From fe60e8f65f79138ffdcc8a9155036cc35f6079ac Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 15 Aug 2023 13:36:44 -0700 Subject: KVM: x86: Use KVM-governed feature framework to track "XSAVES enabled" Use the governed feature framework to track if XSAVES is "enabled", i.e. if XSAVES can be used by the guest. Add a comment in the SVM code to explain the very unintuitive logic of deliberately NOT checking if XSAVES is enumerated in the guest CPUID model. No functional change intended. Reviewed-by: Yuan Yao Link: https://lore.kernel.org/r/20230815203653.519297-7-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/include/asm/kvm_host.h | 1 - arch/x86/kvm/governed_features.h | 1 + arch/x86/kvm/svm/svm.c | 17 ++++++++++++++--- arch/x86/kvm/vmx/vmx.c | 36 ++++++++++++++++++------------------ arch/x86/kvm/x86.c | 4 ++-- 5 files changed, 35 insertions(+), 24 deletions(-) (limited to 'arch') diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 007fa8bfd634..771adf2438bc 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -746,7 +746,6 @@ struct kvm_vcpu_arch { u64 smi_count; bool at_instruction_boundary; bool tpr_access_reporting; - bool xsaves_enabled; bool xfd_no_write_intercept; u64 ia32_xss; u64 microcode_version; diff --git a/arch/x86/kvm/governed_features.h b/arch/x86/kvm/governed_features.h index b29c15d5e038..b896a64e4ac3 100644 --- a/arch/x86/kvm/governed_features.h +++ b/arch/x86/kvm/governed_features.h @@ -6,6 +6,7 @@ BUILD_BUG() #define KVM_GOVERNED_X86_FEATURE(x) KVM_GOVERNED_FEATURE(X86_FEATURE_##x) KVM_GOVERNED_X86_FEATURE(GBPAGES) +KVM_GOVERNED_X86_FEATURE(XSAVES) #undef KVM_GOVERNED_X86_FEATURE #undef KVM_GOVERNED_FEATURE diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 6d8932e05753..1c6b1175016d 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4244,9 +4244,20 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) struct vcpu_svm *svm = to_svm(vcpu); struct kvm_cpuid_entry2 *best; - vcpu->arch.xsaves_enabled = guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) && - boot_cpu_has(X86_FEATURE_XSAVE) && - boot_cpu_has(X86_FEATURE_XSAVES); + /* + * SVM doesn't provide a way to disable just XSAVES in the guest, KVM + * can only disable all variants of by disallowing CR4.OSXSAVE from + * being set. As a result, if the host has XSAVE and XSAVES, and the + * guest has XSAVE enabled, the guest can execute XSAVES without + * faulting. Treat XSAVES as enabled in this case regardless of + * whether it's advertised to the guest so that KVM context switches + * XSS on VM-Enter/VM-Exit. Failure to do so would effectively give + * the guest read/write access to the host's XSS. + */ + if (boot_cpu_has(X86_FEATURE_XSAVE) && + boot_cpu_has(X86_FEATURE_XSAVES) && + guest_cpuid_has(vcpu, X86_FEATURE_XSAVE)) + kvm_governed_feature_set(vcpu, X86_FEATURE_XSAVES); /* Update nrips enabled cache */ svm->nrips_enabled = kvm_cpu_cap_has(X86_FEATURE_NRIPS) && diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index d0bba4a34824..55cd17231867 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -4543,16 +4543,19 @@ vmx_adjust_secondary_exec_control(struct vcpu_vmx *vmx, u32 *exec_control, * based on a single guest CPUID bit, with