Re: [PATCH v2 05/17] x86/cpu/intel: Fix page copy performance for extended Families

[Sohil Mehta]

On 2/13/2025 3:02 PM, Andrew Cooper wrote:
> On 12/02/2025 9:19 pm, Sohil Mehta wrote:
>> Check 1 (Based on Family Model numbers):
>>> /*
>>>  * Unconditionally set REP_GOOD on early Family 6 processors
>>>  */
>>> if (IS_ENABLED(CONFIG_X86_64) &&
>>>     (c->x86_vfm >= INTEL_PENTIUM_PRO && c->x86_vfm < INTEL_PENTIUM_M_DOTHAN))
>>> 	set_cpu_cap(c, X86_FEATURE_REP_GOOD);
>> This check is mostly redundant since it is targeted for 64 bit and very
>> few if any of those CPUs support 64 bit processing. I suggest that we
>> get rid of this check completely. The risk here is fairly limited as well.
> 
> PENTIUM_PRO is model 0x1.  M_DOTHAN isn't introduced until patch 10, but
> is model 0xd.
> 
> And model 0xf (Memron) is the first 64bit capable fam6 CPU, so this is
> dead code given the CONFIG_X86_64 which the compiler can't actually
> optimise out.
> 

Thanks for confirming. I figured this is likely dead code but wasn't
completely sure.