[PATCH v3 1/2] cxl: Add cxl_decoders_committed() helper

[PATCH v3 1/2] cxl: Add cxl_decoders_committed() helper

[Dave Jiang]

Add a helper to retrieve the number of decoders committed for the port.
Replace all the open coding of the calculation with the helper.

Link: https://lore.kernel.org/linux-cxl/651c98472dfed_ae7e729495@dwillia2-xfh.jf.intel.com.notmuch/
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

---
v3:
- Rename cxl_decoders_committed() to cxl_num_decoders_comitted() (Jim)
- Compare cxl_num_decoders_committed() to 0 to improve readability (Jim)
v2:
- Remove EXPORT_SYMBOL() (Dan)
- Rebase on top of Dan's Fix shutdown order series, to pick up
  cxl_region_rwsem export.
---
 drivers/cxl/core/hdm.c    |    7 ++++---
 drivers/cxl/core/mbox.c   |    2 +-
 drivers/cxl/core/memdev.c |    4 ++--
 drivers/cxl/core/port.c   |    7 +++++++
 drivers/cxl/cxl.h         |    1 +
 5 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
index 506c9e14cdf9..7d112557c939 100644
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -643,10 +643,11 @@ static int cxl_decoder_commit(struct cxl_decoder *cxld)
 	if (cxld->flags & CXL_DECODER_F_ENABLE)
 		return 0;
 
-	if (port->commit_end + 1 != id) {
+	if (cxl_num_decoders_committed(port) != id) {
 		dev_dbg(&port->dev,
 			"%s: out of order commit, expected decoder%d.%d\n",
-			dev_name(&cxld->dev), port->id, port->commit_end + 1);
+			dev_name(&cxld->dev), port->id,
+			cxl_num_decoders_committed(port));
 		return -EBUSY;
 	}
 
@@ -863,7 +864,7 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
 			cxld->target_type = CXL_DECODER_HOSTONLYMEM;
 		else
 			cxld->target_type = CXL_DECODER_DEVMEM;
-		if (cxld->id != port->commit_end + 1) {
+		if (cxld->id != cxl_num_decoders_committed(port)) {
 			dev_warn(&port->dev,
 				 "decoder%d.%d: Committed out of order\n",
 				 port->id, cxld->id);
diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
index 67aec57cc12f..04033b06f75f 100644
--- a/drivers/cxl/core/mbox.c
+++ b/drivers/cxl/core/mbox.c
@@ -1200,7 +1200,7 @@ int cxl_mem_sanitize(struct cxl_memdev *cxlmd, u16 cmd)
 	 * Require an endpoint to be safe otherwise the driver can not
 	 * be sure that the device is unmapped.
 	 */
-	if (endpoint && endpoint->commit_end == -1)
+	if (endpoint && cxl_num_decoders_committed(endpoint) == 0)
 		rc = __cxl_mem_sanitize(mds, cmd);
 	else
 		rc = -EBUSY;
diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
index fed9573cf355..fc5c2b414793 100644
--- a/drivers/cxl/core/memdev.c
+++ b/drivers/cxl/core/memdev.c
@@ -231,7 +231,7 @@ int cxl_trigger_poison_list(struct cxl_memdev *cxlmd)
 	if (rc)
 		return rc;
 
-	if (port->commit_end == -1) {
+	if (cxl_num_decoders_committed(port) == 0) {
 		/* No regions mapped to this memdev */
 		rc = cxl_get_poison_by_memdev(cxlmd);
 	} else {
@@ -282,7 +282,7 @@ static struct cxl_region *cxl_dpa_to_region(struct cxl_memdev *cxlmd, u64 dpa)
 		.dpa = dpa,
 	};
 	port = cxlmd->endpoint;
-	if (port && is_cxl_endpoint(port) && port->commit_end != -1)
+	if (port && is_cxl_endpoint(port) && cxl_num_decoders_committed(port))
 		device_for_each_child(&port->dev, &ctx, __cxl_dpa_to_region);
 
 	return ctx.cxlr;
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 5ba606c6e03f..d0ed98a6bade 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -37,6 +37,13 @@ DECLARE_RWSEM(cxl_region_rwsem);
 static DEFINE_IDA(cxl_port_ida);
 static DEFINE_XARRAY(cxl_root_buses);
 
