linux-kernel - Re: [PATCH v15 08/34] x86,fs/resctrl: Detect Assignable Bandwidth Monitoring feature details

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Message-ID: <58532255-5e18-45fc-87de-fc8af9c12908@amd.com>
Date: Tue, 15 Jul 2025 11:53:29 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, corbet@....net,
 tony.luck@...el.com, james.morse@....com, tglx@...utronix.de,
 mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com
Cc: Dave.Martin@....com, x86@...nel.org, hpa@...or.com,
 akpm@...ux-foundation.org, paulmck@...nel.org, rostedt@...dmis.org,
 Neeraj.Upadhyay@....com, david@...hat.com, arnd@...db.de, fvdl@...gle.com,
 seanjc@...gle.com, jpoimboe@...nel.org, pawan.kumar.gupta@...ux.intel.com,
 xin@...or.com, manali.shukla@....com, tao1.su@...ux.intel.com,
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 peterz@...radead.org, xin3.li@...el.com, kan.liang@...ux.intel.com,
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Subject: Re: [PATCH v15 08/34] x86,fs/resctrl: Detect Assignable Bandwidth
 Monitoring feature details

Hi Reinette,

On 7/15/25 11:26, Reinette Chatre wrote:
> Hi Babu,
> 
> On 7/8/25 3:17 PM, Babu Moger wrote:
>> ABMC feature details are reported via CPUID Fn8000_0020_EBX_x5.
>> Bits Description
>> 15:0 MAX_ABMC Maximum Supported Assignable Bandwidth
>>      Monitoring Counter ID + 1
>>
>> The feature details are documented in APM listed below [1].
>> [1] AMD64 Architecture Programmer's Manual Volume 2: System Programming
>> Publication # 24593 Revision 3.41 section 19.3.3.3 Assignable Bandwidth
>> Monitoring (ABMC).
>>
>> Detect the feature and number of assignable counters supported. Also,
>> enable QOS_L3_MBM_TOTAL_EVENT_ID and QOS_L3_MBM_LOCAL_EVENT_ID upon
>> detecting the ABMC feature. The current expectation is to support
>> these two events by default when ABMC is enabled.
>>
> 
> Did the right patches make it out as part of this submission? The above
> changelog contains text that was removed per
> https://lore.kernel.org/lkml/aca368e0-0936-4852-9cf6-688931e0c65d@amd.com/

Yes. Code changes are taken care.

v15: Minor update to changelog.
     Added check in resctrl_cpu_detect().
     Moved the resctrl_enable_mon_event() to resctrl_mon_resource_init().


But missed the changelog. Sorry about that.


Here is the updated version.
--------------------------------

x86,fs/resctrl: Detect Assignable Bandwidth Monitoring feature details

ABMC feature details are reported via CPUID Fn8000_0020_EBX_x5.
Bits Description
15:0 MAX_ABMC Maximum Supported Assignable Bandwidth
     Monitoring Counter ID + 1

The feature details are documented in APM listed below [1].
[1] AMD64 Architecture Programmer's Manual Volume 2: System Programming
Publication # 24593 Revision 3.41 section 19.3.3.3 Assignable Bandwidth
Monitoring (ABMC).

Detect the feature and number of assignable counters supported. For
backward compatibility, upon detecting the assignable counter feature,
enable the mbm_total_bytes and mbm_local_bytes events that users are
familiar with as part of original L3 MBM support.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
Signed-off-by: Babu Moger <babu.moger@....com>

-- 
Thanks
Babu Moger