arm64/mpam: Supplement err tips in info/last_cmd_status

hulk inclusion
category: bugfix
bugzilla: 48265
CVE: NA

--------------------------------

In many cases writing resctrl interface may return failure, but
err tips in info/last_cmd_status remain ok.
e.g.
    > echo 'L3:5=7fff' > schemata
      -bash: echo: write error: Invalid argument
    > cat info/last_cmd_status
      ok
    > cat ctrlmon
      1
    > echo 1 > ctrlmon
      -bash: echo: write error: No such file or directory
    > cat info/last_cmd_status
      ok
We add extra tips when goes to this branches.
Signed-off-by: NWang ShaoBo <bobo.shaobowang@huawei.com>
Reviewed-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NCheng Jian <cj.chengjian@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/arm64/kernel/mpam.c

@@ -858,7 +858,7 @@ static int resctrl_num_mon_show(struct kernfs_open_file *of,
 int cpus_mon_write(struct rdtgroup *rdtgrp, cpumask_var_t newmask,
 		   cpumask_var_t tmpmask)
 {
-	pr_info("unsupported on mon_groups, please use ctrlmon groups\n");
+	rdt_last_cmd_puts("temporarily unsupported write cpus on mon_groups\n");
 	return -EINVAL;
 }
 
@@ -1143,6 +1143,7 @@ static ssize_t resctrl_group_ctrlmon_write(struct kernfs_open_file *of,
 
 	if (!rdtgrp) {
 		ret = -ENOENT;
+		rdt_last_cmd_puts("directory was removed\n");
 		goto unlock;
 	}
 
@@ -1156,6 +1157,10 @@ static ssize_t resctrl_group_ctrlmon_write(struct kernfs_open_file *of,
 		if (!ret)
 			rdtgrp->flags |= RDT_CTRLMON;
 	} else {
+		if (ctrlmon)
+			rdt_last_cmd_printf("ctrlmon has been enabled\n");
+		else
+			rdt_last_cmd_printf("ctrlmon has been disabled\n");
 		ret = -ENOENT;
 	}
 

arch/arm64/kernel/mpam_ctrlmon.c

@@ -171,6 +171,9 @@ static int parse_line(char *line, struct resctrl_resource *r)
 			goto next;
 		}
 	}
+
+	rdt_last_cmd_printf("unknown domain (%lu)\n", dom_id);
+
 	return -EINVAL;
 }
 
@@ -224,6 +227,7 @@ ssize_t resctrl_group_schemata_write(struct kernfs_open_file *of,
 	rdtgrp = resctrl_group_kn_lock_live(of->kn);
 	if (!rdtgrp) {
 		resctrl_group_kn_unlock(of->kn);
+		rdt_last_cmd_puts("directory was removed\n");
 		return -ENOENT;
 	}
 	rdt_last_cmd_clear();