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

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Date:   Tue, 24 Jan 2023 09:47:57 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     <babu.moger@....com>, Borislav Petkov <bp@...en8.de>
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Subject: Re: [PATCH v11 04/13] x86/cpufeatures: Add Bandwidth Monitoring Event
 Configuration feature flag

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?

Reinette