Re: [PATCH 1/5] x86: Remove x86 low level version check of microcode

[Jan Beulich <jbeulich@xxxxxxxx>]

On 05.04.2024 14:11, Fouad Hilly wrote:
> Remove microcode version check at Intel and AMD Level.
> Microcode version check will be at higher and common level.

"will be" reads as if you're removing logic here, to introduce some replacement
later. If so, that's going to be a transient regression, which needs avoiding.
Indeed ...

> --- a/xen/arch/x86/cpu/microcode/amd.c
> +++ b/xen/arch/x86/cpu/microcode/amd.c
> @@ -383,12 +383,8 @@ static struct microcode_patch *cf_check 
> cpu_request_microcode(
>                  goto skip;
>              }
>  
> -            /*
> -             * If the new ucode covers current CPU, compare ucodes and store 
> the
> -             * one with higher revision.
> -             */
> -            if ( (microcode_fits(mc->patch) != MIS_UCODE) &&
> -                 (!saved || (compare_header(mc->patch, saved) == NEW_UCODE)) 
> )
> +            /* If the provided ucode covers current CPU, then store its 
> revision. */
> +            if ( (microcode_fits(mc->patch) != MIS_UCODE) && !saved )
>              {
>                  saved = mc->patch;
>                  saved_size = mc->len;

... this looks like a logic change to me, with there not being anything
similar in common code afaics. Am I overlooking anything?

> --- a/xen/arch/x86/cpu/microcode/intel.c
> +++ b/xen/arch/x86/cpu/microcode/intel.c
> @@ -294,8 +294,7 @@ static int cf_check apply_microcode(const struct 
> microcode_patch *patch)
>  
>      result = microcode_update_match(patch);
>  
> -    if ( result != NEW_UCODE &&
> -         !(opt_ucode_allow_same && result == SAME_UCODE) )
> +    if ( result != NEW_UCODE && result != SAME_UCODE )
>          return -EINVAL;

I'm afraid I can't relate this adjustment with title and description of
the patch.

Jan