+int cxl_num_decoders_committed(struct cxl_port *port)
+{
+	lockdep_assert_held(&cxl_region_rwsem);
+
+	return port->commit_end + 1;
+}
+
 static ssize_t devtype_show(struct device *dev, struct device_attribute *attr,
 			    char *buf)
 {
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 76d92561af29..36bd3f06dd90 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -679,6 +679,7 @@ static inline bool is_cxl_root(struct cxl_port *port)
 	return port->uport_dev == port->dev.parent;
 }
 
+int cxl_num_decoders_committed(struct cxl_port *port);
 bool is_cxl_port(const struct device *dev);
 struct cxl_port *to_cxl_port(const struct device *dev);
 struct pci_bus;

[PATCH v3 2/2] cxl: Add decoders_committed sysfs attribute to cxl_port

[Dave Jiang]

This attribute allows cxl-cli to determine whether there are decoders
committed to a memdev.  This is only a snapshot of the state, and
doesn't offer any protection or serialization against a concurrent
disable-region operation.

Reviewed-by: Jim Harris <jim.harris@samsung.com>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
---
v2:
- Use cxl_region_rwsem to protect reading of decoder info. (Dan)
---
 drivers/cxl/core/port.c |   25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index d0ed98a6bade..0adee1e406ec 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -534,8 +534,33 @@ static void cxl_port_release(struct device *dev)
 	kfree(port);
 }
 
+static ssize_t decoders_committed_show(struct device *dev,
+				       struct device_attribute *attr, char *buf)
+{
+	struct cxl_port *port = to_cxl_port(dev);
+	int rc;
+
+	down_read(&cxl_region_rwsem);
+	rc = sysfs_emit(buf, "%d\n", cxl_num_decoders_committed(port));
+	up_read(&cxl_region_rwsem);
+
+	return rc;
+}
+
+static DEVICE_ATTR_RO(decoders_committed);
+
+static struct attribute *cxl_port_attrs[] = {
+	&dev_attr_decoders_committed.attr,
+	NULL,
+};
+
+static struct attribute_group cxl_port_attribute_group = {
+	.attrs = cxl_port_attrs,
+};
+
 static const struct attribute_group *cxl_port_attribute_groups[] = {
 	&cxl_base_attribute_group,
+	&cxl_port_attribute_group,
 	NULL,
 };
 

Re: [PATCH v3 1/2] cxl: Add cxl_decoders_committed() helper

[Jim Harris]

> On Oct 16, 2023, at 10:57 AM, Dave Jiang <dave.jiang@intel.com> wrote:
> 
> Add a helper to retrieve the number of decoders committed for the port.
> Replace all the open coding of the calculation with the helper.
> 
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>

Reviewed-by: Jim Harris <jim.harris@samsung.com>

Re: [PATCH v3 1/2] cxl: Add cxl_decoders_committed() helper

[Jonathan Cameron]

On Mon, 16 Oct 2023 10:57:48 -0700
Dave Jiang <dave.jiang@intel.com> wrote:

