linux-kernel - [PATCH 2/8] resctrl/mon: Split RMID read init from execution

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Message-ID: <20251016144656.74928-3-yonch@yonch.com>
Date: Thu, 16 Oct 2025 09:46:50 -0500
From: Jonathan Perry <yonch@...ch.com>
To: Tony Luck <tony.luck@...el.com>,
	Reinette Chatre <reinette.chatre@...el.com>,
	linux-kernel@...r.kernel.org
Cc: linux-kselftest@...r.kernel.org,
	linux-doc@...r.kernel.org,
	Jonathan Corbet <corbet@....net>,
	James Morse <james.morse@....com>,
	Roman Storozhenko <romeusmeister@...il.com>,
	Jonathan Perry <yonch@...ch.com>
Subject: [PATCH 2/8] resctrl/mon: Split RMID read init from execution

Introduce rmid_read_init() to fill struct rmid_read (resource, domain,
rdtgroup, event id, flags, ci). Change mon_event_read() to accept a
prepared rmid_read and a CPU mask.

Update callers to use rmid_read_init() + mon_event_read().

This prepares reuse from contexts that pre-select the CPU (e.g. the
perf PMU) without duplicating initialization logic.

No functional change intended.

Signed-off-by: Jonathan Perry <yonch@...ch.com>
---
 fs/resctrl/ctrlmondata.c | 40 ++++++++++++++++++++++------------------
 fs/resctrl/internal.h    |  5 +++--
 fs/resctrl/rdtgroup.c    |  6 ++++--
 3 files changed, 29 insertions(+), 22 deletions(-)

diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
index 0d0ef54fc4de..82f8ad2b3053 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -546,28 +546,31 @@ struct rdt_domain_hdr *resctrl_find_domain(struct list_head *h, int id,
 	return NULL;
 }
 
-void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
+void rmid_read_init(struct rmid_read *rr, struct rdt_resource *r,
 		    struct rdt_mon_domain *d, struct rdtgroup *rdtgrp,
-		    cpumask_t *cpumask, int evtid, int first)
+		    int evtid, int first, struct cacheinfo *ci)
 {
-	int cpu;
-
-	/* When picking a CPU from cpu_mask, ensure it can't race with cpuhp */
-	lockdep_assert_cpus_held();
-
-	/*
-	 * Setup the parameters to pass to mon_event_count() to read the data.
-	 */
+	memset(rr, 0, sizeof(*rr));
 	rr->rgrp = rdtgrp;
 	rr->evtid = evtid;
 	rr->r = r;
 	rr->d = d;
 	rr->first = first;
+	rr->ci = ci;
 	if (resctrl_arch_mbm_cntr_assign_enabled(r) &&
-	    resctrl_is_mbm_event(evtid)) {
+	    resctrl_is_mbm_event(evtid))
 		rr->is_mbm_cntr = true;
-	} else {
-		rr->arch_mon_ctx = resctrl_arch_mon_ctx_alloc(r, evtid);
+}
+
+void mon_event_read(struct rmid_read *rr, cpumask_t *cpumask)
+{
+	int cpu;
+
+	/* When picking a CPU from cpu_mask, ensure it can't race with cpuhp */
+	lockdep_assert_cpus_held();
+
+	if (!rr->is_mbm_cntr) {
+		rr->arch_mon_ctx = resctrl_arch_mon_ctx_alloc(rr->r, rr->evtid);
 		if (IS_ERR(rr->arch_mon_ctx)) {
 			rr->err = -EINVAL;
 			return;
@@ -588,7 +591,7 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
 		smp_call_on_cpu(cpu, smp_mon_event_count, rr, false);
 
 	if (rr->arch_mon_ctx)
-		resctrl_arch_mon_ctx_free(r, evtid, rr->arch_mon_ctx);
+		resctrl_arch_mon_ctx_free(rr->r, rr->evtid, rr->arch_mon_ctx);
 }
 
 int rdtgroup_mondata_show(struct seq_file *m, void *arg)
@@ -635,9 +638,9 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
 				ci = get_cpu_cacheinfo_level(cpu, RESCTRL_L3_CACHE);
 				if (!ci)
 					continue;
-				rr.ci = ci;
-				mon_event_read(&rr, r, NULL, rdtgrp,
-					       &ci->shared_cpu_map, evtid, false);
+				rmid_read_init(&rr, r, NULL, rdtgrp,
+					       evtid, false, ci);
+				mon_event_read(&rr, &ci->shared_cpu_map);
 				goto checkresult;
 			}
 		}
@@ -654,7 +657,8 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
 			goto out;
 		}
 		d = container_of(hdr, struct rdt_mon_domain, hdr);
-		mon_event_read(&rr, r, d, rdtgrp, &d->hdr.cpu_mask, evtid, false);
+		rmid_read_init(&rr, r, d, rdtgrp, evtid, false, NULL);
+		mon_event_read(&rr, &d->hdr.cpu_mask);
 	}
 
 checkresult:
diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index 63fb4d6c21a7..dcc0b7bea3ac 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -363,9 +363,10 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg);
 int rdtgroup_mondata_open(struct kernfs_open_file *of);
 void rdtgroup_mondata_release(struct kernfs_open_file *of);
 
-void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
+void rmid_read_init(struct rmid_read *rr, struct rdt_resource *r,
 		    struct rdt_mon_domain *d, struct rdtgroup *rdtgrp,
-		    cpumask_t *cpumask, int evtid, int first);
+		    int evtid, int first, struct cacheinfo *ci);
+void mon_event_read(struct rmid_read *rr, cpumask_t *cpumask);
 
 int resctrl_mon_resource_init(void);
 
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 17b61dcfad07..34337abe5345 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -3235,8 +3235,10 @@ static int mon_add_all_files(struct kernfs_node *kn, struct rdt_mon_domain *d,
 		if (ret)
 			return ret;
 
-		if (!do_sum && resctrl_is_mbm_event(mevt->evtid))
-			mon_event_read(&rr, r, d, prgrp, &d->hdr.cpu_mask, mevt->evtid, true);
+		if (!do_sum && resctrl_is_mbm_event(mevt->evtid)) {
+			rmid_read_init(&rr, r, d, prgrp, mevt->evtid, true, NULL);
+			mon_event_read(&rr, &d->hdr.cpu_mask);
+		}
 	}
 
 	return 0;