Re: [PATCH v2 11/29] arm_mpam: Probe hardware to find the supported partid/pmg values

Ben Horgan
2025-09-12T11:11:10Z

Hi James,

On 9/10/25 21:42, James Morse wrote:
> CPUs can generate traffic with a range of PARTID and PMG values,
> but each MSC may also have its own maximum size for these fields.
> Before MPAM can be used, the driver needs to probe each RIS on
> each MSC, to find the system-wide smallest value that can be used.
> The limits from requestors (e.g. CPUs) also need taking into account.
>
> While doing this, RIS entries that firmware didn't describe are created
> under MPAM_CLASS_UNKNOWN.
>
> While we're here, implement the mpam_register_requestor() call
> for the arch code to register the CPU limits. Future callers of this
> will tell us about the SMMU and ITS.
>
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
> Changes since v1:
> * Change to lock ordering now that the list-lock mutex isn't held from
> the cpuhp call.
> * Removed irq-unmaksed assert in requestor register.
> * Changed captialisation in print message.
> ---
> drivers/resctrl/mpam_devices.c | 150 +++++++++++++++++++++++++++++++-
> drivers/resctrl/mpam_internal.h | 6 ++
> include/linux/arm_mpam.h | 14 +++
> 3 files changed, 169 insertions(+), 1 deletion(-)

Looks good to me. I think Jonathan's comment on getting rid of the local
variable, 'found', is worthwhile.

Reviewed-by: Ben Horgan <ben.horgan@arm.com>

Thanks,

Ben