linux-kernel - Re: [PATCH v17 30/33] fs/resctrl: Disable BMEC event configuration when mbm

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Message-ID: <78e5640d-b290-4a9b-a410-c44290f14e0b@intel.com>
Date: Tue, 2 Sep 2025 20:01:38 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <tony.luck@...el.com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>
CC: <Dave.Martin@....com>, <james.morse@....com>, <x86@...nel.org>,
	<hpa@...or.com>, <akpm@...ux-foundation.org>, <rostedt@...dmis.org>,
	<paulmck@...nel.org>, <pawan.kumar.gupta@...ux.intel.com>, <kees@...nel.org>,
	<arnd@...db.de>, <fvdl@...gle.com>, <seanjc@...gle.com>,
	<thomas.lendacky@....com>, <yosry.ahmed@...ux.dev>, <xin@...or.com>,
	<sohil.mehta@...el.com>, <kai.huang@...el.com>, <xiaoyao.li@...el.com>,
	<peterz@...radead.org>, <mario.limonciello@....com>, <xin3.li@...el.com>,
	<perry.yuan@....com>, <chang.seok.bae@...el.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<peternewman@...gle.com>, <eranian@...gle.com>, <gautham.shenoy@....com>
Subject: Re: [PATCH v17 30/33] fs/resctrl: Disable BMEC event configuration
 when mbm_event mode is enabled

Hi Babu,

On 8/14/25 7:25 PM, Babu Moger wrote:
> The BMEC (Bandwidth Monitoring Event Configuration) feature enables
> per-domain event configuration. With BMEC the MBM events are configured
> using the mbm_total_bytes_config or mbm_local_bytes_config files in
> /sys/fs/resctrl/info/L3_MON/ and the per-domain event configuration affects
> all monitor resource groups.
> 
> The mbm_event counter assignment mode enables counters to be assigned to
> RMID (i.e a monitor resource group), event pairs, with potentially unique
> event configurations associated with every counter.
> 
> There may be systems that support both BMEC and mbm_event counter
> assignment mode, but resctrl supporting both concurrently will present a
> conflicting interface to the user with both per-domain and per RMID, event
> configurations active at the same time.
> 
> The mbm_event counter assignment provides most flexibility to user space
> and aligns with Arm's counter support. On systems that support both,
> disable BMEC event configuration when mbm_event mode is enabled by hiding
> the mbm_total_bytes_config or mbm_local_bytes_config files when mbm_event
> mode is enabled. Ensure mon_features always displays accurate information
> about monitor features.
> 
> Suggested-by: Reinette Chatre <reinette.chatre@...el.com>
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---

Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>

Reinette