linux-kernel - Re: [PATCH v11 04/13] x86/cpufeatures: Add Bandwidth Monitoring Event Configuration feature flag

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Message-ID: <2cf1380e-ed98-d943-e492-ebbe9238b51c@amd.com>
Date:   Tue, 24 Jan 2023 13:03:32 -0600
From:   "Moger, Babu" <babu.moger@....com>
To:     Reinette Chatre <reinette.chatre@...el.com>,
        Borislav Petkov <bp@...en8.de>
Cc:     "Luck, Tony" <tony.luck@...el.com>,
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Subject: Re: [PATCH v11 04/13] x86/cpufeatures: Add Bandwidth Monitoring Event
 Configuration feature flag


On 1/24/23 11:47, Reinette Chatre wrote:
> Hi Babu,
>
> On 1/24/2023 9:30 AM, Moger, Babu wrote:
>> On 1/24/23 10:59, Reinette Chatre wrote:
>>> On 1/24/2023 8:06 AM, Moger, Babu wrote:
>>>> On 1/24/23 09:10, Borislav Petkov wrote:
>>>>> On Tue, Jan 24, 2023 at 08:11:21AM -0600, Moger, Babu wrote:
>>>>>> Understood. I am planning to add resctrl feature list inside
>>>>>> /sys/fs/resctrl/info/ in my next series.
>>>>> Maybe I wasn't as clear as I hoped for:
>>>>>
>>>>> so you have a couple of flags in /proc/cpuinfo which are actively being used by
>>>>> tools.
>>>> Those flags will be there. Not planning to remove them.
>>>>> Why would you want to move the flags somewhere else and do the extra work for no
>>>>> apparent reason?
>>>> With this series(v12) we have added two new cpuid features(SMBA and BMEC).
>>>>
>>>> But these features are not visible in /proc/cpuinfo. Planning to add them
>>>> in /sys/fs/resctrl/info.
>>>>
>>>> So, users can see them here. 
>>> Could you please elaborate what you are planning to do? 
>> Yes. It is sort of available. But, I wanted to add them explicit using the
>> already available function rdt_cpu_has().
>>
>> Something like.
>>
>> #cat /sys/fs/resctrl/info/features
>>
>>  cmt, mbmtotal, mbmlocal, l3cat, mba, smba, bmec
>>
>>
>> Some of these features can be disabled using boot parameter options. So,
>> this will show only the features which enabled. 
>>
> From what I understand the only feature that needs additional help is CDP
> and it appears in /proc/cpuinfo. For all other features
> /sys/fs/resctrl/info already provides information when they are enabled, no?

Yes. It is available.  But, the feature BMEC is not explicitly available.
I was thinking making all of them explicit. But we can live with that for
now. We can think about this in the future. Thanks for the comments.

Thanks

Babu

> Reinette
>
-- 
Thanks
Babu Moger