x86/resctrl: Document the new "mba_MBps_event" file

Add a section to document a new read/write file that shows/sets the memory
bandwidth event used to control bandwidth used by each CTRL_MON group.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Link: https://lore.kernel.org/r/20241206163148.83828-9-tony.luck@intel.com

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index a824affd741d1e61d991f459e71abcf7365f90ef..6768fc1fad166fec03953dd91657ee3d264eea53 100644 (file)
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -384,6 +384,16 @@ When monitoring is enabled all MON groups will also contain:
        Available only with debug option. The identifier used by hardware
        for the monitor group. On x86 this is the RMID.
 
+When the "mba_MBps" mount option is used all CTRL_MON groups will also contain:
+
+"mba_MBps_event":
+       Reading this file shows which memory bandwidth event is used
+       as input to the software feedback loop that keeps memory bandwidth
+       below the value specified in the schemata file. Writing the
+       name of one of the supported memory bandwidth events found in
+       /sys/fs/resctrl/info/L3_MON/mon_features changes the input
+       event.
+
 Resource allocation rules
 -------------------------