diff --git a/arch/arm64/kernel/mpam/mpam_resctrl.c b/arch/arm64/kernel/mpam/mpam_resctrl.c
index 79b711e2b7a5c452a88933d22e1c0ef3b1c27c44..80f402476abbfaca532e2db5fa2db34bf8214b4c 100644
--- a/arch/arm64/kernel/mpam/mpam_resctrl.c
+++ b/arch/arm64/kernel/mpam/mpam_resctrl.c
@@ -1890,12 +1890,14 @@ static ssize_t resctrl_group_rmid_write(struct kernfs_open_file *of,
 
 	if (rmid == 0 || rdtgrp->mon.rmid == 0) {
 		ret = -EINVAL;
+		rdt_last_cmd_puts("default rmid 0 is always kept\n");
 		goto unlock;
 	}
 
 	ret = rmid_to_partid_pmg(rmid, &partid, &pmg);
 	if (ret < 0) {
 		ret = -EINVAL;
+		rdt_last_cmd_puts("invalid rmid\n");
 		goto unlock;
 	}
 
@@ -1904,6 +1906,7 @@ static ssize_t resctrl_group_rmid_write(struct kernfs_open_file *of,
 
 	if (rdtgrp->type != RDTCTRL_GROUP ||
 			!list_empty(&rdtgrp->mon.crdtgrp_list)) {
+		ret = -EINVAL;
 		rdt_last_cmd_puts("unsupported operation\n");
 		goto unlock;
 	}