arm64/mpam: add cmdline option: mpam

hulk inclusion
category: feature
bugzilla: 10897
CVE: NA

MPAM feature is just for debug and preview in this version,
so disable it by default. You can enable it by cmdline: "mpam".
Signed-off-by: NXie XiuQi <xiexiuqi@huawei.com>
Reviewed-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

arch/arm64/include/asm/mpam_sched.h

@@ -39,6 +39,8 @@ static inline void mpam_sched_in(void)
 		__mpam_sched_in();
 }
 
+extern int __read_mostly mpam_enabled;
+
 #else
 
 static inline void mpam_sched_in(void) {}

arch/arm64/kernel/mpam.c

@@ -1242,11 +1242,23 @@ static void mpam_domains_init(struct resctrl_resource *r)
 	}
 }
 
+int __read_mostly mpam_enabled;
+
+static int __init mpam_setup(char *str)
+{
+	mpam_enabled = 1;
+	return 1;
+}
+__setup("mpam", mpam_setup);
+
 static int __init mpam_late_init(void)
 {
 	struct resctrl_resource *r;
 	int state, ret;
 
+	if (!mpam_enabled)
+		return 0;
+
 	if (!cpus_have_const_cap(ARM64_HAS_MPAM))
 		return -ENODEV;