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| author | Sean Christopherson <seanjc@google.com> | 2022-11-25 13:58:38 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-11-28 19:33:25 +0100 |
| commit | c4690d016182d271a862767145db8b2bc792f4a8 (patch) | |
| tree | fcd1642b971fb2eda321154a67ee7a81e6131138 /arch/x86/kvm/cpuid.c | |
| parent | MAINTAINERS: Add KVM x86/xen maintainer list (diff) | |
| download | linux-c4690d016182d271a862767145db8b2bc792f4a8.tar.xz linux-c4690d016182d271a862767145db8b2bc792f4a8.zip | |
KVM: x86: Add BUILD_BUG_ON() to detect bad usage of "scattered" flags
Add a compile-time assert in the SF() macro to detect improper usage,
i.e. to detect passing in an X86_FEATURE_* flag that isn't actually
scattered by the kernel. Upcoming feature flags will be 100% KVM-only
and will have X86_FEATURE_* macros that point at a kvm_only_cpuid_leafs
word, not a kernel-defined word. Using SF() and thus boot_cpu_has() for
such feature flags would access memory beyond x86_capability[NCAPINTS]
and at best incorrectly hide a feature, and at worst leak kernel state to
userspace.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20221125125845.1182922-2-jiaxi.chen@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/cpuid.c')
| -rw-r--r-- | arch/x86/kvm/cpuid.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 6b5912578edd..ff2e9734e5c1 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -65,7 +65,13 @@ u32 xstate_required_size(u64 xstate_bv, bool compacted) #define KVM_X86_FEATURE_AMD_PSFD (13*32+28) /* Predictive Store Forwarding Disable */ #define F feature_bit -#define SF(name) (boot_cpu_has(X86_FEATURE_##name) ? F(name) : 0) + +/* Scattered Flag - For features that are scattered by cpufeatures.h. */ +#define SF(name) \ +({ \ + BUILD_BUG_ON(X86_FEATURE_##name >= MAX_CPU_FEATURES); \ + (boot_cpu_has(X86_FEATURE_##name) ? F(name) : 0); \ +}) /* * Magic value used by KVM when querying userspace-provided CPUID entries and |