On Fri, 13 Mar 2026 14:45:38 +0000
Ben Horgan [off-list ref] wrote:

From: Zeng Heng <redacted>

The per-RIS flag, in_reset_state, indicates whether or not the MSC
registers are in reset state, and allows avoiding resetting when they are
already in reset state. However, when mpam_apply_config() updates the
configuration it doesn't update the in_reset_state flag and so even after
the configuration update in_reset_state can be true and mpam_reset_ris()
will skip the actual register restoration on subsequent resets.

Once resctrl has a MPAM backend it will use resctrl_arch_reset_all_ctrls()
to reset the MSC configuration on unmount and, if the in_reset_state flag
is bogusly true, fail to reset the MSC configuration. The resulting
non-reset MSC configuration can lead to persistent performance restrictions
even after resctrl is unmounted.

Fix by clearing in_reset_state to false immediately after successful
configuration application, ensuring that the next reset operation
properly restores MSC register defaults.

Fixes: 09b89d2a72f3 ("arm_mpam: Allow configuration to be applied and restored during cpu online")
Signed-off-by: Zeng Heng <redacted>
Acked-by: Ben Horgan <ben.horgan@arm.com>
[Horgan: rewrite commit message to not be specific to resctrl unmount]
Signed-off-by: Ben Horgan <ben.horgan@arm.com>

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>