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Re: [PATCH v2 1/4] x86/microcode: Remove Intel's family check on early_microcode_init()
- To: Jan Beulich <jbeulich@xxxxxxxx>, Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Mon, 12 Jun 2023 18:31:13 +0100
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 12 Jun 2023 17:31:50 +0000
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On 12/06/2023 4:16 pm, Jan Beulich wrote:
> 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.
I agree. I don't think we need a comment here.
I'd also tweak the commit message to say "All 64bit-capable Intel CPUs
are supported as far as microcode loading goes" or similar. It's subtly
different IMO.
The Intel microcode driver already relies on 64bit-ness to exclude and
early case (on 32bit CPUs only) which lack Platform Flags.
I'm happy to fix both of these up on commit.
~Andrew
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