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Message-ID: <794cd45701dd52f0a7c3ebda305ff980e761ba35.1749848715.git.babu.moger@amd.com>
Date: Fri, 13 Jun 2025 16:05:04 -0500
From: Babu Moger <babu.moger@....com>
To: <babu.moger@....com>, <corbet@....net>, <tony.luck@...el.com>,
<reinette.chatre@...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: [PATCH v14 20/32] fs/resctrl: Report 'Unassigned' for MBM events in mbm_event mode
When "mbm_event" mode is enabled, a hardware counter must be assigned to
read the event.
Report 'Unassigned' in case the user attempts to read the event without
assigning a hardware counter.
Export mbm_cntr_get() to allow usage from other functions within
fs/resctrl.
Signed-off-by: Babu Moger <babu.moger@....com>
---
v14: Updated the changelog.
Added the code comment for "-ENOENT" when counter is read without assignement.
Removed the references to resctrl_is_mbm_event().
v13: Minor commitlog and user doc update.
Resolved conflicts caused by the recent FS/ARCH code restructure.
The monitor.c/rdtgroup.c files have been split between the FS and ARCH directories.
v12: Updated the documentation for more clarity.
v11: Domain can be NULL with SNC support so moved the unassign check in
rdtgroup_mondata_show().
v10: Moved the code to check the assign state inside mon_event_read().
Fixed few text comments.
v9: Used is_mbm_event() to check the event type.
Minor user documentation update.
v8: Used MBM_EVENT_ARRAY_INDEX to get the index for the MBM event.
Documentation update to make the text generic.
v7: Moved the documentation under "mon_data".
Updated the text little bit.
v6: Added more explaination in the resctrl.rst
Added checks to detect "Unassigned" before reading RMID.
v5: New patch.
---
Documentation/filesystems/resctrl.rst | 8 ++++++++
fs/resctrl/ctrlmondata.c | 19 ++++++++++++++++++-
fs/resctrl/internal.h | 2 ++
fs/resctrl/monitor.c | 4 ++--
4 files changed, 30 insertions(+), 3 deletions(-)
diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index 8a2050098091..18de335e1ff8 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -434,6 +434,14 @@ 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.
+ The "mbm_event" mode offers "num_mbm_cntrs" number of counters and
+ allows users to assign counter IDs to mon_hw_id, event pairs enabling
+ bandwidth monitoring for as long as the counter remains assigned. The
+ hardware will continue tracking the assigned mon_hw_id until the user
+ manually unassigns it, ensuring that event data is not reset during this
+ period. An MBM event returns 'Unassigned' when the event does not have
+ a hardware counter assigned.
+
"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..8a182f506877 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -648,15 +648,32 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
goto out;
}
d = container_of(hdr, struct rdt_mon_domain, hdr);
+
+ /*
+ * Report 'Unassigned' if "mbm_event" mode is enabled and counter
+ * is unassigned.
+ */
+ if (resctrl_arch_mbm_cntr_assign_enabled(r) &&
+ resctrl_is_mbm_event(evtid) &&
+ (mbm_cntr_get(r, d, rdtgrp, evtid) < 0)) {
+ rr.err = -ENOENT;
+ goto checkresult;
+ }
+
mon_event_read(&rr, r, d, rdtgrp, &d->hdr.cpu_mask, evtid, false);
}
checkresult:
-
+ /*
+ * -ENOENT is a special case, set only when "mbm_event" 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 4496c359ac22..4a7130018aa1 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -390,6 +390,8 @@ 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);
+int mbm_cntr_get(struct rdt_resource *r, struct rdt_mon_domain *d,
+ struct rdtgroup *rdtgrp, enum resctrl_event_id evtid);
#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 f2636aea6545..cf7f6a22ea51 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -977,8 +977,8 @@ static void resctrl_config_cntr(struct rdt_resource *r, struct rdt_mon_domain *d
* 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;
--
2.34.1
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