linux-kernel - Re: [PATCH v2 1/2] x86/resctrl: Remove hard-coded memory bandwidth limit

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Message-ID: <78494d57-40cf-4604-b1b6-8d94ca1c9973@amd.com>
Date: Tue, 2 Jan 2024 13:52:27 -0600
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.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 v2 1/2] x86/resctrl: Remove hard-coded memory bandwidth
 limit

Hi Reinette,

On 12/14/23 20:20, Reinette Chatre wrote:
> Hi Babu,
> 
> On 12/12/2023 10:02 AM, Babu Moger wrote:
>> The QOS Memory Bandwidth Enforcement Limit is reported by
>> CPUID_Fn80000020_EAX_x01 and CPUID_Fn80000020_EAX_x02.
>> Bits Description
>> 31:0 BW_LEN: Size of the QOS Memory Bandwidth Enforcement Limit.
>>
>> Newer processors can support higher bandwidth limit than the current
>> hard-coded value. Remove the hard-coded value and detect using CPUID
>> command. Also update the register variables eax and edx to match the
>> AMD CPUID definition.
>>
>> The CPUID details are documentation 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: 4d05bf71f157 ("x86/resctrl: Introduce AMD QOS feature")
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
>> Signed-off-by: Babu Moger <babu.moger@....com>
>>
>> ---
> 
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>

Thank You
Babu Moger