linux-kernel - Re: [PATCH v15 21/34] x86/resctrl: Refactor resctrl_arch_rmid

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Message-ID: <afb94c18-9de5-4d33-b99e-53dcdebeae95@amd.com>
Date: Tue, 22 Jul 2025 10:25:57 -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,
 sohil.mehta@...el.com, kai.huang@...el.com, xiaoyao.li@...el.com,
 peterz@...radead.org, xin3.li@...el.com, kan.liang@...ux.intel.com,
 mario.limonciello@....com, thomas.lendacky@....com, perry.yuan@....com,
 gautham.shenoy@....com, chang.seok.bae@...el.com, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, peternewman@...gle.com, eranian@...gle.com
Subject: Re: [PATCH v15 21/34] x86/resctrl: Refactor resctrl_arch_rmid_read()

Hi Reinette,

On 7/22/25 09:56, Reinette Chatre wrote:
> Hi Babu,
> 
> On 7/22/25 7:23 AM, Moger, Babu wrote:
>> Hi Reinette,
>>
>>
>> On 7/17/25 22:51, Reinette Chatre wrote:
>>> Hi Babu,
>>>
>>> On 7/8/25 3:17 PM, Babu Moger wrote:
>>>> resctrl_arch_rmid_read() modifies the value obtained from MSR_IA32_QM_CTR
>>>> to account for overflow. This adjustment is common to both
>>>
>>> The portion factored out does not just handle MBM overflow counts but also
>>> handles counter scaling for *all* events, including cache occupancy.
>>
>> Yes. Got it. thanks
>>
>>>
>>>> resctrl_arch_rmid_read() and resctrl_arch_cntr_read().
>>>>
>>>> To prepare for the implementation of resctrl_arch_cntr_read(), refactor
>>>> this logic into a new function called mbm_corrected_val().
>>>
>>> This thus cannot be made specific to MBM. More accurate may be
>>> get_corrected_val().
>>
>> Sure.
>>
>> Rephrased the changelog.
>>
>> x86/resctrl: Refactor resctrl_arch_rmid_read()
>>
>> resctrl_arch_rmid_read() modifies the value obtained from MSR_IA32_QM_CTR
> 
> "modifies" -> "adjusts"?

Sure.

> 
>> to account for the overflow for MBM events and apply counter scaling for
>> all the events. This logic is common to both resctrl_arch_rmid_read() and
>> resctrl_arch_cntr_read().
> 
> This may not be obvious since resctrl_arch_cntr_read() does not exist at this
> point in the series. Perhaps just make it a bit higher level, for example:
> "This logic is common to both reading an RMID and reading a hardware counter
> directly."
> 
Sure.

>>
>> To prepare for the implementation of resctrl_arch_cntr_read(), refactor
>> this logic into a new function called get_corrected_val().
> 
> No need for "function" when using (). Could be :
> "Refactor the hardware value adjustment logic into get_corrected_val() to
> prepare for support of reading a hardware counter."?
> 

Sure

-- 
Thanks
Babu Moger