resctrl assumes that monitor events can only be read from a CPU in the
cpumask_t set of each domain.  This is true for x86 events accessed
with an MSR interface, but may not be true for other access methods such
as MMIO.

Add a flag to struct mon_evt, settable by architecture code, to indicate
there are no restrictions on which CPU can read that event.

Bypass all the smp_call*() code for events that can be read on any CPU
and call mon_event_count() directly from mon_event_read().

Simplify CPU checking in __mon_event_count() with a helper.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
 include/linux/resctrl.h            |  2 +-
 fs/resctrl/internal.h              |  2 ++
 arch/x86/kernel/cpu/resctrl/core.c |  6 ++---
 fs/resctrl/ctrlmondata.c           |  6 +++++
 fs/resctrl/monitor.c               | 43 ++++++++++++++++++++++--------
 5 files changed, 44 insertions(+), 15 deletions(-)

diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 66569662efee..22edd8d131d8 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -409,7 +409,7 @@ u32 resctrl_arch_get_num_closid(struct rdt_resource *r);
 u32 resctrl_arch_system_num_rmid_idx(void);
 int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid);
 
-void resctrl_enable_mon_event(enum resctrl_event_id eventid);
+void resctrl_enable_mon_event(enum resctrl_event_id eventid, bool any_cpu);
 
 bool resctrl_is_mon_event_enabled(enum resctrl_event_id eventid);
 
diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index 12a2ab7e3c9b..40b76eaa33d0 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -61,6 +61,7 @@ static inline struct rdt_fs_context *rdt_fc2context(struct fs_context *fc)
  *			READS_TO_REMOTE_MEM) being tracked by @evtid.
  *			Only valid if @evtid is an MBM event.
  * @configurable:	true if the event is configurable
+ * @any_cpu:		true if the event can be read from any CPU
  * @enabled:		true if the event is enabled
  */
 struct mon_evt {
@@ -69,6 +70,7 @@ struct mon_evt {
 	char			*name;
 	u32			evt_cfg;
 	bool			configurable;
+	bool			any_cpu;
 	bool			enabled;
 };
 
diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 4762790c6e62..8db941fef7a0 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -889,15 +889,15 @@ static __init bool get_rdt_mon_resources(void)
 	bool ret = false;
 
 	if (rdt_cpu_has(X86_FEATURE_CQM_OCCUP_LLC)) {
-		resctrl_enable_mon_event(QOS_L3_OCCUP_EVENT_ID);
+		resctrl_enable_mon_event(QOS_L3_OCCUP_EVENT_ID, false);
 		ret = true;
 	}
 	if (rdt_cpu_has(X86_FEATURE_CQM_MBM_TOTAL)) {
-		resctrl_enable_mon_event(QOS_L3_MBM_TOTAL_EVENT_ID);
+		resctrl_enable_mon_event(QOS_L3_MBM_TOTAL_EVENT_ID, false);
 		ret = true;
 	}
 	if (rdt_cpu_has(X86_FEATURE_CQM_MBM_LOCAL)) {
-		resctrl_enable_mon_event(QOS_L3_MBM_LOCAL_EVENT_ID);
+		resctrl_enable_mon_event(QOS_L3_MBM_LOCAL_EVENT_ID, false);
 		ret = true;
 	}
 	if (rdt_cpu_has(X86_FEATURE_ABMC))
diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
index 77602563cb1f..fbf55e61445c 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -574,6 +574,11 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
 		}
 	}
 
+	if (evt->any_cpu) {
+		mon_event_count(rr);
+		goto out_ctx_free;
+	}
+
 	cpu = cpumask_any_housekeeping(cpumask, RESCTRL_PICK_ANY_CPU);
 
 	/*
@@ -587,6 +592,7 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
 	else
 		smp_call_on_cpu(cpu, smp_mon_event_count, rr, false);
 
+out_ctx_free:
 	if (rr->arch_mon_ctx)
 		resctrl_arch_mon_ctx_free(r, evt->evtid, rr->arch_mon_ctx);
 }
diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
index ee08ffbacc2b..6f8a9b5a2f6b 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -413,9 +413,33 @@ static void mbm_cntr_free(struct rdt_l3_mon_domain *d, int cntr_id)
 	memset(&d->cntr_cfg[cntr_id], 0, sizeof(*d->cntr_cfg));
 }
 