> Add a helper to retrieve the number of decoders committed for the port.
> Replace all the open coding of the calculation with the helper.
> 
> Link: https://lore.kernel.org/linux-cxl/651c98472dfed_ae7e729495@dwillia2-xfh.jf.intel.com.notmuch/
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> 
> ---
> v3:
> - Rename cxl_decoders_committed() to cxl_num_decoders_comitted() (Jim)
> - Compare cxl_num_decoders_committed() to 0 to improve readability (Jim)
> v2:
> - Remove EXPORT_SYMBOL() (Dan)
> - Rebase on top of Dan's Fix shutdown order series, to pick up
>   cxl_region_rwsem export.
> ---
>  drivers/cxl/core/hdm.c    |    7 ++++---
>  drivers/cxl/core/mbox.c   |    2 +-
>  drivers/cxl/core/memdev.c |    4 ++--
>  drivers/cxl/core/port.c   |    7 +++++++
>  drivers/cxl/cxl.h         |    1 +
>  5 files changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 506c9e14cdf9..7d112557c939 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -643,10 +643,11 @@ static int cxl_decoder_commit(struct cxl_decoder *cxld)
>  	if (cxld->flags & CXL_DECODER_F_ENABLE)
>  		return 0;
>  
> -	if (port->commit_end + 1 != id) {
> +	if (cxl_num_decoders_committed(port) != id) {
>  		dev_dbg(&port->dev,
>  			"%s: out of order commit, expected decoder%d.%d\n",
> -			dev_name(&cxld->dev), port->id, port->commit_end + 1);
> +			dev_name(&cxld->dev), port->id,
> +			cxl_num_decoders_committed(port));
>  		return -EBUSY;
>  	}
>  
> @@ -863,7 +864,7 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
>  			cxld->target_type = CXL_DECODER_HOSTONLYMEM;
>  		else
>  			cxld->target_type = CXL_DECODER_DEVMEM;
> -		if (cxld->id != port->commit_end + 1) {
> +		if (cxld->id != cxl_num_decoders_committed(port)) {
>  			dev_warn(&port->dev,
>  				 "decoder%d.%d: Committed out of order\n",
>  				 port->id, cxld->id);
> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> index 67aec57cc12f..04033b06f75f 100644
> --- a/drivers/cxl/core/mbox.c
> +++ b/drivers/cxl/core/mbox.c
> @@ -1200,7 +1200,7 @@ int cxl_mem_sanitize(struct cxl_memdev *cxlmd, u16 cmd)
>  	 * Require an endpoint to be safe otherwise the driver can not
>  	 * be sure that the device is unmapped.
>  	 */
> -	if (endpoint && endpoint->commit_end == -1)
> +	if (endpoint && cxl_num_decoders_committed(endpoint) == 0)
>  		rc = __cxl_mem_sanitize(mds, cmd);
>  	else
>  		rc = -EBUSY;
> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> index fed9573cf355..fc5c2b414793 100644
> --- a/drivers/cxl/core/memdev.c
> +++ b/drivers/cxl/core/memdev.c
> @@ -231,7 +231,7 @@ int cxl_trigger_poison_list(struct cxl_memdev *cxlmd)
>  	if (rc)
>  		return rc;
>  
> -	if (port->commit_end == -1) {
> +	if (cxl_num_decoders_committed(port) == 0) {
>  		/* No regions mapped to this memdev */
>  		rc = cxl_get_poison_by_memdev(cxlmd);
>  	} else {
> @@ -282,7 +282,7 @@ static struct cxl_region *cxl_dpa_to_region(struct cxl_memdev *cxlmd, u64 dpa)
>  		.dpa = dpa,
>  	};
>  	port = cxlmd->endpoint;
> -	if (port && is_cxl_endpoint(port) && port->commit_end != -1)
> +	if (port && is_cxl_endpoint(port) && cxl_num_decoders_committed(port))
>  		device_for_each_child(&port->dev, &ctx, __cxl_dpa_to_region);
>  
>  	return ctx.cxlr;
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index 5ba606c6e03f..d0ed98a6bade 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -37,6 +37,13 @@ DECLARE_RWSEM(cxl_region_rwsem);
>  static DEFINE_IDA(cxl_port_ida);
>  static DEFINE_XARRAY(cxl_root_buses);
>  
> +int cxl_num_decoders_committed(struct cxl_port *port)
> +{
> +	lockdep_assert_held(&cxl_region_rwsem);
> +
> +	return port->commit_end + 1;
> +}
> +
>  static ssize_t devtype_show(struct device *dev, struct device_attribute *attr,
>  			    char *buf)
>  {
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 76d92561af29..36bd3f06dd90 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -679,6 +679,7 @@ static inline bool is_cxl_root(struct cxl_port *port)
>  	return port->uport_dev == port->dev.parent;
>  }
>  
> +int cxl_num_decoders_committed(struct cxl_port *port);
>  bool is_cxl_port(const struct device *dev);
>  struct cxl_port *to_cxl_port(const struct device *dev);
>  struct pci_bus;
> 
> 
> 

Re: [PATCH v3 2/2] cxl: Add decoders_committed sysfs attribute to cxl_port

[Jonathan Cameron]

On Mon, 16 Oct 2023 10:57:54 -0700
Dave Jiang <dave.jiang@intel.com> wrote:

> This attribute allows cxl-cli to determine whether there are decoders
> committed to a memdev.  This is only a snapshot of the state, and
> doesn't offer any protection or serialization against a concurrent
> disable-region operation.
> 
> Reviewed-by: Jim Harris <jim.harris@samsung.com>
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Seems reasonable, but it is adding ABI so the docs are missing.
Documentation/ABI/testing/sysfs-bus-cxl



