linux-kernel - Re: [PATCH v5 2/2] x86/resctrl: Read supported bandwidth sources using CPUID command

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Date: Tue, 16 Jan 2024 15:39:25 -0600
From: "Moger, Babu" <bmoger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>,
 Babu Moger <babu.moger@....com>, corbet@....net, fenghua.yu@...el.com,
 tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com
Cc: x86@...nel.org, hpa@...or.com, paulmck@...nel.org, rdunlap@...radead.org,
 tj@...nel.org, peterz@...radead.org, seanjc@...gle.com,
 kim.phillips@....com, jmattson@...gle.com, ilpo.jarvinen@...ux.intel.com,
 jithu.joseph@...el.com, kan.liang@...ux.intel.com, nikunj@....com,
 daniel.sneddon@...ux.intel.com, pbonzini@...hat.com,
 rick.p.edgecombe@...el.com, rppt@...nel.org,
 maciej.wieczor-retman@...el.com, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, eranian@...gle.com, peternewman@...gle.com,
 dhagiani@....com
Subject: Re: [PATCH v5 2/2] x86/resctrl: Read supported bandwidth sources
 using CPUID command

Hi Reinette,

On 1/16/2024 1:44 PM, Reinette Chatre wrote:
> Hi Babu,
>
> On 1/15/2024 2:52 PM, Babu Moger wrote:
>> If the BMEC (Bandwidth Monitoring Event Configuration) feature is
>> supported, the bandwidth events can be configured. The maximum supported
>> bandwidth bitmask can be determined by following CPUID command.
>>
>> CPUID_Fn80000020_ECX_x03 [Platform QoS Monitoring Bandwidth Event
>> Configuration] Read-only. Reset: 0000_007Fh.
>> Bits    Description
>> 31:7    Reserved
>>   6:0    Identifies the bandwidth sources that can be tracked.
>>
>> The bandwidth sources can change with the processor generations.
>> Read the supported bandwidth sources using the CPUID command.
>>
>> While at it, move the mask checking to mon_config_write() before
>> iterating over all the domains. Also, print the valid bitmask when
>> the user tries to configure invalid event configuration value.
>>
>> The CPUID details are documented in the PPR listed below [1].
>> [1] Processor Programming Reference (PPR) Vol 1.1 for AMD Family 19h Model
>> 11h B1 - 55901 Rev 0.25.
>>
>> Fixes: dc2a3e857981 ("x86/resctrl: Add interface to read mbm_total_bytes_config")
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
>> ---
> Thank you.
>
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>


Thank you

Babu Moger