On 14/01/21 01:36, Sean Christopherson wrote:
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. Cc: Brijesh Singh <brijesh.singh@xxxxxxx> Cc: Tom Lendacky <thomas.lendacky@xxxxxxx> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/kvm/cpuid.c | 2 ++ arch/x86/kvm/cpuid.h | 1 + 2 files changed, 3 insertions(+) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 13036cf0b912..b7618cdd06b5 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -855,6 +855,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) case 0x8000001F: if (!boot_cpu_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/cpuid.h b/arch/x86/kvm/cpuid.h index dc921d76e42e..8b6fc9bde248 100644 --- a/arch/x86/kvm/cpuid.h +++ b/arch/x86/kvm/cpuid.h @@ -63,6 +63,7 @@ static const struct cpuid_reg reverse_cpuid[] = { [CPUID_8000_0007_EBX] = {0x80000007, 0, CPUID_EBX}, [CPUID_7_EDX] = { 7, 0, CPUID_EDX}, [CPUID_7_1_EAX] = { 7, 1, CPUID_EAX}, + [CPUID_8000_001F_EAX] = {0x8000001f, 1, CPUID_EAX}, };/*
I don't understand, wouldn't this also need a kvm_cpu_cap_mask call somewhere else? As it is, it doesn't do anything.
Paolo
