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Message-ID: <62c5e15f-8dc6-4ceb-8bd1-f1389ed8dffa@amd.com>
Date: Thu, 7 Aug 2025 21:20:15 -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 v16 23/34] fs/resctrl: Support counter read/reset with
mbm_event assignment mode
Hi Reinette,
On 7/30/25 15:03, Reinette Chatre wrote:
> Hi Babu,
>
> On 7/25/25 11:29 AM, Babu Moger wrote:
>> When "mbm_event" counter assignment mode is enabled, the architecture
>> requires a counter ID to read the event data.
>>
>> Introduce an is_mbm_cntr field in struct rmid_read to indicate whether
>> counter assignment mode is in use.
>>
>> Update the logic to call resctrl_arch_cntr_read() and
>> resctrl_arch_reset_cntr() when the assignment mode is active. Report
>> 'Unassigned' in case the user attempts to read the event without assigning
>> a hardware counter.
>>
>> Declare mbm_cntr_get() in fs/resctrl/internal.h to make it accessible to
>> other functions within fs/resctrl.
>
>>>From what I can tell this is not needed by this patch. It is also a hint that
> there may be some monitoring specific code outside of monitor.c. Looks like this
> is done to support later patch #29 "fs/resctrl: Introduce mbm_L3_assignments to
> list assignments in a group" where mbm_L3_assignments_show() should rather
> be in monitor.c
Yes. Will move all these to monitor.c.
>
>>
>> Suggested-by: Reinette Chatre <reinette.chatre@...el.com>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
> ...
>
>> ---
>> Documentation/filesystems/resctrl.rst | 6 ++++
>> fs/resctrl/ctrlmondata.c | 22 +++++++++---
>> fs/resctrl/internal.h | 5 +++
>> fs/resctrl/monitor.c | 52 ++++++++++++++++++++-------
>> 4 files changed, 67 insertions(+), 18 deletions(-)
>>
>> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
>> index 446736dbd97f..4c24c5f3f4c1 100644
>> --- a/Documentation/filesystems/resctrl.rst
>> +++ b/Documentation/filesystems/resctrl.rst
>> @@ -434,6 +434,12 @@ When monitoring is enabled all MON groups will also contain:
>> for the L3 cache they occupy). These are named "mon_sub_L3_YY"
>> where "YY" is the node number.
>>
>> + When the 'mbm_event' counter assignment mode is enabled, reading
>> + an MBM event of a MON group returns 'Unassigned' if no hardware
>> + counter is assigned to it. For CTRL_MON groups, 'Unassigned' is
>> + returned if the MBM event does not have an assigned counter in the
>> + CTRL_MON group nor in any of its associated MON groups.
>> +
>> "mon_hw_id":
>> Available only with debug option. The identifier used by hardware
>> for the monitor group. On x86 this is the RMID.
>> diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
>> index ad7ffc6acf13..31787ce6ec91 100644
>> --- a/fs/resctrl/ctrlmondata.c
>> +++ b/fs/resctrl/ctrlmondata.c
>> @@ -563,10 +563,15 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
>> rr->r = r;
>> rr->d = d;
>> rr->first = first;
>> - rr->arch_mon_ctx = resctrl_arch_mon_ctx_alloc(r, evtid);
>> - if (IS_ERR(rr->arch_mon_ctx)) {
>> - rr->err = -EINVAL;
>> - return;
>> + if (resctrl_arch_mbm_cntr_assign_enabled(r) &&
>> + resctrl_is_mbm_event(evtid)) {
>> + rr->is_mbm_cntr = true;
>> + } else {
>> + rr->arch_mon_ctx = resctrl_arch_mon_ctx_alloc(r, evtid);
>> + if (IS_ERR(rr->arch_mon_ctx)) {
>> + rr->err = -EINVAL;
>> + return;
>> + }
>> }
>>
>> cpu = cpumask_any_housekeeping(cpumask, RESCTRL_PICK_ANY_CPU);
>> @@ -582,7 +587,8 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
>> else
>> smp_call_on_cpu(cpu, smp_mon_event_count, rr, false);
>>
>> - resctrl_arch_mon_ctx_free(r, evtid, rr->arch_mon_ctx);
>> + if (rr->arch_mon_ctx)
>> + resctrl_arch_mon_ctx_free(r, evtid, rr->arch_mon_ctx);
>> }
>>
>> int rdtgroup_mondata_show(struct seq_file *m, void *arg)
>> @@ -653,10 +659,16 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
>>
>> checkresult:
>>
>> + /*
>> + * -ENOENT is a special case, set only when "mbm_event" counter assignment
>> + * mode is enabled and no counter has been assigned.
