[PATCH] arm_mpam: Restore the cached configuration when a write to an MSC fails

[Jinjie Ruan]

mpam_apply_config() caches the new configuration before writing it to
the RISes. When mpam_touch_msc() fails, the cache keeps the new values,
so a retry with the same schemata is skipped as a no-op and never
reaches the hardware.

Restore the cached configuration on failure so the retry writes it to
the RISes again.

Only arm64 MPAM systems are affected; x86 does not support MPAM.

Fixes: 60e33a1864fd ("arm_mpam: propagate MSC access errors for mpam_reprogram_ris_partid()")
Signed-off-by: Jinjie Ruan <ruanjinjie at huawei.com>
Cc: <stable at vger.kernel.org> # 7.4.x
---
 drivers/resctrl/mpam_devices.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index c067b6d57d71..bb667a416660 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -3412,6 +3412,7 @@ static bool mpam_update_config(struct mpam_config *cfg,
 int mpam_apply_config(struct mpam_component *comp, u16 partid,
 		      struct mpam_config *cfg)
 {
+	struct mpam_config old_cfg = comp->cfg[partid];
 	struct mpam_write_config_arg arg;
 	struct mpam_msc_ris *ris;
 	struct mpam_vmsc *vmsc;
@@ -3439,8 +3440,10 @@ int mpam_apply_config(struct mpam_component *comp, u16 partid,
 					 srcu_read_lock_held(&mpam_srcu)) {
 			arg.ris = ris;
 			ret = mpam_touch_msc(msc, __write_config, &arg);
-			if (ret)
+			if (ret) {
+				comp->cfg[partid] = old_cfg;
 				return ret;
+			}
 			ris->in_reset_state = false;
 		}
 	}
-- 
2.34.1