~55^2~5^2~12 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=38c46bdbf99812a07a8a7ef48718f0a03acd8a8a;p=thirdparty%2Fkernel%2Flinux.git KVM: SVM: Pass through shadow stack MSRs as appropriate 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 Signed-off-by: John Allen Link: https://lore.kernel.org/r/20250919223258.1604852-39-seanjc@google.com Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index bea8bfea74f9..1c1792f6a65c 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -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);