Re: [PATCH v4 05/41] arm64: mpam: Re-initialise MPAM regs when CPU comes online

Catalin Marinas
2026-02-05T16:20:42Z

On Tue, Feb 03, 2026 at 09:43:06PM +0000, Ben Horgan wrote:
> From: James Morse <james.morse@arm.com>
>
> Now that the MPAM system registers are expected to have values that change,
> reprogram them based on the previous value when a CPU is brought online.
>
> Previously MPAM's 'default PARTID' of 0 was always used for MPAM in
> kernel-space as this is the PARTID that hardware guarantees to
> reset. Because there are a limited number of PARTID, this value is exposed
> to user-space, meaning resctrl changes to the resctrl default group would
> also affect kernel threads. Instead, use the task's PARTID value for
> kernel work on behalf of user-space too. The default of 0 is kept for both
> user-space and kernel-space when MPAM is not enabled.
>
> Tested-by: Gavin Shan <gshan@redhat.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
> Tested-by: Peter Newman <peternewman@google.com>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>