Re: [PATCH v4 04/17] x86/split_lock: Align x86_capability to unsigned long to avoid split locked access

Dave Hansen
2019-03-04T18:52:19Z

On 3/1/19 6:44 PM, Fenghua Yu wrote:
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 33051436c864..eb8ae701ef65 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -93,7 +93,9 @@ struct cpuinfo_x86 {
> __u32 extended_cpuid_level;
> /* Maximum supported CPUID level, -1=no CPUID: */
> int cpuid_level;
> - __u32 x86_capability[NCAPINTS + NBUGINTS];
> + /* Unsigned long alignment to avoid split lock in atomic bitmap ops */
> + __u32 x86_capability[NCAPINTS + NBUGINTS]
> + __aligned(sizeof(unsigned long));

I think this also warrants a comment in the changelog about the
alignment of 'struct cpuinfo_x86'.