Re: [PATCH v1 2/3] x86/cpu: Set low performance CRC32C flag on some Zhaoxin CPUs

Tony W Wang-oc
2021-01-11T10:55:01Z

On 07/01/2021 23:52, Dave Hansen wrote:
> On 1/6/21 10:19 PM, Tony W Wang-oc wrote:
>> + /*
>> + * These CPUs declare support SSE4.2 instruction sets but
>> + * having low performance CRC32C instruction implementation.
>> + */
>> + if (c->x86 == 0x6 || (c->x86 == 0x7 && c->x86_model <= 0x3b))
>> + set_cpu_cap(c, X86_FEATURE_CRC32C);
>> }
>
> On the Intel side, we've tried to move away from open-coded model
> numbers. Say another CPU is released that has a microarchitecture close
> to 0x3b, but has a model of 0x3c. It's a *LOT* easier to grep for
> INTEL_FAM6_NEHALEM (or whatever) than 0x3c. See:
>
> arch/x86/include/asm/intel-family.h
>
> for examples.
> .
>

Got it, thanks for your suggestion.

Sincerely
Tonyw