>> + */
>> if (rr.err == -EIO)
>> seq_puts(m, "Error\n");
>> else if (rr.err == -EINVAL)
>> seq_puts(m, "Unavailable\n");
>> + else if (rr.err == -ENOENT)
>> + seq_puts(m, "Unassigned\n");
>> else
>> seq_printf(m, "%llu\n", rr.val);
>>
>> diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
>> index 216588842444..eeee83a5067a 100644
>> --- a/fs/resctrl/internal.h
>> +++ b/fs/resctrl/internal.h
>> @@ -110,6 +110,8 @@ struct mon_data {
>> * domains in @r sharing L3 @ci.id
>> * @evtid: Which monitor event to read.
>> * @first: Initialize MBM counter when true.
>> + * @is_mbm_cntr: Is the counter valid? true if "mbm_event" counter assignment mode is
>> + * enabled and it is an MBM event.
>
> Since a counter may not be assigned to event being read I do not believe that "Is the counter
> valid?" is accurate and should rather be dropped. Rest of text looks accurate to me.
Sure.
>
>> * @ci_id: Cacheinfo id for L3. Only set when @d is NULL. Used when summing domains.
>> * @err: Error encountered when reading counter.
>> * @val: Returned value of event counter. If @rgrp is a parent resource group,
>> @@ -124,6 +126,7 @@ struct rmid_read {
>> struct rdt_mon_domain *d;
>> enum resctrl_event_id evtid;
>> bool first;
>> + bool is_mbm_cntr;
>> unsigned int ci_id;
>> int err;
>> u64 val;
>> @@ -391,6 +394,8 @@ int rdtgroup_assign_cntr_event(struct rdt_mon_domain *d, struct rdtgroup *rdtgrp
>> struct mon_evt *mevt);
>> void rdtgroup_unassign_cntr_event(struct rdt_mon_domain *d, struct rdtgroup *rdtgrp,
>> struct mon_evt *mevt);
>> +int mbm_cntr_get(struct rdt_resource *r, struct rdt_mon_domain *d,
>> + struct rdtgroup *rdtgrp, enum resctrl_event_id evtid);
>>
>
> Not necessary? mbm_cntr_get() can remain internal to monitor.c
Yes. Not necessary.
>
>> #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 070965d45770..a8b53b0ad0b7 100644
>> --- a/fs/resctrl/monitor.c
>> +++ b/fs/resctrl/monitor.c
>> @@ -362,13 +362,25 @@ static int __mon_event_count(struct rdtgroup *rdtgrp, struct rmid_read *rr)
>> u32 closid = rdtgrp->closid;
>> u32 rmid = rdtgrp->mon.rmid;
>> struct rdt_mon_domain *d;
>> + int cntr_id = -ENOENT;
>> struct cacheinfo *ci;
>> struct mbm_state *m;
>> int err, ret;
>> u64 tval = 0;
>>
>> + if (rr->is_mbm_cntr) {
>> + cntr_id = mbm_cntr_get(rr->r, rr->d, rdtgrp, rr->evtid);
>> + if (cntr_id < 0) {
>> + rr->err = -ENOENT;
>> + return -EINVAL;
>> + }
>> + }
>> +
>> if (rr->first) {
>> - resctrl_arch_reset_rmid(rr->r, rr->d, closid, rmid, rr->evtid);
>> + if (rr->is_mbm_cntr)
>> + resctrl_arch_reset_cntr(rr->r, rr->d, closid, rmid, cntr_id, rr->evtid);
>> + else
>> + resctrl_arch_reset_rmid(rr->r, rr->d, closid, rmid, rr->evtid);
>> m = get_mbm_state(rr->d, closid, rmid, rr->evtid);
>> if (m)
>> memset(m, 0, sizeof(struct mbm_state));