a dedicated feature bit. This also * verifies that the control is actually supported by KVM and hardware. */ -#define vmx_adjust_sec_exec_control(vmx, exec_control, name, feat_name, ctrl_name, exiting) \ -({ \ - bool __enabled; \ - \ - if (cpu_has_vmx_##name()) { \ - __enabled = guest_cpuid_has(&(vmx)->vcpu, \ - X86_FEATURE_##feat_name); \ - vmx_adjust_secondary_exec_control(vmx, exec_control, \ - SECONDARY_EXEC_##ctrl_name, __enabled, exiting); \ - } \ +#define vmx_adjust_sec_exec_control(vmx, exec_control, name, feat_name, ctrl_name, exiting) \ +({ \ + struct kvm_vcpu *__vcpu = &(vmx)->vcpu; \ + bool __enabled; \ + \ + if (cpu_has_vmx_##name()) { \ + if (kvm_is_governed_feature(X86_FEATURE_##feat_name)) \ + __enabled = guest_can_use(__vcpu, X86_FEATURE_##feat_name); \ + else \ + __enabled = guest_cpuid_has(__vcpu, X86_FEATURE_##feat_name); \ + vmx_adjust_secondary_exec_control(vmx, exec_control, SECONDARY_EXEC_##ctrl_name,\ + __enabled, exiting); \ + } \ }) /* More macro magic for ENABLE_/opt-in versus _EXITING/opt-out controls. */ @@ -4612,10 +4615,7 @@ static u32 vmx_secondary_exec_control(struct vcpu_vmx *vmx) if (!enable_pml || !atomic_read(&vcpu->kvm->nr_memslots_dirty_logging)) exec_control &= ~SECONDARY_EXEC_ENABLE_PML; - if (cpu_has_vmx_xsaves()) - vmx_adjust_secondary_exec_control(vmx, &exec_control, - SECONDARY_EXEC_ENABLE_XSAVES, - vcpu->arch.xsaves_enabled, false); + vmx_adjust_sec_exec_feature(vmx, &exec_control, xsaves, XSAVES); /* * RDPID is also gated by ENABLE_RDTSCP, turn on the control if either @@ -4634,6 +4634,7 @@ static u32 vmx_secondary_exec_control(struct vcpu_vmx *vmx) SECONDARY_EXEC_ENABLE_RDTSCP, rdpid_or_rdtscp_enabled, false); } + vmx_adjust_sec_exec_feature(vmx, &exec_control, invpcid, INVPCID); vmx_adjust_sec_exec_exiting(vmx, &exec_control, rdrand, RDRAND); @@ -7743,10 +7744,9 @@ static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) * to the guest. XSAVES depends on CR4.OSXSAVE, and CR4.OSXSAVE can be * set if and only if XSAVE is supported. */ - vcpu->arch.xsaves_enabled = kvm_cpu_cap_has(X86_FEATURE_XSAVES) && - boot_cpu_has(X86_FEATURE_XSAVE) && - guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) && - guest_cpuid_has(vcpu, X86_FEATURE_XSAVES); + if (boot_cpu_has(X86_FEATURE_XSAVE) && + guest_cpuid_has(vcpu, X86_FEATURE_XSAVE)) + kvm_governed_feature_check_and_set(vcpu, X86_FEATURE_XSAVES); vmx_setup_uret_msrs(vmx); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index c91de9897e32..7849ea0b0bf7 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1015,7 +1015,7 @@ void kvm_load_guest_xsave_state(struct kvm_vcpu *vcpu) if (vcpu->arch.xcr0 != host_xcr0) xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0); - if (vcpu->arch.xsaves_enabled && + if (guest_can_use(vcpu, X86_FEATURE_XSAVES) && vcpu->arch.ia32_xss != host_xss) wrmsrl(MSR_IA32_XSS, vcpu->arch.ia32_xss); } @@ -1046,7 +1046,7 @@ void kvm_load_host_xsave_state(struct kvm_vcpu *vcpu) if (vcpu->arch.xcr0 != host_xcr0) xsetbv(XCR_XFEATURE_ENABLED_MASK, host_xcr0); - if (vcpu->arch.xsaves_enabled && + if (guest_can_use(vcpu, X86_FEATURE_XSAVES) && vcpu->arch.ia32_xss != host_xss) wrmsrl(MSR_IA32_XSS, host_xss); } -- cgit v1.2.3