When the "mbm_event" counter assignment mode is enabled, a hardware counter
must be assigned to read the event.
Report 'Unassigned' in case the user attempts to read the event without
assigning a hardware counter.
Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
v15: Updated the changelog.
Removed the error setting in rdtgroup_mondata_show(). It is already done
in mon_event_read() based on the discussion.
https://lore.kernel.org/lkml/b4b14670-9cb0-4f65-abd5-39db996e8da9@xxxxxxxxx/
v14: Updated the changelog.
Added the code comment for "-ENOENT" when counter is read without assignement.
Removed the references to resctrl_is_mbm_event().
v13: Minor commitlog and user doc update.
Resolved conflicts caused by the recent FS/ARCH code restructure.
The monitor.c/rdtgroup.c files have been split between the FS and ARCH directories.
v12: Updated the documentation for more clarity.
v11: Domain can be NULL with SNC support so moved the unassign check in
rdtgroup_mondata_show().
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/filesystems/resctrl.rst | 8 ++++++++
fs/resctrl/ctrlmondata.c | 6 ++++++
2 files changed, 14 insertions(+)
diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index 446736dbd97f..4f5eb5bbd4b5 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -434,6 +434,14 @@ 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.
+ The "mbm_event" counter assignment mode offers "num_mbm_cntrs" number of
+ counters and allows users to assign counters to mon_hw_id, event pairs
+ enabling bandwidth monitoring for as long as the counter remains assigned.
+ The hardware will continue tracking the assigned counter until the user
+ manually unassigns it, ensuring that event data is not reset during this
+ period. An MBM event returns 'Unassigned' when the event does not have
+ a hardware counter assigned.
+
"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/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
index ce766b2cdfc1..45351673e4ee 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -661,10 +661,16 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
checkresult:
+ /*
+ * -ENOENT is a special case, set only when "mbm_event" counter assignment
+ * mode is enabled and no counter has been assigned.
+ */
if (rr.err == -EIO)
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);
--
2.34.1
