[PATCH v18 15/17] x86/resctrl: Fix RMID reading sanity check for Sub-NUMA (SNC) mode

[Tony Luck]

The sanity check that RMIDs are being read from a CPU listed in the
the cpu_mask for the domain is incorrect when summing across multiple
SNC domains. It is safe to read the RMID from any CPU that shares the
same L3 cache instance.

Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
---
 arch/x86/kernel/cpu/resctrl/monitor.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 668d2fdf58cd..e4b92c7af71d 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -15,6 +15,7 @@
  * Software Developer Manual June 2016, volume 3, section 17.17.
  */
 
+#include <linux/cacheinfo.h>
 #include <linux/cpu.h>
 #include <linux/module.h>
 #include <linux/sizes.h>
@@ -281,8 +282,18 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_mon_domain *d,
 
 	resctrl_arch_rmid_read_context_check();
 
-	if (!cpumask_test_cpu(smp_processor_id(), &d->hdr.cpu_mask))
-		return -EINVAL;
+	if (r->mon_scope == r->mon_display_scope) {
+		if (!cpumask_test_cpu(smp_processor_id(), &d->hdr.cpu_mask))
+			return -EINVAL;
+	} else {
+		/*
+		 * SNC: OK to read events on any CPU sharing same L3
+		 * cache instance.
+		 */
+		if (d->display_id != get_cpu_cacheinfo_id(smp_processor_id(),
+							  r->mon_display_scope))
+			return -EINVAL;
+	}
 
 	ret = __rmid_read(rmid, eventid, &msr_val);
 	if (ret)
-- 
2.44.0