Re: [ndctl PATCH v2 1/1] ndctl/cxl: Show region locked status to user

[Alison Schofield <alison.schofield@intel.com>]

On Wed, Apr 01, 2026 at 08:42:05PM +0800, Li Ming wrote:
> 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

Sorry Ming, I missed previously-

This always emits "locked":false on kernels without the new sysfs
attribute. Please make it skip the emit in that case.


> 
> Signed-off-by: Li Ming <ming.li@zohomail.com>
> ---
> v2:
> * Move lock status checking to the beginning of destroy_region().
>   (Alison)
> ---
>  cxl/json.c         |  4 ++++
>  cxl/lib/libcxl.c   | 11 +++++++++++
>  cxl/lib/libcxl.sym |  5 +++++
>  cxl/lib/private.h  |  1 +
>  cxl/libcxl.h       |  1 +
>  cxl/region.c       |  6 ++++++
>  6 files changed, 28 insertions(+)
> 
> diff --git a/cxl/json.c b/cxl/json.c
> index a0dc343..3bbe07a 100644
> --- a/cxl/json.c
> +++ b/cxl/json.c
> @@ -1077,6 +1077,10 @@ struct json_object *util_cxl_region_to_json(struct cxl_region *region,
>  			json_object_object_add(jregion, "state", jobj);
>  	}
>  
> +	jobj = json_object_new_boolean(cxl_region_is_locked(region));
> +	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)
> diff --git a/cxl/lib/libcxl.c b/cxl/lib/libcxl.c
> index 5e8deb6..ce2b364 100644
> --- a/cxl/lib/libcxl.c
> +++ b/cxl/lib/libcxl.c
> @@ -472,6 +472,11 @@ CXL_EXPORT int cxl_region_is_enabled(struct cxl_region *region)
>  	return is_enabled(path);
>  }
>  
> +CXL_EXPORT bool cxl_region_is_locked(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 +694,12 @@ 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 = false;
> +	else
> +		region->locked = strtoul(buf, NULL, 0);
> +
>  	cxl_region_foreach_safe(decoder, region_dup, _r)
>  		if (region_dup->id == region->id) {
>  			list_del_from(&decoder->regions, &region_dup->list);
> diff --git a/cxl/lib/libcxl.sym b/cxl/lib/libcxl.sym
> index 797e398..7c586f4 100644
> --- a/cxl/lib/libcxl.sym
> +++ b/cxl/lib/libcxl.sym
> @@ -315,3 +315,8 @@ global:
>  	cxl_memdev_clear_poison;
>  	cxl_debugfs_exists;
>  } LIBCXL_10;
> +
> +LIBCXL_12 {
> +global:
> +	cxl_region_is_locked;
> +} LIBCXL_11;
> diff --git a/cxl/lib/private.h b/cxl/lib/private.h
> index 582eebf..d074122 100644
> --- a/cxl/lib/private.h
> +++ b/cxl/lib/private.h
> @@ -189,6 +189,7 @@ struct cxl_region {
>  	u64 start;
>  	u64 size;
>  	u64 cache_size;
> +	bool locked;
>  	unsigned int interleave_ways;
>  	unsigned int interleave_granularity;
>  	enum cxl_decode_state decode_state;
> diff --git a/cxl/libcxl.h b/cxl/libcxl.h
> index a853ab6..6ff58de 100644
> --- a/cxl/libcxl.h
> +++ b/cxl/libcxl.h
> @@ -353,6 +353,7 @@ int cxl_region_clear_all_targets(struct cxl_region *region);
>  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);
> +bool cxl_region_is_locked(struct cxl_region *region);
>  
>  #define cxl_region_foreach(decoder, region)                                    \
>  	for (region = cxl_region_get_first(decoder); region != NULL;           \
> diff --git a/cxl/region.c b/cxl/region.c
> index 207cf2d..8a85522 100644
> --- a/cxl/region.c
> +++ b/cxl/region.c
> @@ -837,6 +837,12 @@ static int destroy_region(struct cxl_region *region)
>  	unsigned int ways, i;
>  	int rc;
>  
> +	if (cxl_region_is_locked(region)) {
> +		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) {
> -- 
> 2.43.0
>