cxl/list: show region locked status to user

A region is not allowed to be destroyed if it is in locked status.
cxl destroy-region command will fail and ask user to try it again as
root, but it is not the real reason and it will confuse user if user is
already a root user. This patch will show the region locked status in
region information and output an explicit log to user that operation is
not permitted like below.

Before the patch:
cxl list -ir region0
[
  {
    "region":"region0",
    "resource":53955526656,
    "size":536870912,
    "type":"ram",
    "interleave_ways":2,
    "interleave_granularity":256,
    "decode_state":"commit",
    "state":"disabled",
    "qos_class_mismatch":true
  }
]
cxl destroy-region region0
libcxl: write_attr: failed to write 0
 to /sys/bus/cxl/devices/root0/decoder0.0/region0/commit: Operation not permitted hint: try running as root or using sudo
cxl region: destroy_region: region0: failed to reset decode: Operation not permitted
cxl region: decoder_region_action: region0: failed: Operation not permitted
cxl region: region_action: one or more failures, last failure: Operation not permitted
cxl region: cmd_destroy_region: destroyed 0 regions

After the patch:
cxl list -ir region0
[
  {
    "region":"region0",
    "resource":53955526656,
    "size":536870912,
    "type":"ram",
    "interleave_ways":2,
    "interleave_granularity":256,
    "decode_state":"commit",
    "state":"disabled",
    "locked":true,
    "qos_class_mismatch":true
  }
]
cxl destroy-region region0
cxl region: destroy_region: region0: Cannot destroy a locked region.
cxl region: decoder_region_action: region0: failed: Operation not permitted
cxl region: region_action: one or more failures, last failure: Operation not permitted
cxl region: cmd_destroy_region: destroyed 0 regions

[ as: return enum cxl_region_locked_state from accessor,
      map sysfs values explicitly to enum states,
      replace enum-to-bool conversion with explicit enum comparisons ]

Signed-off-by: Li Ming <ming.li@zohomail.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Tested-by: Alison Schofield <alison.schofield@intel.com>
Link: https://lore.kernel.org/r/20260403050459.2236-1-ming.li@zohomail.com
Signed-off-by: Alison Schofield <alison.schofield@intel.com>

Author: liming011

cxl/json.c

@@ -1007,6 +1007,7 @@ struct json_object *util_cxl_region_to_json(struct cxl_region *region,
 {
 	enum cxl_decoder_mode mode = cxl_region_get_mode(region);
 	const char *devname = cxl_region_get_devname(region);
+	enum cxl_region_locked_state state;
 	struct json_object *jregion, *jobj;
 	u64 val;
 
@@ -1077,6 +1078,13 @@ struct json_object *util_cxl_region_to_json(struct cxl_region *region,
 			json_object_object_add(jregion, "state", jobj);
 	}
 
+	state = cxl_region_locked_state(region);
+	if (state != CXL_REGION_LOCKED_UNKNOWN) {
+		jobj = json_object_new_boolean(state == CXL_REGION_LOCKED);
+		if (jobj)
+			json_object_object_add(jregion, "locked", jobj);
+	}
+
 	if (flags & UTIL_JSON_MEDIA_ERRORS) {
 		jobj = util_cxl_poison_list_to_json(region, NULL, flags);
 		if (jobj)

cxl/lib/libcxl.c

@@ -472,6 +472,12 @@ CXL_EXPORT int cxl_region_is_enabled(struct cxl_region *region)
 	return is_enabled(path);
 }
 
+CXL_EXPORT enum cxl_region_locked_state
+cxl_region_locked_state(struct cxl_region *region)
+{
+	return region->locked;
+}
+
 CXL_EXPORT bool cxl_region_qos_class_mismatch(struct cxl_region *region)
 {
 	struct cxl_decoder *root_decoder = cxl_region_get_decoder(region);
@@ -689,6 +695,13 @@ static void *add_cxl_region(void *parent, int id, const char *cxlregion_base)
 	if (sysfs_read_attr(ctx, path, buf) == 0)
 		region->module = util_modalias_to_module(ctx, buf);
 
+	sprintf(path, "%s/locked", cxlregion_base);
+	if (sysfs_read_attr(ctx, path, buf) < 0)
+		region->locked = CXL_REGION_LOCKED_UNKNOWN;
+	else
+		region->locked = strtoul(buf, NULL, 0) ?
+			CXL_REGION_LOCKED : CXL_REGION_UNLOCKED;
+
 	cxl_region_foreach_safe(decoder, region_dup, _r)
 		if (region_dup->id == region->id) {
 			list_del_from(&decoder->regions, &region_dup->list);

cxl/lib/libcxl.sym

@@ -315,3 +315,8 @@ global:
 	cxl_memdev_clear_poison;
 	cxl_debugfs_exists;
 } LIBCXL_10;
+
+LIBCXL_12 {
+global:
+	cxl_region_locked_state;
+} LIBCXL_11;

cxl/lib/private.h

@@ -189,6 +189,7 @@ struct cxl_region {
 	u64 start;
 	u64 size;
 	u64 cache_size;
+	enum cxl_region_locked_state locked;
 	unsigned int interleave_ways;
 	unsigned int interleave_granularity;
 	enum cxl_decode_state decode_state;

cxl/libcxl.h

@@ -354,6 +354,15 @@ int cxl_region_decode_commit(struct cxl_region *region);
 int cxl_region_decode_reset(struct cxl_region *region);
 bool cxl_region_qos_class_mismatch(struct cxl_region *region);
 
+enum cxl_region_locked_state {
+	CXL_REGION_LOCKED_UNKNOWN = -1,
+	CXL_REGION_UNLOCKED,
+	CXL_REGION_LOCKED,
+};
+
+enum cxl_region_locked_state
+cxl_region_locked_state(struct cxl_region *region);
+
 #define cxl_region_foreach(decoder, region)                                    \
 	for (region = cxl_region_get_first(decoder); region != NULL;           \
 	     region = cxl_region_get_next(region))

cxl/region.c

@@ -837,6 +837,12 @@ static int destroy_region(struct cxl_region *region)
 	unsigned int ways, i;
 	int rc;
 
+	if (cxl_region_locked_state(region) == CXL_REGION_LOCKED) {
+		log_err(&rl, "%s: cannot destroy a locked region\n",
+			devname);
+		return -EPERM;
+	}
+
 	/* First, unbind/disable the region if needed */
 	if (cxl_region_is_enabled(region)) {
 		if (param.force) {