>> @@ -379,8 +391,12 @@ static int __mon_event_count(struct rdtgroup *rdtgrp, struct rmid_read *rr)
>> /* Reading a single domain, must be on a CPU in that domain. */
>> if (!cpumask_test_cpu(cpu, &rr->d->hdr.cpu_mask))
>> return -EINVAL;
>> - rr->err = resctrl_arch_rmid_read(rr->r, rr->d, closid, rmid,
>> - rr->evtid, &tval, rr->arch_mon_ctx);
>> + if (rr->is_mbm_cntr)
>> + rr->err = resctrl_arch_cntr_read(rr->r, rr->d, closid, rmid, cntr_id,
>> + rr->evtid, &tval);
>> + else
>> + rr->err = resctrl_arch_rmid_read(rr->r, rr->d, closid, rmid,
>> + rr->evtid, &tval, rr->arch_mon_ctx);
>> if (rr->err)
>> return rr->err;
>>
>> @@ -405,8 +421,12 @@ static int __mon_event_count(struct rdtgroup *rdtgrp, struct rmid_read *rr)
>> list_for_each_entry(d, &rr->r->mon_domains, hdr.list) {
>> if (d->ci_id != rr->ci_id)
>> continue;
>> - err = resctrl_arch_rmid_read(rr->r, d, closid, rmid,
>> - rr->evtid, &tval, rr->arch_mon_ctx);
>> + if (rr->is_mbm_cntr)
>> + err = resctrl_arch_cntr_read(rr->r, d, closid, rmid, cntr_id,
>> + rr->evtid, &tval);
>> + else
>> + err = resctrl_arch_rmid_read(rr->r, d, closid, rmid,
>> + rr->evtid, &tval, rr->arch_mon_ctx);
>> if (!err) {
>> rr->val += tval;
>> ret = 0;
>> @@ -613,11 +633,16 @@ static void mbm_update_one_event(struct rdt_resource *r, struct rdt_mon_domain *
>> rr.r = r;
>> rr.d = d;
>> rr.evtid = evtid;
>> - rr.arch_mon_ctx = resctrl_arch_mon_ctx_alloc(rr.r, rr.evtid);
>> - if (IS_ERR(rr.arch_mon_ctx)) {
>> - pr_warn_ratelimited("Failed to allocate monitor context: %ld",
>> - PTR_ERR(rr.arch_mon_ctx));
>> - return;
>> + if (resctrl_arch_mbm_cntr_assign_enabled(r) &&
>> + resctrl_arch_mbm_cntr_assign_enabled(r)) {
>
> Duplicate check?
Yes.
>
>> + rr.is_mbm_cntr = true;
>> + } else {
>> + rr.arch_mon_ctx = resctrl_arch_mon_ctx_alloc(rr.r, rr.evtid);
>> + if (IS_ERR(rr.arch_mon_ctx)) {
>> + pr_warn_ratelimited("Failed to allocate monitor context: %ld",
>> + PTR_ERR(rr.arch_mon_ctx));
>> + return;
>> + }
>> }
>>
>> __mon_event_count(rdtgrp, &rr);
>> @@ -629,7 +654,8 @@ static void mbm_update_one_event(struct rdt_resource *r, struct rdt_mon_domain *
>> if (is_mba_sc(NULL))
>> mbm_bw_count(rdtgrp, &rr);
>>
>> - resctrl_arch_mon_ctx_free(rr.r, rr.evtid, rr.arch_mon_ctx);
>> + if (rr.arch_mon_ctx)
>> + resctrl_arch_mon_ctx_free(rr.r, rr.evtid, rr.arch_mon_ctx);
>> }
>>
>> static void mbm_update(struct rdt_resource *r, struct rdt_mon_domain *d,
>> @@ -983,8 +1009,8 @@ static void rdtgroup_assign_cntr(struct rdt_resource *r, struct rdt_mon_domain *
>> * 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 mbm_cntr_get(struct rdt_resource *r, struct rdt_mon_domain *d,
>> + struct rdtgroup *rdtgrp, enum resctrl_event_id evtid)
>> {
>> int cntr_id;
>>
>
> Not necessary?
>
Yes.
--
Thanks
Babu Moger
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