linux-kernel - Re: [PATCH v7 06/24] x86/resctrl: Add support to enable/disable AMD ABMC feature

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Message-ID: <56f1396e-8a51-43d3-9dd0-dc55a1623b12@intel.com>
Date: Thu, 19 Sep 2024 09:22:06 -0700
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>,
	<yanjiewtw@...il.com>, <kim.phillips@....com>, <lukas.bulwahn@...il.com>,
	<seanjc@...gle.com>, <jmattson@...gle.com>, <leitao@...ian.org>,
	<jpoimboe@...nel.org>, <rick.p.edgecombe@...el.com>,
	<kirill.shutemov@...ux.intel.com>, <jithu.joseph@...el.com>,
	<kai.huang@...el.com>, <kan.liang@...ux.intel.com>,
	<daniel.sneddon@...ux.intel.com>, <pbonzini@...hat.com>,
	<sandipan.das@....com>, <ilpo.jarvinen@...ux.intel.com>,
	<peternewman@...gle.com>, <maciej.wieczor-retman@...el.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<eranian@...gle.com>, <james.morse@....com>
Subject: Re: [PATCH v7 06/24] x86/resctrl: Add support to enable/disable AMD
 ABMC feature

Hi Babu,

On 9/4/24 3:21 PM, Babu Moger wrote:
> Add the functionality to enable/disable AMD ABMC feature.
> 
> AMD ABMC feature is enabled by setting enabled bit(0) in MSR
> L3_QOS_EXT_CFG.  When the state of ABMC is changed, the MSR needs
> to be updated on all the logical processors in the QOS Domain.
> 
> Hardware counters will reset when ABMC state is changed. Reset the
> architectural state maintained by resctrl so that reading of a hardware
> counter is not considered as an overflow in next update.

Above mentions that architectural state is also reset, but that does
not seem to form part of this patch? 

> 
> The ABMC feature details are documented in APM listed below [1].
> [1] AMD64 Architecture Programmer's Manual Volume 2: System Programming
> Publication # 24593 Revision 3.41 section 19.3.3.3 Assignable Bandwidth
> Monitoring (ABMC).
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---

...

>  static inline struct rdt_hw_resource *resctrl_to_arch_res(struct rdt_resource *r)
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 7e76f8d839fc..0178555bf3f6 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -2402,6 +2402,41 @@ int resctrl_arch_set_cdp_enabled(enum resctrl_res_level l, bool enable)
>  	return 0;
>  }
>  
> +/*
> + * Update L3_QOS_EXT_CFG MSR on all the CPUs associated with the resource.

This comment is not accurate since the function below only sets MSR on current CPU.

> + */
> +static void resctrl_abmc_set_one_amd(void *arg)

Reinette