Re: [PATCH 01/22] x86/srso: Fix srso_show_state() side effect

[Nikolay Borisov]

On 21.08.23 г. 4:18 ч., Josh Poimboeuf wrote:
> Reading the 'spec_rstack_overflow' sysfs file can trigger an unnecessary
> MSR write, and possibly even a (handled) exception if the microcode
> hasn't been updated.
>
> Avoid all that by just checking X86_FEATURE_IBPB_BRTYPE instead, which
> gets set by srso_select_mitigation() if the updated microcode exists.
>
> Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
> Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> ---
>   arch/x86/kernel/cpu/bugs.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
> index f081d26616ac..bdd3e296f72b 100644
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -2717,7 +2717,7 @@ static ssize_t srso_show_state(char *buf)
>   
>   	return sysfs_emit(buf, "%s%s\n",
>   			  srso_strings[srso_mitigation],
> -			  (cpu_has_ibpb_brtype_microcode() ? "" : ", no microcode"));
> +			  boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) ? "" : ", no microcode");
>   }
>   
>   static ssize_t gds_show_state(char *buf)


Reviewed-by: Nikolay Borisov <nik.borisov@xxxxxxxx>