+/*
+ * Called from preemptible context via a direct call of mon_event_count() for
+ * events that can be read on any CPU.
+ * Called from preemptible but non-migratable process context (mon_event_count()
+ * via smp_call_on_cpu()) OR non-preemptible context (mon_event_count() via
+ * smp_call_function_any()) for events that need to be read on a specific CPU.
+ */
+static bool cpu_on_correct_domain(struct rmid_read *rr)
+{
+	int cpu;
+
+	/* Any CPU is OK for this event */
+	if (rr->evt->any_cpu)
+		return true;
+
+	cpu = smp_processor_id();
+
+	/* Single domain. Must be on a CPU in that domain. */
+	if (rr->hdr)
+		return cpumask_test_cpu(cpu, &rr->hdr->cpu_mask);
+
+	/* Summing domains that share a cache, must be on a CPU for that cache. */
+	return cpumask_test_cpu(cpu, &rr->ci->shared_cpu_map);
+}
+
 static int __mon_event_count(struct rdtgroup *rdtgrp, struct rmid_read *rr)
 {
-	int cpu = smp_processor_id();
 	u32 closid = rdtgrp->closid;
 	u32 rmid = rdtgrp->mon.rmid;
 	struct rdt_l3_mon_domain *d;
@@ -424,6 +448,9 @@ static int __mon_event_count(struct rdtgroup *rdtgrp, struct rmid_read *rr)
 	int err, ret;
 	u64 tval = 0;
 
+	if (!cpu_on_correct_domain(rr))
+		return -EINVAL;
+
 	if (!domain_header_is_valid(rr->hdr, RESCTRL_MON_DOMAIN, RDT_RESOURCE_L3))
 		return -EINVAL;
 	d = container_of(rr->hdr, struct rdt_l3_mon_domain, hdr);
@@ -448,9 +475,6 @@ static int __mon_event_count(struct rdtgroup *rdtgrp, struct rmid_read *rr)
 	}
 
 	if (rr->hdr) {
-		/* Reading a single domain, must be on a CPU in that domain. */
-		if (!cpumask_test_cpu(cpu, &rr->hdr->cpu_mask))
-			return -EINVAL;
 		if (rr->is_mbm_cntr)
 			rr->err = resctrl_arch_cntr_read(rr->r, rr->hdr, closid, rmid, cntr_id,
 							 rr->evt->evtid, &tval);
@@ -465,10 +489,6 @@ static int __mon_event_count(struct rdtgroup *rdtgrp, struct rmid_read *rr)
 		return 0;
 	}
 
-	/* Summing domains that share a cache, must be on a CPU for that cache. */
-	if (!cpumask_test_cpu(cpu, &rr->ci->shared_cpu_map))
-		return -EINVAL;
-
 	/*
 	 * Legacy files must report the sum of an event across all
 	 * domains that share the same L3 cache instance.
@@ -957,7 +977,7 @@ struct mon_evt mon_event_all[QOS_NUM_EVENTS] = {
 	},
 };
 
-void resctrl_enable_mon_event(enum resctrl_event_id eventid)
+void resctrl_enable_mon_event(enum resctrl_event_id eventid, bool any_cpu)
 {
 	if (WARN_ON_ONCE(eventid < QOS_FIRST_EVENT || eventid >= QOS_NUM_EVENTS))
 		return;
@@ -966,6 +986,7 @@ void resctrl_enable_mon_event(enum resctrl_event_id eventid)
 		return;
 	}
 
+	mon_event_all[eventid].any_cpu = any_cpu;
 	mon_event_all[eventid].enabled = true;
 }
 
@@ -1791,9 +1812,9 @@ int resctrl_l3_mon_resource_init(void)
 
 	if (r->mon.mbm_cntr_assignable) {
 		if (!resctrl_is_mon_event_enabled(QOS_L3_MBM_TOTAL_EVENT_ID))
-			resctrl_enable_mon_event(QOS_L3_MBM_TOTAL_EVENT_ID);
+			resctrl_enable_mon_event(QOS_L3_MBM_TOTAL_EVENT_ID, false);
 		if (!resctrl_is_mon_event_enabled(QOS_L3_MBM_LOCAL_EVENT_ID))
-			resctrl_enable_mon_event(QOS_L3_MBM_LOCAL_EVENT_ID);
+			resctrl_enable_mon_event(QOS_L3_MBM_LOCAL_EVENT_ID, false);
 		mon_event_all[QOS_L3_MBM_TOTAL_EVENT_ID].evt_cfg = r->mon.mbm_cfg_mask;
 		mon_event_all[QOS_L3_MBM_LOCAL_EVENT_ID].evt_cfg = r->mon.mbm_cfg_mask &
 								   (READS_TO_LOCAL_MEM |
-- 
2.51.0