linux-kernel - Re: [PATCH] x86/resctrl: fix min_cbm

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Date:   Mon, 16 May 2022 13:51:15 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Stephane Eranian <eranian@...gle.com>
CC:     <linux-kernel@...r.kernel.org>, <fenghua.yu@...el.com>,
        <babu.moger@....com>, "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH] x86/resctrl: fix min_cbm_bits for AMD

Hi Stephane,

On 5/16/2022 12:07 PM, Stephane Eranian wrote:
> On Mon, May 16, 2022 at 9:35 AM Reinette Chatre
> <reinette.chatre@...el.com> wrote:

...

>> Thank you very much for catching this. While the fix is onto something
>> I would prefer the fix to be obvious and not a side effect of bit
>> checking in an empty bitmap.
>>
> Are you asking for me to add a comment on the modified line or are you asking
> for a change in cbm_validate()? There, I could add an empty_bitmask check to
> that if.

Please check my original response for inline comments to your patch.

I am asking for a change in cbm_validate() and my response did include some
sample code copied below. 

>> Something like this before the bit parsing starts:
>>         if (r->cache.arch_has_empty_bitmaps && val == 0)
>>                 goto done;
>>
>>         /* Skip bit parsing */
>>
>> done:
>>         *data = val;
>>         return true;
>>

Reinette