> ---
> v2:
> - Use cxl_region_rwsem to protect reading of decoder info. (Dan)
> ---
>  drivers/cxl/core/port.c |   25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index d0ed98a6bade..0adee1e406ec 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -534,8 +534,33 @@ static void cxl_port_release(struct device *dev)
>  	kfree(port);
>  }
>  
> +static ssize_t decoders_committed_show(struct device *dev,
> +				       struct device_attribute *attr, char *buf)
> +{
> +	struct cxl_port *port = to_cxl_port(dev);
> +	int rc;
> +
> +	down_read(&cxl_region_rwsem);
> +	rc = sysfs_emit(buf, "%d\n", cxl_num_decoders_committed(port));
> +	up_read(&cxl_region_rwsem);
> +
> +	return rc;
> +}
> +
> +static DEVICE_ATTR_RO(decoders_committed);
> +
> +static struct attribute *cxl_port_attrs[] = {
> +	&dev_attr_decoders_committed.attr,
> +	NULL,
> +};
> +
> +static struct attribute_group cxl_port_attribute_group = {
> +	.attrs = cxl_port_attrs,
> +};
> +
>  static const struct attribute_group *cxl_port_attribute_groups[] = {
>  	&cxl_base_attribute_group,
> +	&cxl_port_attribute_group,
>  	NULL,
>  };
>  
> 
> 
> 

Re: [PATCH v3 1/2] cxl: Add cxl_decoders_committed() helper

[Alison Schofield]

On Mon, Oct 16, 2023 at 10:57:48AM -0700, Dave Jiang wrote:
> Add a helper to retrieve the number of decoders committed for the port.
> Replace all the open coding of the calculation with the helper.


Reviewed-by: Alison Schofield <alison.schofield@intel.com>

> 
> Link: https://lore.kernel.org/linux-cxl/651c98472dfed_ae7e729495@dwillia2-xfh.jf.intel.com.notmuch/
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> 
> ---
> v3:
> - Rename cxl_decoders_committed() to cxl_num_decoders_comitted() (Jim)
> - Compare cxl_num_decoders_committed() to 0 to improve readability (Jim)
> v2:
> - Remove EXPORT_SYMBOL() (Dan)
> - Rebase on top of Dan's Fix shutdown order series, to pick up
>   cxl_region_rwsem export.
> ---
>  drivers/cxl/core/hdm.c    |    7 ++++---
>  drivers/cxl/core/mbox.c   |    2 +-
>  drivers/cxl/core/memdev.c |    4 ++--
>  drivers/cxl/core/port.c   |    7 +++++++
>  drivers/cxl/cxl.h         |    1 +
>  5 files changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 506c9e14cdf9..7d112557c939 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -643,10 +643,11 @@ static int cxl_decoder_commit(struct cxl_decoder *cxld)
>  	if (cxld->flags & CXL_DECODER_F_ENABLE)
>  		return 0;
>  
> -	if (port->commit_end + 1 != id) {
> +	if (cxl_num_decoders_committed(port) != id) {
>  		dev_dbg(&port->dev,
>  			"%s: out of order commit, expected decoder%d.%d\n",
> -			dev_name(&cxld->dev), port->id, port->commit_end + 1);
> +			dev_name(&cxld->dev), port->id,
> +			cxl_num_decoders_committed(port));
>  		return -EBUSY;
>  	}
>  
> @@ -863,7 +864,7 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
>  			cxld->target_type = CXL_DECODER_HOSTONLYMEM;
>  		else
>  			cxld->target_type = CXL_DECODER_DEVMEM;
> -		if (cxld->id != port->commit_end + 1) {
> +		if (cxld->id != cxl_num_decoders_committed(port)) {
>  			dev_warn(&port->dev,
>  				 "decoder%d.%d: Committed out of order\n",
>  				 port->id, cxld->id);
> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> index 67aec57cc12f..04033b06f75f 100644
> --- a/drivers/cxl/core/mbox.c
> +++ b/drivers/cxl/core/mbox.c
> @@ -1200,7 +1200,7 @@ int cxl_mem_sanitize(struct cxl_memdev *cxlmd, u16 cmd)
>  	 * Require an endpoint to be safe otherwise the driver can not
>  	 * be sure that the device is unmapped.
>  	 */
> -	if (endpoint && endpoint->commit_end == -1)
> +	if (endpoint && cxl_num_decoders_committed(endpoint) == 0)
>  		rc = __cxl_mem_sanitize(mds, cmd);
>  	else
>  		rc = -EBUSY;
> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> index fed9573cf355..fc5c2b414793 100644
> --- a/drivers/cxl/core/memdev.c
> +++ b/drivers/cxl/core/memdev.c
> @@ -231,7 +231,7 @@ int cxl_trigger_poison_list(struct cxl_memdev *cxlmd)
>  	if (rc)
>  		return rc;
>  
> -	if (port->commit_end == -1) {
> +	if (cxl_num_decoders_committed(port) == 0) {
>  		/* No regions mapped to this memdev */
>  		rc = cxl_get_poison_by_memdev(cxlmd);
>  	} else {
> @@ -282,7 +282,7 @@ static struct cxl_region *cxl_dpa_to_region(struct cxl_memdev *cxlmd, u64 dpa)
>  		.dpa = dpa,
>  	};
>  	port = cxlmd->endpoint;
> -	if (port && is_cxl_endpoint(port) && port->commit_end != -1)
> +	if (port && is_cxl_endpoint(port) && cxl_num_decoders_committed(port))
>  		device_for_each_child(&port->dev, &ctx, __cxl_dpa_to_region);
>  
>  	return ctx.cxlr;
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index 5ba606c6e03f..d0ed98a6bade 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -37,6 +37,13 @@ DECLARE_RWSEM(cxl_region_rwsem);
>  static DEFINE_IDA(cxl_port_ida);
>  static DEFINE_XARRAY(cxl_root_buses);
>  
> +int cxl_num_decoders_committed(struct cxl_port *port)
> +{
> +	lockdep_assert_held(&cxl_region_rwsem);
> +
> +	return port->commit_end + 1;
> +}
> +
>  static ssize_t devtype_show(struct device *dev, struct device_attribute *attr,
>  			    char *buf)
>  {
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 76d92561af29..36bd3f06dd90 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -679,6 +679,7 @@ static inline bool is_cxl_root(struct cxl_port *port)
>  	return port->uport_dev == port->dev.parent;
>  }
>  
> +int cxl_num_decoders_committed(struct cxl_port *port);
>  bool is_cxl_port(const struct device *dev);
>  struct cxl_port *to_cxl_port(const struct device *dev);
>  struct pci_bus;
> 
> 

