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 11:30:31 -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>,
        "corbet@....net" <corbet@....net>,
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        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
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Subject: Re: [PATCH v11 04/13] x86/cpufeatures: Add Bandwidth Monitoring Event
 Configuration feature flag


On 1/24/23 10:59, Reinette Chatre wrote:
> Hi Babu,
>
> 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. 

Thanks

Babu

>
> Existence and support for SMBA and BMEC is already visible to user space
> in your current series:
> * On a system that supports SMBA with the needed kernel support users will
>   find the /sys/fs/resctrl/info/SMBA directory with enumerated properties
>   as well as SMBA within the schemata file.
> * On a system that supports BMEC with the needed kernel support users will
>   find the relevant files listed within /sys/fs/resctrl/info/L3_MON/mon_features.
>
> Reinette

-- 
Thanks
Babu Moger