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

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Message-ID: <81fcb5c2-34cd-424d-8daa-582196726e30@amd.com>
Date: Thu, 26 Jun 2025 16:12:34 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.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 Reinette,

On 6/24/25 22:38, Reinette Chatre wrote:
> 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"?

Sure.

> 
>> 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])

Sure. Changed it to.

memset(&d->cntr_cfg[cntr_id], 0, sizeof(*d->cntr_cfg));


> 
>> +}
>> +
>>  /**
>>   * 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.

Sure.

> 
>> +}
>> +
>> +/**
>> + * 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
> 

-- 
Thanks
Babu Moger