Re: [PATCH 18/33] arm_mpam: Reset MSC controls from cpuhp callbacks

Gavin Shan
2025-11-09T22:11:45Z

On 11/7/25 10:34 PM, Ben Horgan wrote:
> From: James Morse <james.morse@arm.com>
>
> When a CPU comes online, it may bring a newly accessible MSC with
> it. Only the default partid has its value reset by hardware, and
> even then the MSC might not have been reset since its config was
> previously dirtied. e.g. Kexec.
>
> Any in-use partid must have its configuration restored, or reset.
> In-use partids may be held in caches and evicted later.
>
> MSC are also reset when CPUs are taken offline to cover cases where
> firmware doesn't reset the MSC over reboot using UEFI, or kexec
> where there is no firmware involvement.
>
> If the configuration for a RIS has not been touched since it was
> brought online, it does not need resetting again.
>
> To reset, write the maximum values for all discovered controls.
>
> CC: Rohit Mathew <Rohit.Mathew@arm.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> Reviewed-by: Fenghua Yu <fenghuay@nvidia.com>
> Tested-by: Fenghua Yu <fenghuay@nvidia.com>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
> Tested-by: Peter Newman <peternewman@google.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> ---
> Changes since v3:
> Add tags - thanks!
> ---
> drivers/resctrl/mpam_devices.c | 109 ++++++++++++++++++++++++++++++++
> drivers/resctrl/mpam_internal.h | 3 +
> 2 files changed, 112 insertions(+)
>

Reviewed-by: Gavin Shan <gshan@redhat.com>