linux-kernel - Re: [PATCH v14 19/32] fs/resctrl: Add the functionality to unassign MBM events

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Message-ID: <96297efd-0f65-4dde-9720-36dd9b689295@intel.com>
Date: Tue, 24 Jun 2025 20:38:35 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <tony.luck@...el.com>,
	<Dave.Martin@....com>, <james.morse@....com>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <akpm@...ux-foundation.org>,
	<rostedt@...dmis.org>, <paulmck@...nel.org>, <thuth@...hat.com>,
	<ardb@...nel.org>, <gregkh@...uxfoundation.org>, <seanjc@...gle.com>,
	<thomas.lendacky@....com>, <pawan.kumar.gupta@...ux.intel.com>,
	<manali.shukla@....com>, <perry.yuan@....com>, <kai.huang@...el.com>,
	<peterz@...radead.org>, <xiaoyao.li@...el.com>, <kan.liang@...ux.intel.com>,
	<mario.limonciello@....com>, <xin3.li@...el.com>, <gautham.shenoy@....com>,
	<xin@...or.com>, <chang.seok.bae@...el.com>, <fenghuay@...dia.com>,
	<peternewman@...gle.com>, <maciej.wieczor-retman@...el.com>,
	<eranian@...gle.com>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v14 19/32] fs/resctrl: Add the functionality to unassign
 MBM events

Hi Babu,

On 6/13/25 2:05 PM, Babu Moger wrote:
> The "mbm_event" mode offers "num_mbm_cntrs" number of counters that can be

"The "mbm_event" mode" -> "The "mbm_event" counter assignment mode"?

> 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>
> ---
...

> ---
>  fs/resctrl/internal.h |  2 ++
>  fs/resctrl/monitor.c  | 47 +++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 49 insertions(+)
> 
> diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
> index 0767a1c46f26..4496c359ac22 100644
> --- a/fs/resctrl/internal.h
> +++ b/fs/resctrl/internal.h
> @@ -388,6 +388,8 @@ int resctrl_find_cleanest_closid(void);
>  
>  int resctrl_assign_cntr_event(struct rdt_resource *r, struct rdt_mon_domain *d,
>  			      struct rdtgroup *rdtgrp, struct mon_evt *mevt);
> +void resctrl_unassign_cntr_event(struct rdt_resource *r, struct rdt_mon_domain *d,
> +				 struct rdtgroup *rdtgrp, struct mon_evt *mevt);
>  
>  #ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
>  int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp);
> diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
> index 38800fe45931..f2636aea6545 100644
> --- a/fs/resctrl/monitor.c
> +++ b/fs/resctrl/monitor.c
> @@ -1016,6 +1016,14 @@ 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(struct mbm_cntr_cfg));

sizeof(struct mbm_cntr_cfg) -> sizeof(*d->cntr_cfg[0])

> +}
> +
>  /**
>   * resctrl_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.
> @@ -1084,3 +1092,42 @@ int resctrl_assign_cntr_event(struct rdt_resource *r, struct rdt_mon_domain *d,
>  
>  	return ret;
>  }
> +
> +/**
> + * resctrl_free_config_cntr() - Unassign and reset the counter ID configuration
> + * for the event pointed to by @mevt within the domain @d and resctrl group @rdtgrp.
> + */
> +static void resctrl_free_config_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
> +				     struct rdtgroup *rdtgrp, struct mon_evt *mevt)
> +{
> +	int cntr_id;
> +
> +	cntr_id = mbm_cntr_get(r, d, rdtgrp, mevt->evtid);
> +
> +	/* If there is no cntr_id assigned, nothing to do */
> +	if (cntr_id < 0)
> +		return;
> +
> +	resctrl_config_cntr(r, d, mevt->evtid, rdtgrp->mon.rmid, rdtgrp->closid,
> +			    cntr_id, false);
> +
> +	mbm_cntr_free(d, cntr_id);
> +
> +	return;

No need for this return.

> +}
> +
> +/**
> + * resctrl_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 resctrl_unassign_cntr_event(struct rdt_resource *r, struct rdt_mon_domain *d,
> +				 struct rdtgroup *rdtgrp, struct mon_evt *mevt)
> +{
> +	if (!d) {
> +		list_for_each_entry(d, &r->mon_domains, hdr.list)
> +			resctrl_free_config_cntr(r, d, rdtgrp, mevt);
> +	} else {
> +		resctrl_free_config_cntr(r, d, rdtgrp, mevt);
> +	}
> +}

Reinette