| Message ID | 20240405001614.924824-1-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | x86/cpufeatures: Add CPUID_LNX_5 to track recently added Linux-defined word | expand |
On 4/4/24 17:16, Sean Christopherson wrote: > Add CPUID_LNX_5 to track cpufeatures' word 21, and add the appropriate > compile-time assert in KVM to prevent direct lookups on the features in > CPUID_LNX_5. KVM uses X86_FEATURE_* flags to manage guest CPUID, and so > must translate features that are scattered by Linux from the Linux-defined > bit to the hardware-defined bit, i.e. should never try to directly access > scattered features in guest CPUID. > > Opportunistically add NR_CPUID_WORDS to enum cpuid_leafs, along with a > compile-time assert in KVM's CPUID infrastructure to ensure that future > additions update cpuid_leafs along with NCAPINTS. > > No functional change intended. > > Fixes: 7f274e609f3d ("x86/cpufeatures: Add new word for scattered features") > Cc: Sandipan Das <sandipan.das@amd.com> > Signed-off-by: Sean Christopherson <seanjc@google.com> I don't think I noticed this KVM code before, or at least how it depended on the enum. But the BUILD_BUG_ON() will surely make the ignorant among us aware _now_. Looks good: Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 42157ddcc09d..686e92d2663e 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -33,6 +33,8 @@ enum cpuid_leafs CPUID_7_EDX, CPUID_8000_001F_EAX, CPUID_8000_0021_EAX, + CPUID_LNX_5, + NR_CPUID_WORDS, }; #define X86_CAP_FMT_NUM "%d:%d" diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h index aadefcaa9561..58ac8d69c94b 100644 --- a/arch/x86/kvm/reverse_cpuid.h +++ b/arch/x86/kvm/reverse_cpuid.h @@ -102,10 +102,12 @@ static const struct cpuid_reg reverse_cpuid[] = { */ static __always_inline void reverse_cpuid_check(unsigned int x86_leaf) { + BUILD_BUG_ON(NR_CPUID_WORDS != NCAPINTS); BUILD_BUG_ON(x86_leaf == CPUID_LNX_1); BUILD_BUG_ON(x86_leaf == CPUID_LNX_2); BUILD_BUG_ON(x86_leaf == CPUID_LNX_3); BUILD_BUG_ON(x86_leaf == CPUID_LNX_4); + BUILD_BUG_ON(x86_leaf == CPUID_LNX_5); BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid)); BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0); }
Add CPUID_LNX_5 to track cpufeatures' word 21, and add the appropriate compile-time assert in KVM to prevent direct lookups on the features in CPUID_LNX_5. KVM uses X86_FEATURE_* flags to manage guest CPUID, and so must translate features that are scattered by Linux from the Linux-defined bit to the hardware-defined bit, i.e. should never try to directly access scattered features in guest CPUID. Opportunistically add NR_CPUID_WORDS to enum cpuid_leafs, along with a compile-time assert in KVM's CPUID infrastructure to ensure that future additions update cpuid_leafs along with NCAPINTS. No functional change intended. Fixes: 7f274e609f3d ("x86/cpufeatures: Add new word for scattered features") Cc: Sandipan Das <sandipan.das@amd.com> Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/include/asm/cpufeature.h | 2 ++ arch/x86/kvm/reverse_cpuid.h | 2 ++ 2 files changed, 4 insertions(+) base-commit: c85af715cac0a951eea97393378e84bb49384734