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

Tony Luck
2024-05-15T22:23:44Z

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@intel.com>
---
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