Re: [PATCH v3 4/4] x86/cpu/topology: Check for X86_FEATURE_XTOPOLOGY instead of passing has_topoext

[K Prateek Nayak <kprateek.nayak@amd.com>]

Hello Thomas,

On 8/24/2025 8:25 PM, Thomas Gleixner wrote:
> On Sun, Aug 24 2025 at 15:38, Thomas Gleixner wrote:
>>> -	if (!has_topoext) {
>>> +	if (!cpu_feature_enabled(X86_FEATURE_XTOPOLOGY)) {
>>>  		/*
>>>  		 * Prefer initial_apicid parsed from XTOPOLOGY leaf
>>>  		 * 0x8000026 or 0xb if available. Otherwise prefer the
>>
>> That's patently wrong.
>>
>> The leaves might be "available", but are not guaranteed to be valid. So
>> FEATURE_XTOPOLOGY gives you the wrong answer.
>>
>> The has_topoext logic is there for a reason.
> 
> Hrm. I have to correct myself. It's set by the 0xb... parsing when that
> finds a valid leaf. My memory tricked me on that.
> 
> So yes, it can be used for that, but that's a cleanup. The simple fix
> should be applied first as that's trivial to backport.

Thank you for taking a look at the series. I'll move the fixes ahead and
refresh the current Patch 2 with your suggested diff in the next
version.

-- 
Thanks and Regards,
Prateek