x86/resctrl: Fill out rmid_read structure for smp_call*() to read a counter

mon_event_read() fills out most fields of the struct rmid_read that is passed
via an smp_call*() function to a CPU that is part of the correct domain to
read the monitor counters.

With Sub-NUMA Cluster (SNC) mode there are now two cases to handle:

1) Reading a file that returns a value for a single domain.
   + Choose the CPU to execute from the domain cpu_mask

2) Reading a file that must sum across domains sharing an L3 cache
   instance.
   + Indicate to called code that a sum is needed by passing a NULL
     rdt_mon_domain pointer.
   + Choose the CPU from the L3 shared_cpu_map.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Link: https://lore.kernel.org/r/20240628215619.76401-16-tony.luck@intel.com

Author: aegl

arch/x86/kernel/cpu/resctrl/ctrlmondata.c

@@ -515,7 +515,7 @@ static int smp_mon_event_count(void *arg)
 
 void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
 		    struct rdt_mon_domain *d, struct rdtgroup *rdtgrp,
-		    int evtid, int first)
+		    cpumask_t *cpumask, int evtid, int first)
 {
 	int cpu;
 
@@ -536,7 +536,7 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
 		return;
 	}
 
-	cpu = cpumask_any_housekeeping(&d->hdr.cpu_mask, RESCTRL_PICK_ANY_CPU);
+	cpu = cpumask_any_housekeeping(cpumask, RESCTRL_PICK_ANY_CPU);
 
 	/*
 	 * cpumask_any_housekeeping() prefers housekeeping CPUs, but
@@ -545,7 +545,7 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
 	 * counters on some platforms if its called in IRQ context.
 	 */
 	if (tick_nohz_full_cpu(cpu))
-		smp_call_function_any(&d->hdr.cpu_mask, mon_event_count, rr, 1);
+		smp_call_function_any(cpumask, mon_event_count, rr, 1);
 	else
 		smp_call_on_cpu(cpu, smp_mon_event_count, rr, false);
 
@@ -574,16 +574,40 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
 	resid = md.u.rid;
 	domid = md.u.domid;
 	evtid = md.u.evtid;
-
 	r = &rdt_resources_all[resid].r_resctrl;
-	hdr = rdt_find_domain(&r->mon_domains, domid, NULL);
-	if (!hdr || WARN_ON_ONCE(hdr->type != RESCTRL_MON_DOMAIN)) {
+
+	if (md.u.sum) {
+		/*
+		 * This file requires summing across all domains that share
+		 * the L3 cache id that was provided in the "domid" field of the
+		 * mon_data_bits union. Search all domains in the resource for
+		 * one that matches this cache id.
+		 */
+		list_for_each_entry(d, &r->mon_domains, hdr.list) {
+			if (d->ci->id == domid) {
+				rr.ci = d->ci;
+				mon_event_read(&rr, r, NULL, rdtgrp,
+					       &d->ci->shared_cpu_map, evtid, false);
+				goto checkresult;
+			}
+		}
 		ret = -ENOENT;
 		goto out;
+	} else {
+		/*
+		 * This file provides data from a single domain. Search
+		 * the resource to find the domain with "domid".
+		 */
+		hdr = rdt_find_domain(&r->mon_domains, domid, NULL);
+		if (!hdr || WARN_ON_ONCE(hdr->type != RESCTRL_MON_DOMAIN)) {
+			ret = -ENOENT;
+			goto out;
+		}
+		d = container_of(hdr, struct rdt_mon_domain, hdr);
+		mon_event_read(&rr, r, d, rdtgrp, &d->hdr.cpu_mask, evtid, false);
 	}
-	d = container_of(hdr, struct rdt_mon_domain, hdr);
 
-	mon_event_read(&rr, r, d, rdtgrp, evtid, false);
+checkresult:
 
 	if (rr.err == -EIO)
 		seq_puts(m, "Error\n");

arch/x86/kernel/cpu/resctrl/internal.h

@@ -632,7 +632,7 @@ void mon_event_count(void *info);
 int rdtgroup_mondata_show(struct seq_file *m, void *arg);
 void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
 		    struct rdt_mon_domain *d, struct rdtgroup *rdtgrp,
-		    int evtid, int first);
+		    cpumask_t *cpumask, int evtid, int first);
 void mbm_setup_overflow_handler(struct rdt_mon_domain *dom,
 				unsigned long delay_ms,
 				int exclude_cpu);

arch/x86/kernel/cpu/resctrl/rdtgroup.c

@@ -3070,7 +3070,7 @@ static int mon_add_all_files(struct kernfs_node *kn, struct rdt_mon_domain *d,
 			return ret;
 
 		if (!do_sum && is_mbm_event(mevt->evtid))
-			mon_event_read(&rr, r, d, prgrp, mevt->evtid, true);
+			mon_event_read(&rr, r, d, prgrp, &d->hdr.cpu_mask, mevt->evtid, true);
 	}
 
 	return 0;