Message-ID: <74e08aa1-cb04-4002-9f98-a1eadbfe6869@amd.com>
Date: Mon, 21 Jul 2025 14:54:13 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.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 17/34] fs/resctrl: Add the functionality to assign MBM
 events

Hi Reinette,

On 7/17/25 22:47, Reinette Chatre wrote:
> Hi Babu,
> 
> On 7/8/25 3:17 PM, Babu Moger wrote:
>> When supported, "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.
>>
>> Add the functionality to allocate and assign a counter to an RMID, event
>> pair in the domain.
>>
>> If all the counters are in use, kernel will log the error message "Unable
>> to allocate counter in domain" in /sys/fs/resctrl/info/last_cmd_status
>> when a new assignment is requested. Exit on the first failure when
>> assigning counters across all the domains.
>>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
> 
> ...
> 
>> ---
>>  fs/resctrl/internal.h |   3 +
>>  fs/resctrl/monitor.c  | 131 ++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 134 insertions(+)
>>
>> diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
>> index ea5c9fa932aa..8879e127a8b8 100644
>> --- a/fs/resctrl/internal.h
>> +++ b/fs/resctrl/internal.h
>> @@ -387,6 +387,9 @@ bool closid_allocated(unsigned int closid);
>>  
>>  int resctrl_find_cleanest_closid(void);
>>  
>> +int rdtgroup_assign_cntr_event(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 11327bd8cf72..bb074773420d 100644
>> --- a/fs/resctrl/monitor.c
>> +++ b/fs/resctrl/monitor.c
>> @@ -952,3 +952,134 @@ void resctrl_mon_resource_exit(void)
>>  
>>  	dom_data_exit(r);
>>  }
>> +
>> +/*
>> + * resctrl_config_cntr() - Configure the counter ID for the event, RMID pair in
>> + * the domain.
>> + *
>> + * Assign the counter if @assign is true else unassign the counter. Reset the
>> + * associated non-architectural state.
> 
> Is this API only for assignment? It seems so. Looks like resctrl_config_cntr() is used
> for assign/unassign while rdtgroup_update_cntr_event()/resctrl_update_cntr_allrdtgrp() is
> for re-configure.
> 
> I think this will be easier to understand if the function names and comments match this
> usage. To help make clear when a counter is assigned/unassigned or when an assigned
> counter is re-configured.
> 
> resctrl_config_cntr() can be renamed to rdtgroup_assign_cntr() with its description
> matching what it does: (a) it does not reconfigure a counter but assign/unassign it,
> and (b) it operates on the rdtgroup.

Sure. Renamed it to rdtgroup_assign_cntr()

