linux-kernel - Re: [PATCH V2 01/10] x86/CPU: Expose if cache is inclusive of lower level caches

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Date:   Tue, 6 Aug 2019 14:16:10 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     tglx@...utronix.de, fenghua.yu@...el.com, tony.luck@...el.com,
        kuo-lang.tseng@...el.com, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 01/10] x86/CPU: Expose if cache is inclusive of lower
 level caches

Hi Borislav,

On 8/6/2019 1:40 PM, Borislav Petkov wrote:
> On Tue, Aug 06, 2019 at 01:22:22PM -0700, Reinette Chatre wrote:
>> ... because some platforms differ in which SKUs support cache
>> pseudo-locking. On these platforms only the SKUs with inclusive cache
>> support cache pseudo-locking, thus the additional check.
> 
> Ok, so it sounds to me like that check in get_prefetch_disable_bits()
> should be extended (and maybe renamed) to check for cache inclusivity
> too, in order to know which platforms support cache pseudo-locking.

Indeed. As you pointed out this would be same system-wide and the check
thus need not be delayed until it is known which cache is being
pseudo-locked.

> I'd leave it to tglx to say how we should mirror cache inclusivity in
> cpuinfo_x86: whether a synthetic X86_FEATURE bit or cache the respective
> CPUID words which state whether L2/L3 is inclusive...

Thank you very much. I appreciate your guidance here.

Reinette