Re: [PATCH v15 10/34] fs/resctrl: Introduce the interface to display monitoring modes

[Reinette Chatre]

Hi Babu,

On 7/8/25 3:17 PM, Babu Moger wrote:
> Introduce the resctrl file "mbm_assign_mode" to list the supported counter
> assignment modes.
> 
> The "mbm_event" counter assignment mode allows users to assign a hardware
> counter to an RMID, event pair and monitor bandwidth usage as long as it is
> assigned. The hardware continues to track the assigned counter until it is
> explicitly unassigned by the user. Each event within a resctrl group can be
> assigned independently in this mode.
> 
> On AMD systems "mbm_event" mode is backed by the ABMC (Assignable
> Bandwidth Monitoring Counters) hardware feature and is enabled by default.
> 
> The "default" mode is the existing mode that works without the explicit
> counter assignment, instead relying on dynamic counter assignment by
> hardware that may result in hardware not dedicating a counter resulting
> in monitoring data reads returning "Unavailable".
> 
> Provide an interface to display the monitor modes on the system.
> 
> $ cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
> [mbm_event]
> default
> 
> Add IS_ENABLED(CONFIG_RESCTRL_ASSIGN_FIXED) check to support Arm64.
> 
> On x86, CONFIG_RESCTRL_ASSIGN_FIXED is not defined. On Arm64, it will be
> defined when the "mbm_event" mode is supported.
> 
> Add IS_ENABLED(CONFIG_RESCTRL_ASSIGN_FIXED) check early to ensure the user
> interface remains compatible with upcoming Arm64 support. IS_ENABLED()
> safely evaluates to 0 when the configuration is not defined.
> 
> As a result, for MPAM, the display would be either:
> [default]
> or
> [mbm_event]
> 
> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> ---

Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>

Reinette