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Re: [PATCH v2 1/4] x86/microcode: Remove Intel's family check on early_microcode_init()


  • To: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Mon, 12 Jun 2023 17:16:44 +0200
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  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Mon, 12 Jun 2023 15:16:55 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 05.06.2023 19:08, Alejandro Vallejo wrote:

> --- a/xen/arch/x86/cpu/microcode/core.c
> +++ b/xen/arch/x86/cpu/microcode/core.c
> @@ -854,8 +854,14 @@ int __init early_microcode_init(unsigned long 
> *module_map,
>          break;
>  
>      case X86_VENDOR_INTEL:
> -        if ( c->x86 >= 6 )
> -            ucode_ops = intel_ucode_ops;
> +        /*
> +         * Intel introduced microcode loading with family 6. Because we
> +         * don't support compiling Xen for 32bit machines we're guaranteed
> +         * that at this point we're either in family 15 (Pentium 4) or 6
> +         * (everything since then), so microcode facilities are always
> +         * present.
> +         */
> +        ucode_ops = intel_ucode_ops;
>          break;
>      }

There are many places where we make such connections / assumptions without
long comments. I'd be okay with a brief one, but I'm not convinced we need
one at all.

Jan



 


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