In mbm_cntr_assign mode, the hardware counter should be assigned to read
the MBM events.
Report 'Unassigned' in case the user attempts to read the events without
assigning the counter.
Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
v10: Moved the code to check the assign state inside mon_event_read().
Fixed few text comments.
v9: Used is_mbm_event() to check the event type.
Minor user documentation update.
v8: Used MBM_EVENT_ARRAY_INDEX to get the index for the MBM event.
Documentation update to make the text generic.
v7: Moved the documentation under "mon_data".
Updated the text little bit.
v6: Added more explaination in the resctrl.rst
Added checks to detect "Unassigned" before reading RMID.
v5: New patch.
---
Documentation/arch/x86/resctrl.rst | 10 ++++++++++
arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 8 ++++++++
arch/x86/kernel/cpu/resctrl/internal.h | 2 ++
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 4 ++--
4 files changed, 22 insertions(+), 2 deletions(-)
diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index c075fcee96b7..3ec14c314606 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -430,6 +430,16 @@ When monitoring is enabled all MON groups will also contain:
for the L3 cache they occupy). These are named "mon_sub_L3_YY"
where "YY" is the node number.
+ When supported the mbm_cntr_assign mode allows users to assign a
+ counter to mon_hw_id, event pair enabling bandwidth monitoring for
+ as long as the counter remains assigned. The hardware will continue
+ tracking the assigned mon_hw_id until the user manually unassigns
+ it, ensuring that counters are not reset during this period. With
+ a limited number of counters, the system may run out of assignable
+ counters. In that case, MBM event counters will return 'Unassigned'
+ when the event is read. Users must manually assign a counter to read
+ the events.
+
"mon_hw_id":
Available only with debug option. The identifier used by hardware
for the monitor group. On x86 this is the RMID.
diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index 200d89a64027..8e265a86e524 100644
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -527,6 +527,12 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
/* When picking a CPU from cpu_mask, ensure it can't race with cpuhp */
lockdep_assert_cpus_held();
+ if (resctrl_arch_mbm_cntr_assign_enabled(r) && is_mbm_event(evtid) &&
+ !mbm_cntr_assigned(r, d, rdtgrp, evtid)) {
+ rr->err = -ENOENT;
+ return;
+ }
+
/*
* Setup the parameters to pass to mon_event_count() to read the data.
*/
@@ -618,6 +624,8 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
seq_puts(m, "Error\n");
else if (rr.err == -EINVAL)
seq_puts(m, "Unavailable\n");
+ else if (rr.err == -ENOENT)
+ seq_puts(m, "Unassigned\n");
else
seq_printf(m, "%llu\n", rr.val);
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index f858098dbe4b..bb3213a7993e 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -710,4 +710,6 @@ int rdtgroup_unassign_cntr_event(struct rdt_resource *r, struct rdtgroup *rdtgrp
struct rdt_mon_domain *d, enum resctrl_event_id evtid);
struct mbm_state *get_mbm_state(struct rdt_mon_domain *d, u32 closid,
u32 rmid, enum resctrl_event_id evtid);
+bool mbm_cntr_assigned(struct rdt_resource *r, struct rdt_mon_domain *d,
+ struct rdtgroup *rdtgrp, enum resctrl_event_id evtid);
#endif /* _ASM_X86_RESCTRL_INTERNAL_H */
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 5acae525881a..8d00b1689a80 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1967,8 +1967,8 @@ static int resctrl_config_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
return ret;
}
-static bool mbm_cntr_assigned(struct rdt_resource *r, struct rdt_mon_domain *d,
- struct rdtgroup *rdtgrp, enum resctrl_event_id evtid)
+bool mbm_cntr_assigned(struct rdt_resource *r, struct rdt_mon_domain *d,
+ struct rdtgroup *rdtgrp, enum resctrl_event_id evtid)
{
int cntr_id;
--
2.34.1
