[PATCH v6 6/7] fs/resctrl: Document that automatic counter assignment is best effort

[Ben Horgan <ben.horgan@arm.com>]

When using automatic counter assignment it's useful for a user to know
which counters they can expect to be assigned on group creation.

Document that automatic counter assignment is best effort and how to
discover any assignment failures.

Suggested-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
---
Changes since v4:
Point user to mbm_L3_assignments rather than last_cmd_status (Reinette)
Add "in all domains" (Reinette)

Changes since v5:
Add Reinette's R-b
---
 Documentation/filesystems/resctrl.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index 2898a51e6f4b..b388e9193896 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -479,6 +479,12 @@ with the following files:
 	"1":
 		Auto assignment is enabled.
 
+	Automatic counter assignment is done with best effort. If auto
+	assignment is enabled but there are not enough available counters then
+	monitor group creation could succeed while one or more events belonging
+	to the group may not have a counter assigned in all domains. Consult
+	mbm_L3_assignments for counter assignment states of the new groups.
+
 	Example::
 
 	  # echo 0 > /sys/fs/resctrl/info/L3_MON/mbm_assign_on_mkdir
-- 
2.43.0