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Message-ID: <26db5cff-dc25-417e-bac2-e05584e8f987@intel.com>
Date: Wed, 30 Jul 2025 13:03:17 -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 v16 23/34] fs/resctrl: Support counter read/reset with
mbm_event assignment mode
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
>
> 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.
> * @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
> #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?
> + 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?
Reinette
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