linux-kernel - Re: [PATCH 2/2] amd: uncore: Get correct number of cores sharing last level cache

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Date:   Tue, 6 Jun 2017 18:01:33 -0500
From:   Janakarajan Natarajan <jnataraj@....com>
To:     Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Janakarajan Natarajan <Janakarajan.Natarajan@....com>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: Re: [PATCH 2/2] amd: uncore: Get correct number of cores sharing last
 level cache


On 06/06/2017 12:45 PM, Borislav Petkov wrote:
> On Tue, Jun 06, 2017 at 12:15:30PM +0200, Peter Zijlstra wrote:
>> Maybe something like:
>>
>> 	for (cache_level = 0; cache_level < 3; cache_level++) {
>> 		cpuid_count(0x8000001d, cache_level, &eax, &ebx, &ecx, &edx);
>>
>> 		if ((eax & 0x1f) == 0) /* EAX[0:4] gives cache type */
> 		if (!(eax & 0x1f))
>
>> 			break;
>>
>> 		prev_eax = eax;
>> 	}
>>
>> That way we'll not run off into the woods if CPUID goes funny (never
>> trust a BIOS/virt monkey).
> Yap, especially if there are CPUID functions with subleafs with holes in
> them.
Okay. I can send a v2 with the changes.
>