On 12/09/16 07:32, Kirill A. Shutemov wrote: > > Something like this? > > diff --git a/arch/x86/boot/cpuflags.c b/arch/x86/boot/cpuflags.c > index 6687ab953257..366aad972025 100644 > --- a/arch/x86/boot/cpuflags.c > +++ b/arch/x86/boot/cpuflags.c > @@ -70,16 +70,22 @@ int has_eflag(unsigned long mask) > # define EBX_REG "=b" > #endif > > -static inline void cpuid(u32 id, u32 *a, u32 *b, u32 *c, u32 *d) > +static inline void cpuid_count(u32 id, u32 count, > + u32 *a, u32 *b, u32 *c, u32 *d) > { > + *a = id; > + *c = count; These two lines are wrong, remove them. > asm volatile(".ifnc %%ebx,%3 ; movl %%ebx,%3 ; .endif \n\t" > "cpuid \n\t" > ".ifnc %%ebx,%3 ; xchgl %%ebx,%3 ; .endif \n\t" > : "=a" (*a), "=c" (*c), "=d" (*d), EBX_REG (*b) > - : "a" (id) > + : "a" (id), "c" (count) > ); > } > > +#define cpuid(id, a, b, c, d) cpuid_count(id, 0, a, b, c, d) > + Other than that, it's correct. That being said, the claim that ECX ought to be zeroed on a non-subleaf-equipped CPUID leaf is spurious, in my opinion. That being said, it also doesn't do any harm and might avoid problems in the opposite direction, e.g. someone thinking that leaf 7 doesn't have subleaves. It might also be better to have something like: #define SAVE_EBX(x) ".ifnc %%ebx," x "; movl %%ebx," x "; .endif" #define SWAP_EBX(x) ".ifnc %%ebx," x "; xchgl %%ebx," x "; .endif" ... but if it is only used once it might just be more confusion. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html