Re: [PATCH v3 2/2] cxl: Add decoders_committed sysfs attribute to cxl_port

[Dan Williams]

Jonathan Cameron wrote:
> On Mon, 16 Oct 2023 10:57:54 -0700
> Dave Jiang <dave.jiang@intel.com> wrote:
> 
> > This attribute allows cxl-cli to determine whether there are decoders
> > committed to a memdev.  This is only a snapshot of the state, and
> > doesn't offer any protection or serialization against a concurrent
> > disable-region operation.
> > 
> > Reviewed-by: Jim Harris <jim.harris@samsung.com>
> > Suggested-by: Dan Williams <dan.j.williams@intel.com>
> > Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> Seems reasonable, but it is adding ABI so the docs are missing.
> Documentation/ABI/testing/sysfs-bus-cxl

Agreed, folded in the following:

diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
index 087f762ebfd5..432610f41aee 100644
--- a/Documentation/ABI/testing/sysfs-bus-cxl
+++ b/Documentation/ABI/testing/sysfs-bus-cxl
@@ -178,6 +178,21 @@ Description:
                hardware decoder target list.
 
 
+What:          /sys/bus/cxl/devices/portX/decoders_committed
+Date:          October, 2023
+KernelVersion: v6.7
+Contact:       linux-cxl@vger.kernel.org
+Description:
+               (RO) A memory device is considered active when any of its
+               decoders are in the "committed" state (See CXL 3.0 8.2.4.19.7
+               CXL HDM Decoder n Control Register). Hotplug and destructive
+               operations like "sanitize" are blocked while device is actively
+               decoding a Host Physical Address range. Note that this number
+               may be elevated without any regionX objects active or even
+               enumerated, as this may be due to decoders established by
+               platform firwmare or a previous kernel (kexec).
+
+
 What:          /sys/bus/cxl/devices/decoderX.Y
 Date:          June, 2021
 KernelVersion: v5.14