From d9db0fd6c5c9fa7c9a462a2c54d5e91455a74fca Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 21 Apr 2021 19:11:15 -0700 Subject: KVM: SEV: Mask CPUID[0x8000001F].eax according to supported features Add a reverse-CPUID entry for the memory encryption word, 0x8000001F.EAX, and use it to override the supported CPUID flags reported to userspace. Masking the reported CPUID flags avoids over-reporting KVM support, e.g. without the mask a SEV-SNP capable CPU may incorrectly advertise SNP support to userspace. Clear SEV/SEV-ES if their corresponding module parameters are disabled, and clear the memory encryption leaf completely if SEV is not fully supported in KVM. Advertise SME_COHERENT in addition to SEV and SEV-ES, as the guest can use SME_COHERENT to avoid CLFLUSH operations. Explicitly omit SME and VM_PAGE_FLUSH from the reporting. These features are used by KVM, but are not exposed to the guest, e.g. guest access to related MSRs will fault. Cc: Tom Lendacky Cc: Brijesh Singh Signed-off-by: Paolo Bonzini Co-developed-by: Sean Christopherson Signed-off-by: Sean Christopherson Message-Id: <20210422021125.3417167-6-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/cpuid.c | 8 +++++++- arch/x86/kvm/reverse_cpuid.h | 1 + arch/x86/kvm/svm/sev.c | 8 ++++++++ arch/x86/kvm/svm/svm.c | 3 +++ arch/x86/kvm/svm/svm.h | 1 + 5 files changed, 20 insertions(+), 1 deletion(-) (limited to 'arch/x86/kvm') diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 8e3033fe91c3..e9d644147bf5 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -558,6 +558,10 @@ void kvm_set_cpu_caps(void) */ kvm_cpu_cap_mask(CPUID_8000_000A_EDX, 0); + kvm_cpu_cap_mask(CPUID_8000_001F_EAX, + 0 /* SME */ | F(SEV) | 0 /* VM_PAGE_FLUSH */ | F(SEV_ES) | + F(SME_COHERENT)); + kvm_cpu_cap_mask(CPUID_C000_0001_EDX, F(XSTORE) | F(XSTORE_EN) | F(XCRYPT) | F(XCRYPT_EN) | F(ACE2) | F(ACE2_EN) | F(PHE) | F(PHE_EN) | @@ -945,8 +949,10 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) break; /* Support memory encryption cpuid if host supports it */ case 0x8000001F: - if (!boot_cpu_has(X86_FEATURE_SEV)) + if (!kvm_cpu_cap_has(X86_FEATURE_SEV)) entry->eax = entry->ebx = entry->ecx = entry->edx = 0; + else + cpuid_entry_override(entry, CPUID_8000_001F_EAX); break; /*Add support for Centaur's CPUID instruction*/ case 0xC0000000: diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h index 8e0756ddab1a..a19d473d0184 100644 --- a/arch/x86/kvm/reverse_cpuid.h +++ b/arch/x86/kvm/reverse_cpuid.h @@ -47,6 +47,7 @@ static const struct cpuid_reg reverse_cpuid[] = { [CPUID_7_EDX] = { 7, 0, CPUID_EDX}, [CPUID_7_1_EAX] = { 7, 1, CPUID_EAX}, [CPUID_12_EAX] = {0x00000012, 0, CPUID_EAX}, + [CPUID_8000_001F_EAX] = {0x8000001f, 0, CPUID_EAX}, }; /* diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index d7088a1d4de6..055aedec2f64 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -1807,6 +1807,14 @@ void sev_vm_destroy(struct kvm *kvm) sev_asid_free(sev); } +void __init sev_set_cpu_caps(void) +{ + if (!sev) + kvm_cpu_cap_clear(X86_FEATURE_SEV); + if (!sev_es) + kvm_cpu_cap_clear(X86_FEATURE_SEV_ES); +} + void __init sev_hardware_setup(void) { unsigned int eax, ebx, ecx, edx, sev_asid_count, sev_es_asid_count; diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index cbddcdb18d97..eed6f9455e1b 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -923,6 +923,9 @@ static __init void svm_set_cpu_caps(void) if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD) || boot_cpu_has(X86_FEATURE_AMD_SSBD)) kvm_cpu_cap_set(X86_FEATURE_VIRT_SSBD); + + /* CPUID 0x8000001F (SME/SEV features) */ + sev_set_cpu_caps(); } static __init int svm_hardware_setup(void) diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h index afc3166c9027..81894fd649bd 100644 --- a/arch/x86/kvm/svm/svm.h +++ b/arch/x86/kvm/svm/svm.h @@ -575,6 +575,7 @@ int svm_unregister_enc_region(struct kvm *kvm, struct kvm_enc_region *range); int svm_vm_copy_asid_from(struct kvm *kvm, unsigned int source_fd); void pre_sev_run(struct vcpu_svm *svm, int cpu); +void __init sev_set_cpu_caps(void); void __init sev_hardware_setup(void); void sev_hardware_teardown(void); void sev_free_vcpu(struct kvm_vcpu *vcpu); -- cgit v1.2.3