> It is only the underlying arch API that uses "configure" for assign, unassign, as
> well as configure.
> 
> 
>> + */
>> +static void resctrl_config_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
>> +				enum resctrl_event_id evtid, u32 rmid, u32 closid,
>> +				u32 cntr_id, bool assign)
>> +{
>> +	struct mbm_state *m;
>> +
>> +	resctrl_arch_config_cntr(r, d, evtid, rmid, closid, cntr_id, assign);
>> +
>> +	m = get_mbm_state(d, closid, rmid, evtid);
>> +	if (m)
>> +		memset(m, 0, sizeof(*m));
>> +}
>> +
>> +/*
>> + * mbm_cntr_get() - Return the counter ID for the matching @evtid and @rdtgrp.
>> + *
>> + * Return:
>> + * Valid counter ID on success, or -ENOENT on failure.
>> + */
>> +static int mbm_cntr_get(struct rdt_resource *r, struct rdt_mon_domain *d,
>> +			struct rdtgroup *rdtgrp, enum resctrl_event_id evtid)
>> +{
>> +	int cntr_id;
>> +
>> +	if (!r->mon.mbm_cntr_assignable)
>> +		return -ENOENT;
>> +
>> +	if (!resctrl_is_mbm_event(evtid))
>> +		return -ENOENT;
>> +
>> +	for (cntr_id = 0; cntr_id < r->mon.num_mbm_cntrs; cntr_id++) {
>> +		if (d->cntr_cfg[cntr_id].rdtgrp == rdtgrp &&
>> +		    d->cntr_cfg[cntr_id].evtid == evtid)
>> +			return cntr_id;
>> +	}
>> +
>> +	return -ENOENT;
>> +}
>> +
>> +/*
>> + * mbm_cntr_alloc() - Initialize and return a new counter ID in the domain @d.
>> + * Caller must ensure that the specified event is not assigned already.
>> + *
>> + * Return:
>> + * Valid counter ID on success, or -ENOSPC on failure.
>> + */
>> +static int mbm_cntr_alloc(struct rdt_resource *r, struct rdt_mon_domain *d,
>> +			  struct rdtgroup *rdtgrp, enum resctrl_event_id evtid)
>> +{
>> +	int cntr_id;
>> +
>> +	for (cntr_id = 0; cntr_id < r->mon.num_mbm_cntrs; cntr_id++) {
>> +		if (!d->cntr_cfg[cntr_id].rdtgrp) {
>> +			d->cntr_cfg[cntr_id].rdtgrp = rdtgrp;
>> +			d->cntr_cfg[cntr_id].evtid = evtid;
>> +			return cntr_id;
>> +		}
>> +	}
>> +
>> +	return -ENOSPC;
>> +}
>> +
>> +/*
>> + * 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.
>> + *
>> + * Return:
>> + * 0 on success, < 0 on failure.
>> + */
>> +static int rdtgroup_alloc_config_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
>> +				      struct rdtgroup *rdtgrp, enum resctrl_event_id evtid)
> 
> How about rdtgroup_alloc_config_cntr() -> rdtgroup_alloc_assign_cntr()?

Sure.

> 
>> +{
>> +	int cntr_id;
>> +
>> +	/* No action required if the counter is assigned already. */
>> +	cntr_id = mbm_cntr_get(r, d, rdtgrp, evtid);
>> +	if (cntr_id >= 0)
>> +		return 0;
>> +
>> +	cntr_id = mbm_cntr_alloc(r, d, rdtgrp, evtid);
>> +	if (cntr_id <  0) {
>> +		rdt_last_cmd_printf("Unable to allocate counter in domain %d\n",
>> +				    d->hdr.id);
>> +		return cntr_id;
>> +	}
>> +
>> +	resctrl_config_cntr(r, d, evtid, rdtgrp->mon.rmid, rdtgrp->closid,
>> +			    cntr_id, true);
>> +
>> +	return 0;
>> +}
>> +
>> +/*
>> + * rdtgroup_assign_cntr_event() - Assign a hardware counter for the event in
>> + * @mevt to the resctrl group @rdtgrp. Assign counters to all domains if @d is
>> + * NULL; otherwise, assign the counter to the specified domain @d.
>> + *
>> + * If all counters in a domain are already in use, resctrl_alloc_config_cntr()
> 
> resctrl_alloc_config_cntr() needs update to match function name

Sure.

> 
>> + * will fail. The assignment process will abort at the first failure encountered
>> + * during domain traversal, which may result in the event being only partially
>> + * assigned.
>> + *
>> + * Return:
>> + * 0 on success, < 0 on failure.
>> + */
>> +int rdtgroup_assign_cntr_event(struct rdt_mon_domain *d, struct rdtgroup *rdtgrp,
>> +			       struct mon_evt *mevt)
>> +{
>> +	struct rdt_resource *r = resctrl_arch_get_resource(mevt->rid);
>> +	int ret = 0;
>> +
>> +	if (!d) {
>> +		list_for_each_entry(d, &r->mon_domains, hdr.list) {
>> +			ret = rdtgroup_alloc_config_cntr(r, d, rdtgrp, mevt->evtid);
>> +			if (ret)
>> +				return ret;
>> +		}
>> +	} else {
>> +		ret = rdtgroup_alloc_config_cntr(r, d, rdtgrp, mevt->evtid);
>> +	}
>> +
>> +	return ret;
>> +}
> 
> Reinette
> 
> 

-- 
Thanks
Babu Moger

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