linux-kernel - Re: [PATCH v11 18/23] x86/resctrl: Report "Unassigned" for MBM events in mbm_cntr

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Message-ID: <00bf94f7-9992-4db1-a5c1-c2708defc806@amd.com>
Date: Mon, 10 Feb 2025 11:39:14 -0600
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, corbet@....net,
 tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, tony.luck@...el.com, peternewman@...gle.com
Cc: fenghua.yu@...el.com, x86@...nel.org, hpa@...or.com, paulmck@...nel.org,
 akpm@...ux-foundation.org, thuth@...hat.com, rostedt@...dmis.org,
 xiongwei.song@...driver.com, pawan.kumar.gupta@...ux.intel.com,
 daniel.sneddon@...ux.intel.com, jpoimboe@...nel.org, perry.yuan@....com,
 sandipan.das@....com, kai.huang@...el.com, xiaoyao.li@...el.com,
 seanjc@...gle.com, xin3.li@...el.com, andrew.cooper3@...rix.com,
 ebiggers@...gle.com, mario.limonciello@....com, james.morse@....com,
 tan.shaopeng@...itsu.com, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, maciej.wieczor-retman@...el.com,
 eranian@...gle.com
Subject: Re: [PATCH v11 18/23] x86/resctrl: Report "Unassigned" for MBM events
 in mbm_cntr_assign mode

Hi Reinette,

On 2/6/25 12:04, Reinette Chatre wrote:
> Hi Babu,
> 
> On 1/22/25 12:20 PM, Babu Moger wrote:
>> In mbm_cntr_assign mode, the hardware counter should be assigned to read
>> the MBM events.
>>
>> Report 'Unassigned' in case the user attempts to read the events without
>> assigning the counter.
>>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
> 
>> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
>> index 99cae75559b0..072b15550ff7 100644
>> --- a/Documentation/arch/x86/resctrl.rst
>> +++ b/Documentation/arch/x86/resctrl.rst
>> @@ -431,6 +431,16 @@ When monitoring is enabled all MON groups will also contain:
>>  	for the L3 cache they occupy). These are named "mon_sub_L3_YY"
>>  	where "YY" is the node number.
>>  
>> +	When supported the mbm_cntr_assign mode allows users to assign a
> 
> Same comment as previous version.

Sorry about that.

"mbm_cntr_assign mode allows users to assign a"


> 
>> +	counter to mon_hw_id, event pair enabling bandwidth monitoring for
>> +	as long as the counter remains assigned. The hardware will continue
>> +	tracking the assigned mon_hw_id until the user manually unassigns
>> +	it, ensuring that counters are not reset during this period. With
>> +	a limited number of counters, the system may run out of assignable
>> +	counters. In that case, MBM event counters will return 'Unassigned'
>> +	when the event is read. Users must manually assign a counter to read
>> +	the events.
>> +
>>  "mon_hw_id":
>>  	Available only with debug option. The identifier used by hardware
>>  	for the monitor group. On x86 this is the RMID.
> 
> Reinette
> 

-- 
Thanks
Babu Moger