Message-ID: <70ef9637d73825ee5e7409ab04df1039dec0873c.1752013061.git.babu.moger@amd.com>
Date: Tue, 8 Jul 2025 17:17:26 -0500
From: Babu Moger <babu.moger@....com>
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Subject: [PATCH v15 17/34] fs/resctrl: Add the functionality to assign MBM events

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>
---
v15: Updated the changelog.
     Added the check !r->mon.mbm_cntr_assignable in mbm_cntr_get() to return error.
     Removed the check to verify evt_cfg in the domain as it is not required anymore.
     https://lore.kernel.org/lkml/887bad33-7f4a-4b6d-95a7-fdfe0451f42b@intel.com/
     Return success if the counter is already assigned.
     Rename resctrl_assign_cntr_event() -> rdtgroup_assign_cntr_event().
     Removed the parameter struct rdt_resource. It can be obtained from mevt->rid.

v14: Updated the changelog little bit.
     Updated the code documentation for mbm_cntr_alloc() and  mbm_cntr_get().
     Passed struct mon_evt to resctrl_assign_cntr_event() that way to avoid
     back and forth calls to get event details.
     Updated the code documentation about the failure when counters are exhasted.
     Changed subject line to fs/resctrl.

v13: Updated changelog.
     Changed resctrl_arch_config_cntr() to return void instead of int.
     Just passing evtid is to resctrl_alloc_config_cntr() and
     resctrl_assign_cntr_event(). Event configuration value can be easily
     obtained from mon_evt list.
     Introduced new function mbm_get_mon_event() to get event configuration value.
     Added prototype descriptions to mbm_cntr_get() and mbm_cntr_alloc().
     Resolved conflicts caused by the recent FS/ARCH code restructure.
     The files monitor.c/rdtgroup.c have been split between FS and ARCH directories.

v12: Fixed typo in the subjest line.
     Replaced several counters with "num_mbm_cntrs" counters.
     Changed the check in resctrl_alloc_config_cntr() to reduce the indentation.
     Fixed the handling error on first failure.
     Added domain id and event id on failure.
     Fixed the return error override.
     Added new parameter event configuration (evt_cfg) to get the event configuration
     from user space.

v11: Patch changed again quite a bit.
     Moved the functions to monitor.c.
     Renamed rdtgroup_assign_cntr_event() to resctrl_assign_cntr_event().
     Refactored the resctrl_assign_cntr_event().
     Added functionality to exit on the first error during assignment.
     Simplified mbm_cntr_free().
     Removed the function mbm_cntr_assigned(). Will be using mbm_cntr_get() to
     figure out if the counter is assigned or not.
     Updated commit message and code comments.

v10: Patch changed completely.
     Counters are managed at the domain based on the discussion.
     https://lore.kernel.org/lkml/CALPaoCj+zWq1vkHVbXYP0znJbe6Ke3PXPWjtri5AFgD9cQDCUg@mail.gmail.com/
     Reset non-architectural MBM state.
     Commit message update.

v9: Introduced new function resctrl_config_cntr to assign the counter, update
    the bitmap and reset the architectural state.
    Taken care of error handling(freeing the counter) when assignment fails.
    Moved mbm_cntr_assigned_to_domain here as it used in this patch.
    Minor text changes.

v8: Renamed rdtgroup_assign_cntr() to rdtgroup_assign_cntr_event().
    Added the code to return the error if rdtgroup_assign_cntr_event fails.
    Moved definition of MBM_EVENT_ARRAY_INDEX to resctrl/internal.h.
    Updated typo in the comments.

v7: New patch. Moved all the FS code here.
    Merged rdtgroup_assign_cntr and rdtgroup_alloc_cntr.
    Adde new #define MBM_EVENT_ARRAY_INDEX.
---
 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.
+ */
+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)
+{
+	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()
+ * 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;
+}
-- 
2.34.1

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