Re: [PATCH v14 19/32] x86/resctrl: Find and enable usable telemetry events

Reinette Chatre
2025-12-02T16:21:20Z

Hi Tony,

On 11/24/25 10:53 AM, Tony Luck wrote:
> Every event group has a private copy of the data of all telemetry event
> aggregators (aka "telemetry regions") tracking its feature type. Included
> may be regions that have the same feature type but tracking different guid
> from the event group's.
>
> Traverse the event group's telemetry region data and mark all regions that
> are not usable by the event group as unusable by clearing those regions'
> MMIO addresses. A region is considered unusable if:
> 1) guid does not match the guid of the event group.
> 2) Package ID is invalid.
> 3) The enumerated size of the MMIO region does not match the expected
> value from the XML description file.
>
> Hereafter any telemetry region with an MMIO address is considered valid for
> the event group it is associated with.
>
> Enable all the event group's events as long as there is at least one usable
> region from where data for its events can be read.

Changelog does not mention the "skipped_events" handling added in this version.

>
> Note that it is architecturally possible that some telemetry events are
> only supported by a subset of the packages in the system. It is not expected
> that systems will ever do this. If they do the user will see event files in
> resctrl that always return "Unavailable".
>
> Signed-off-by: Tony Luck <tony.luck@intel.com>
> ---
> include/linux/resctrl.h | 2 +-
> arch/x86/kernel/cpu/resctrl/intel_aet.c | 62 ++++++++++++++++++++++++-
> fs/resctrl/monitor.c | 10 ++--
> 3 files changed, 67 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index b30f99335bbe..14126d228e61 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -414,7 +414,7 @@ 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, bool any_cpu,
> +bool resctrl_enable_mon_event(enum resctrl_event_id eventid, bool any_cpu,
> unsigned int binary_bits, void *arch_priv);
>
> bool resctrl_is_mon_event_enabled(enum resctrl_event_id eventid);
> diff --git a/arch/x86/kernel/cpu/resctrl/intel_aet.c b/arch/x86/kernel/cpu/resctrl/intel_aet.c
> index bb080bdde190..b6b50650e634 100644
> --- a/arch/x86/kernel/cpu/resctrl/intel_aet.c
> +++ b/arch/x86/kernel/cpu/resctrl/intel_aet.c
> @@ -20,9 +20,11 @@
> #include <linux/intel_pmt_features.h>
> #include <linux/intel_vsec.h>
> #include <linux/overflow.h>
> +#include <linux/printk.h>
> #include <linux/resctrl.h>
> #include <linux/resctrl_types.h>
> #include <linux/stddef.h>
> +#include <linux/topology.h>
> #include <linux/types.h>
>
> #include "internal.h"
> @@ -117,12 +119,68 @@ static struct event_group *known_event_groups[] = {
> _peg < &known_event_groups[ARRAY_SIZE(known_event_groups)]; \
> _peg++)
>
> -/* Stub for now */
> -static bool enable_events(struct event_group *e, struct pmt_feature_group *p)
> +/*
> + * Clear the address field of regions that did not pass the checks in
> + * skip_telem_region() so they will not be used by intel_aet_read_event().
> + * This is safe to do because intel_pmt_get_regions_by_feature() allocates
> + * a new pmt_feature_group structure to return to each caller and only makes
> + * use of the pmt_feature_group::kref field when intel_pmt_put_feature_group()
> + * returns the structure.
> + */
> +static void mark_telem_region_unusable(struct telemetry_region *tr)
> {
> + tr->addr = NULL;
> +}
> +
> +static bool skip_telem_region(struct telemetry_region *tr, struct event_group *e)
> +{
> + if (tr->guid != e->guid)
> + return true;
> + if (tr->plat_info.package_id >= topology_max_packages()) {
> + pr_warn("Bad package %u in guid 0x%x\n", tr->plat_info.package_id,
> + tr->guid);
> + return true;
> + }
> + if (tr->size != e->mmio_size) {
> + pr_warn("MMIO space wrong size (%zu bytes) for guid 0x%x. Expected %zu bytes.\n",
> + tr->size, e->guid, e->mmio_size);
> + return true;
> + }
> +
> return false;
> }
>
> +static bool group_has_usable_regions(struct event_group *e, struct pmt_feature_group *p)
> +{
> + bool usable_regions = false;
> +
> + for (int i = 0; i < p->count; i++) {
> + if (skip_telem_region(&p->regions[i], e)) {
> + mark_telem_region_unusable(&p->regions[i]);
> + continue;
> + }
> + usable_regions = true;
> + }
> +
> + return usable_regions;
> +}
> +
> +static bool enable_events(struct event_group *e, struct pmt_feature_group *p)
> +{
> + int skipped_events = 0;
> +
> + if (!group_has_usable_regions(e, p))
> + return false;
> +
> + for (int j = 0; j < e->num_events; j++) {
> + if (!resctrl_enable_mon_event(e->evts[j].id, true,
> + e->evts[j].bin_bits, &e->evts[j]))
> + skipped_events++;
> + }

The snippet below from patch #25 seems to belong here:
if (e->num_events == skipped_events) {
pr_info("No events enabled in %s %s:0x%x\n", r->name, e->name, e->guid);
return false;
}

> +
> + return skipped_events < e->num_events;
> +}
> +
> /*
> * Make a request to the INTEL_PMT_TELEMETRY driver for a copy of the
> * pmt_feature_group for each known feature. If there is one, the returned
> diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
> index 4ef91fc09070..338a122dfcff 100644
> --- a/fs/resctrl/monitor.c
> +++ b/fs/resctrl/monitor.c
> @@ -990,25 +990,27 @@ struct mon_evt mon_event_all[QOS_NUM_EVENTS] = {
> MON_EVENT(PMT_EVENT_UOPS_RETIRED, "uops_retired", RDT_RESOURCE_PERF_PKG, false),
> };
>
> -void resctrl_enable_mon_event(enum resctrl_event_id eventid, bool any_cpu,
> +bool resctrl_enable_mon_event(enum resctrl_event_id eventid, bool any_cpu,
> unsigned int binary_bits, void *arch_priv)
> {
> if (WARN_ON_ONCE(eventid < QOS_FIRST_EVENT || eventid >= QOS_NUM_EVENTS ||
> binary_bits > MAX_BINARY_BITS))
> - return;
> + return false;
> if (mon_event_all[eventid].enabled) {
> pr_warn("Duplicate enable for event %d\n", eventid);
> - return;
> + return false;
> }
> if (binary_bits && !mon_event_all[eventid].is_floating_point) {
> pr_warn("Event %d may not be floating point\n", eventid);
> - return;
> + return false;
> }
>
> mon_event_all[eventid].any_cpu = any_cpu;
> mon_event_all[eventid].binary_bits = binary_bits;
> mon_event_all[eventid].arch_priv = arch_priv;
> mon_event_all[eventid].enabled = true;
> +
> + return true;
> }
>
> bool resctrl_is_mon_event_enabled(enum resctrl_event_id eventid)

Reinette