[PATCH v12 10/26] x86/resctrl: Introduce mbm_cntr_cfg to track assignable counters at domain

Babu Moger
2025-04-04T00:20:23Z

In mbm_cntr_assign mode hardware counters are assigned/unassigned to an
MBM event of a monitor group. Hardware counters are assigned/unassigned
at monitoring domain level.

Manage a monitoring domain's hardware counters using a per monitoring
domain array of struct mbm_cntr_cfg that is indexed by the hardware
counter ID. A hardware counter's configuration contains the MBM event
ID and points to the monitoring group that it is assigned to, with a
NULL pointer meaning that the hardware counter is available for assignment.

There is no direct way to determine which hardware counters are assigned
to a particular monitoring group. Check every entry of every hardware
counter configuration array in every monitoring domain to query which
MBM events of a monitoring group is tracked by hardware. Such queries are
acceptable because of a very small number of assignable counters (32
to 64).

Suggested-by: Peter Newman <peternewman@google.com>
Signed-off-by: Babu Moger <babu.moger@amd.com>
---
v12: Fixed the struct mbm_cntr_cfg code documentation.
Removed few strange charactors in changelog.
Added the counter range for better understanding.
Moved the struct mbm_cntr_cfg definition to resctrl/internal.h as
suggested by James.

v11: Refined the change log based on Reinette's feedback.
Fixed few style issues.

v10: Patch changed completely to handle the counters at domain level.
https://lore.kernel.org/lkml/CALPaoCj+zWq1vkHVbXYP0znJbe6Ke3PXPWjtri5AFgD9cQDCUg@mail.gmail.com/
Removed Reviewed-by tag.
Did not see the need to add cntr_id in mbm_state structure. Not used in the code.

v9: Added Reviewed-by tag. No other changes.

v8: Minor commit message changes.

v7: Added check mbm_cntr_assignable for allocating bitmap mbm_cntr_map

v6: New patch to add domain level assignment.
---
arch/x86/kernel/cpu/resctrl/internal.h | 14 ++++++++++++++
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 11 +++++++++++
include/linux/resctrl.h | 2 ++
3 files changed, 27 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index ad4789740a33..e4b169fd6970 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -244,6 +244,20 @@ struct rdtgroup {
struct pseudo_lock_region *plr;
};

+/**
+ * struct mbm_cntr_cfg - assignable counter configuration
+ * @evtid: MBM event to which the counter is assigned. Only valid
+ * if @rdtgroup is not NULL.
+ * @evt_cfg: Event configuration value.
+ * @rdtgrp: resctrl group assigned to the counter. NULL if the
+ * counter is free.
+ */
+struct mbm_cntr_cfg {
+ enum resctrl_event_id evtid;
+ u32 evt_cfg;
+ struct rdtgroup *rdtgrp;
+};
+
/* rdtgroup.flags */
#define RDT_DELETED 1

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 0c9d7a702b93..cb7a8a2de3ff 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -4127,6 +4127,7 @@ static void __init rdtgroup_setup_default(void)

static void domain_destroy_mon_state(struct rdt_mon_domain *d)
{
+ kfree(d->cntr_cfg);
bitmap_free(d->rmid_busy_llc);
kfree(d->mbm_total);
kfree(d->mbm_local);
@@ -4213,6 +4214,16 @@ static int domain_setup_mon_state(struct rdt_resource *r, struct rdt_mon_domain
return -ENOMEM;
}
}
+ if (resctrl_is_mbm_enabled() && r->mon.mbm_cntr_assignable) {
+ tsize = sizeof(*d->cntr_cfg);
+ d->cntr_cfg = kcalloc(r->mon.num_mbm_cntrs, tsize, GFP_KERNEL);
+ if (!d->cntr_cfg) {
+ bitmap_free(d->rmid_busy_llc);
+ kfree(d->mbm_total);
+ kfree(d->mbm_local);
+ return -ENOMEM;
+ }
+ }

return 0;
}
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 8247c33bbf5a..294b15de664e 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -153,6 +153,7 @@ struct rdt_ctrl_domain {
* @cqm_limbo: worker to periodically read CQM h/w counters
* @mbm_work_cpu: worker CPU for MBM h/w counters
* @cqm_work_cpu: worker CPU for CQM h/w counters
+ * @cntr_cfg: assignable counters configuration
*/
struct rdt_mon_domain {
struct rdt_domain_hdr hdr;
@@ -164,6 +165,7 @@ struct rdt_mon_domain {
struct delayed_work cqm_limbo;
int mbm_work_cpu;
int cqm_work_cpu;
+ struct mbm_cntr_cfg *cntr_cfg;
};

/**
--
2.34.1