[PATCH v3 19/26] x86/resctrl: Sanity check telemetry RMID values

Tony Luck
2025-04-07T23:40:59Z

There are three values of interest:
1) The number of RMIDs supported by the CPU core. This is enumerated by
CPUID leaf 0xF. Linux saves the value in boot_cpu_data.x86_cache_max_rmid.
2) The number of counter registers in each telemetry region. This is
described in the XML file for the region. Linux hard codes it into
the struct telem_entry..num_rmids field.
3) The maximum number of RMIDs that can be tracked simultaneously for
a telemetry region. This is provided in the structures received from
the intel_pmt_get_regions_by_feature() calls.

Print appropriate warnings if these values do not match.

TODO: Need a better UI. The number of implemented counters can be
different per telemetry region.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
arch/x86/kernel/cpu/resctrl/intel_aet.c | 31 +++++++++++++++++++++++++
1 file changed, 31 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/intel_aet.c b/arch/x86/kernel/cpu/resctrl/intel_aet.c
index 67a1245858dc..0bcbac326bee 100644
--- a/arch/x86/kernel/cpu/resctrl/intel_aet.c
+++ b/arch/x86/kernel/cpu/resctrl/intel_aet.c
@@ -13,6 +13,7 @@

#include <linux/cpu.h>
#include <linux/cleanup.h>
+#include <linux/minmax.h>
#include "fake_intel_aet_features.h"
#include <linux/intel_vsec.h>
#include <linux/resctrl.h>
@@ -51,6 +52,7 @@ struct pmt_event {
* @last_overflow_tstamp_off: Offset of overflow timestamp
* @last_update_tstamp_off: Offset of last update timestamp
* @active: Marks this group as active on this system
+ * @rmid_warned: Set to stop multiple rmid sanity warnings
* @num_events: Size of @evts array
* @evts: Telemetry events in this group
*/
@@ -63,6 +65,7 @@ struct telem_entry {
int last_overflow_tstamp_off;
int last_update_tstamp_off;
bool active;
+ bool rmid_warned;
int num_events;
struct pmt_event evts[];
};
@@ -84,6 +87,33 @@ static struct telem_entry *telem_entry[] = {
NULL
};

+static void rmid_sanity_check(struct telemetry_region *tr, struct telem_entry *tentry)
+{
+ struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_PERF_PKG].r_resctrl;
+ int system_rmids = boot_cpu_data.x86_cache_max_rmid + 1;
+
+ if (tentry->rmid_warned)
+ return;
+
+ if (tentry->num_rmids != system_rmids) {
+ pr_info("Telemetry region %s has %d RMIDs system supports %d\n",
+ tentry->name, tentry->num_rmids, system_rmids);
+ tentry->rmid_warned = true;
+ }
+
+ if (tr->num_rmids < tentry->num_rmids) {
+ pr_info("Telemetry region %s only supports %d simultaneous RMIDS\n",
+ tentry->name, tr->num_rmids);
+ tentry->rmid_warned = true;
+ }
+
+ /* info/PKG_PERF_MON/num_rmids reports number of guaranteed counters */
+ if (!r->num_rmid)
+ r->num_rmid = tr->num_rmids;
+ else
+ r->num_rmid = min((u32)r->num_rmid, tr->num_rmids);
+}
+
/*
* Scan a feature group looking for guids recognized
* and update the per-package counts of known groups.
@@ -109,6 +139,7 @@ static bool count_events(struct pkg_info *pkg, int max_pkgs, struct pmt_feature_
pr_warn_once("MMIO region for guid 0x%x too small\n", tr->guid);
continue;
}
+ rmid_sanity_check(tr, *tentry);
found = true;
(*tentry)->active = true;
pkg[tr->plat_info.package_id].count++;
--
2.48.1