Re: [PATCH v3 6/6] x86/resctrl: Add support for L3 occupancy monitoring via RMID MMIO read

[Thomas Gleixner]

On Sat, Jun 06 2026 at 10:38, Chen Yu wrote:

> The CMRC (Cache Monitoring Registers for CPU Agents Description)
> ACPI sub-table provides the MMIO address used to read the LLC
> occupancy counter for each RMID. When ERDT is enabled on the
> platform, use this MMIO interface instead of the legacy MSR read
> to obtain the L3 occupancy value.
>
> Introduce erdt_mon_read(), a helper that retrieves monitoring
> data for a given RMID and event ID from an ERDT domain. Initial
> support is added for the L3 occupancy monitoring event
> (QOS_L3_OCCUP_EVENT_ID).
>
> If the platform supports ERDT, CMRC-based MMIO access is used by
> default. If ERDT is unavailable, the implementation is to use
> MSR-based operations.
>
> Suggested-by: Tony Luck <tony.luck@xxxxxxxxx>
> Co-developed-by: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>
> Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>
> Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>

Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxx>