linux-kernel - Re: [PATCH v15 18/34] fs/resctrl: Add the functionality to unassign MBM events

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Message-ID: <0689794b-994e-4644-a47f-595a3297a057@intel.com>
Date: Thu, 17 Jul 2025 20:48:32 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <tony.luck@...el.com>,
	<james.morse@....com>, <tglx@...utronix.de>, <mingo@...hat.com>,
	<bp@...en8.de>, <dave.hansen@...ux.intel.com>
CC: <Dave.Martin@....com>, <x86@...nel.org>, <hpa@...or.com>,
	<akpm@...ux-foundation.org>, <paulmck@...nel.org>, <rostedt@...dmis.org>,
	<Neeraj.Upadhyay@....com>, <david@...hat.com>, <arnd@...db.de>,
	<fvdl@...gle.com>, <seanjc@...gle.com>, <jpoimboe@...nel.org>,
	<pawan.kumar.gupta@...ux.intel.com>, <xin@...or.com>,
	<manali.shukla@....com>, <tao1.su@...ux.intel.com>, <sohil.mehta@...el.com>,
	<kai.huang@...el.com>, <xiaoyao.li@...el.com>, <peterz@...radead.org>,
	<xin3.li@...el.com>, <kan.liang@...ux.intel.com>,
	<mario.limonciello@....com>, <thomas.lendacky@....com>, <perry.yuan@....com>,
	<gautham.shenoy@....com>, <chang.seok.bae@...el.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<peternewman@...gle.com>, <eranian@...gle.com>
Subject: Re: [PATCH v15 18/34] fs/resctrl: Add the functionality to unassign
 MBM events

Hi Babu,

On 7/8/25 3:17 PM, Babu Moger wrote:
> The "mbm_event" counter assignment mode offers "num_mbm_cntrs" number of
> counters that can be assigned to RMID, event pairs and monitor bandwidth
> usage as long as it is assigned. If all the counters are in use, the
> kernel logs the error message "Unable to allocate counter in domain" in
> /sys/fs/resctrl/info/last_cmd_status when a new assignment is requested.
> 
> To make space for a new assignment, users must unassign an already
> assigned counter and retry the assignment again.
> 
> Add the functionality to unassign and free the counters in the domain.
> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---

...

> diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
> index bb074773420d..6c0410cf0195 100644
> --- a/fs/resctrl/monitor.c
> +++ b/fs/resctrl/monitor.c
> @@ -1022,6 +1022,14 @@ static int mbm_cntr_alloc(struct rdt_resource *r, struct rdt_mon_domain *d,
>  	return -ENOSPC;
>  }
>  
> +/*
> + * mbm_cntr_free() - Clear the counter ID configuration details in the domain @d.
> + */
> +static void mbm_cntr_free(struct rdt_mon_domain *d, int cntr_id)
> +{
> +	memset(&d->cntr_cfg[cntr_id], 0, sizeof(*d->cntr_cfg));
> +}
> +
>  /*
>   * rdtgroup_alloc_config_cntr() - Allocate a counter ID and configure it for the
>   * event pointed to by @mevt and the resctrl group @rdtgrp within the domain @d.
> @@ -1083,3 +1091,42 @@ int rdtgroup_assign_cntr_event(struct rdt_mon_domain *d, struct rdtgroup *rdtgrp
>  
>  	return ret;
>  }
> +
> +/*
> + * rdtgroup_free_config_cntr() - Unassign and reset the counter ID configuration

rdtgroup_free_config_cntr() -> rdtgroup_free_unassign_cntr() ?

> + * for the event pointed to by @mevt within the domain @d and resctrl group @rdtgrp.

@mevt -> @evtid

> + */
> +static void rdtgroup_free_config_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
> +				      struct rdtgroup *rdtgrp, enum resctrl_event_id evtid)
> +{
> +	int cntr_id;
> +
> +	cntr_id = mbm_cntr_get(r, d, rdtgrp, evtid);
> +
> +	/* If there is no cntr_id assigned, nothing to do */
> +	if (cntr_id < 0)
> +		return;
> +
> +	resctrl_config_cntr(r, d, evtid, rdtgrp->mon.rmid, rdtgrp->closid,
> +			    cntr_id, false);
> +
> +	mbm_cntr_free(d, cntr_id);
> +}
> +
> +/*
> + * rdtgroup_unassign_cntr_event() - Unassign a hardware counter associated with
> + * the event structure @mevt from the domain @d and the group @rdtgrp. Unassign
> + * the counters from all the domains if @d is NULL else unassign from @d.
> + */
> +void rdtgroup_unassign_cntr_event(struct rdt_mon_domain *d, struct rdtgroup *rdtgrp,
> +				  struct mon_evt *mevt)
> +{
> +	struct rdt_resource *r = resctrl_arch_get_resource(mevt->rid);
> +
> +	if (!d) {
> +		list_for_each_entry(d, &r->mon_domains, hdr.list)
> +			rdtgroup_free_config_cntr(r, d, rdtgrp, mevt->evtid);
> +	} else {
> +		rdtgroup_free_config_cntr(r, d, rdtgrp, mevt->evtid);
> +	}
> +}

Reinette