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 11:44:12 -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 v5 2/2] x86/resctrl: Read supported bandwidth sources
 using CPUID command

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>

Reinette