arm_mpam: Ensure in_reset_state is false after applying configuration

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@huawei.com>
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: Gavin Shan <gshan@redhat.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: James Morse <james.morse@arm.com>
Tested-by: Gavin Shan <gshan@redhat.com>
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Tested-by: Jesse Chick <jessechick@os.amperecomputing.com>
Signed-off-by: James Morse <james.morse@arm.com>

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 1eebc26021871d3dc573da488fe7bf9613a0b863..0fd6590a9b5c0bc211ece2915d2bb5706df69960 100644 (file)
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -2692,6 +2692,7 @@ int mpam_apply_config(struct mpam_component *comp, u16 partid,
                                         srcu_read_lock_held(&mpam_srcu)) {
                        arg.ris = ris;
                        mpam_touch_msc(msc, __write_config, &arg);
+                       ris->in_reset_state = false;
                }
                mutex_unlock(&msc->cfg_lock);
        }