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>
#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