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

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Date: Thu, 14 Dec 2023 18:20:56 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: 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 v2 1/2] x86/resctrl: Remove hard-coded memory bandwidth
 limit

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>

Reinette