Re: [PATCH v6 01/40] arm_mpam: Ensure in_reset_state is false after applying configuration

[Jonathan Cameron]

On Fri, 13 Mar 2026 14:45:38 +0000
Ben Horgan <ben.horgan@xxxxxxx> wrote:

> From: Zeng Heng <zengheng4@xxxxxxxxxx>
> 
> 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 <zengheng4@xxxxxxxxxx>
> Acked-by: Ben Horgan <ben.horgan@xxxxxxx>
> [Horgan: rewrite commit message to not be specific to resctrl unmount]
> Signed-off-by: Ben Horgan <ben.horgan@xxxxxxx>
Reviewed-by: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>