Re: [PATCH RFC v2 07/18] cxl/mem: Expose device dynamic capacity configuration

[Fan Ni]

On Tue, Aug 29, 2023 at 04:14:49PM +0100, Jonathan Cameron wrote:
> On Mon, 28 Aug 2023 22:20:58 -0700
> ira.weiny@xxxxxxxxx wrote:
>
> > From: Navneet Singh <navneet.singh@xxxxxxxxx>
> >
> > To properly configure CXL regions on Dynamic Capacity Devices (DCD),
> > user space will need to know the details of the DC Regions available on
> > a device.
> >
> > Expose driver dynamic capacity configuration through sysfs
> > attributes.
> >
> > Co-developed-by: Navneet Singh <navneet.singh@xxxxxxxxx>
> > Signed-off-by: Navneet Singh <navneet.singh@xxxxxxxxx>
> > Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
> >
> One trivial comment inline.  I wondered a bit if it would
> be better to not present dc at all on devices that don't support
> dynamic capacity, but for now there isn't an elegant way to do that
> (some discussions and patches are flying around however so maybe this
>  will be resolved before this series merges giving us that elegant
>  option).
>
> With commented code tidied up
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
>

Agreed. It makes more sense to not show dc at all.
Other than that, looks good to me.

Reviewed-by: Fan Ni <fan.ni@xxxxxxxxxxx>

>
> > ---
> > Changes for v2:
> > [iweiny: Rebased on latest master/type2 work]
> > [iweiny: add documentation for sysfs entries]
> > [iweiny: s/dc_regions_count/region_count/]
> > [iweiny: s/dcY_size/regionY_size/]
> > [alison: change size format to %#llx]
> > [iweiny: change count format to %d]
> > [iweiny: Formatting updates]
> > [iweiny: Fix crash when device is not a mem device: found with cxl-test]
> > ---
> >  Documentation/ABI/testing/sysfs-bus-cxl | 17 ++++++++
> >  drivers/cxl/core/memdev.c               | 77 +++++++++++++++++++++++++++++++++
> >  2 files changed, 94 insertions(+)
> >
> > diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
> > index 2268ffcdb604..aa65dc5b4e13 100644
> > --- a/Documentation/ABI/testing/sysfs-bus-cxl
> > +++ b/Documentation/ABI/testing/sysfs-bus-cxl
> > @@ -37,6 +37,23 @@ Description:
> >  		identically named field in the Identify Memory Device Output
> >  		Payload in the CXL-2.0 specification.
> >
> > +What:		/sys/bus/cxl/devices/memX/dc/region_count
> > +Date:		July, 2023
> > +KernelVersion:	v6.6
> > +Contact:	linux-cxl@xxxxxxxxxxxxxxx
> > +Description:
> > +		(RO) Number of Dynamic Capacity (DC) regions supported on the
> > +		device.  May be 0 if the device does not support Dynamic
> > +		Capacity.
> > +
> > +What:		/sys/bus/cxl/devices/memX/dc/regionY_size
> > +Date:		July, 2023
> > +KernelVersion:	v6.6
> > +Contact:	linux-cxl@xxxxxxxxxxxxxxx
> > +Description:
> > +		(RO) Size of the Dynamic Capacity (DC) region Y.  Only
> > +		available on devices which support DC and only for those
> > +		region indexes supported by the device.
> >
> >  What:		/sys/bus/cxl/devices/memX/serial
> >  Date:		January, 2022
> > diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> > index 492486707fd0..397262e0ebd2 100644
> > --- a/drivers/cxl/core/memdev.c
> > +++ b/drivers/cxl/core/memdev.c
> > @@ -101,6 +101,20 @@ static ssize_t pmem_size_show(struct device *dev, struct device_attribute *attr,
> >  static struct device_attribute dev_attr_pmem_size =
> >  	__ATTR(size, 0444, pmem_size_show, NULL);
> >
> > +static ssize_t region_count_show(struct device *dev, struct device_attribute *attr,
> > +				 char *buf)
> > +{
> > +	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
> > +	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlmd->cxlds);
> > +	int len = 0;
> > +
> > +	len = sysfs_emit(buf, "%d\n", mds->nr_dc_region);
> > +	return len;
>
> return sysfs_emit(buf, "...);
>
> > +}
> > +
> > +struct device_attribute dev_attr_region_count =
> > +	__ATTR(region_count, 0444, region_count_show, NULL);
> > +
> >  static ssize_t serial_show(struct device *dev, struct device_attribute *attr,
> >  			   char *buf)
> >  {
> > @@ -454,6 +468,62 @@ static struct attribute *cxl_memdev_security_attributes[] = {
> >  	NULL,
> >  };
> >
> > +static ssize_t show_size_regionN(struct cxl_memdev *cxlmd, char *buf, int pos)
> > +{
> > +	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlmd->cxlds);
> > +
> > +	return sysfs_emit(buf, "%#llx\n", mds->dc_region[pos].decode_len);
> > +}
> > +
> > +#define REGION_SIZE_ATTR_RO(n)						\
> > +static ssize_t region##n##_size_show(struct device *dev,		\
> > +				     struct device_attribute *attr,	\
> > +				     char *buf)				\
> > +{									\
> > +	return show_size_regionN(to_cxl_memdev(dev), buf, (n));		\
> > +}									\
> > +static DEVICE_ATTR_RO(region##n##_size)
> > +REGION_SIZE_ATTR_RO(0);
> > +REGION_SIZE_ATTR_RO(1);
> > +REGION_SIZE_ATTR_RO(2);
> > +REGION_SIZE_ATTR_RO(3);
> > +REGION_SIZE_ATTR_RO(4);
> > +REGION_SIZE_ATTR_RO(5);
> > +REGION_SIZE_ATTR_RO(6);
> > +REGION_SIZE_ATTR_RO(7);
> > +
> > +static struct attribute *cxl_memdev_dc_attributes[] = {
> > +	&dev_attr_region0_size.attr,
> > +	&dev_attr_region1_size.attr,
> > +	&dev_attr_region2_size.attr,
> > +	&dev_attr_region3_size.attr,
> > +	&dev_attr_region4_size.attr,
> > +	&dev_attr_region5_size.attr,
> > +	&dev_attr_region6_size.attr,
> > +	&dev_attr_region7_size.attr,
> > +	&dev_attr_region_count.attr,
> > +	NULL,
> > +};
> > +
> > +static umode_t cxl_dc_visible(struct kobject *kobj, struct attribute *a, int n)
> > +{
> > +	struct device *dev = kobj_to_dev(kobj);
> > +	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
> > +	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlmd->cxlds);
> > +
> > +	/* Not a memory device */
> > +	if (!mds)
> > +		return 0;
> > +
> > +	if (a == &dev_attr_region_count.attr)
> > +		return a->mode;
> > +
> > +	if (n < mds->nr_dc_region)
> > +		return a->mode;
> > +
> > +	return 0;
> > +}
> > +
> >  static umode_t cxl_memdev_visible(struct kobject *kobj, struct attribute *a,
> >  				  int n)
> >  {
> > @@ -482,11 +552,18 @@ static struct attribute_group cxl_memdev_security_attribute_group = {
> >  	.attrs = cxl_memdev_security_attributes,
> >  };
> >
> > +static struct attribute_group cxl_memdev_dc_attribute_group = {
> > +	.name = "dc",
> > +	.attrs = cxl_memdev_dc_attributes,
> > +	.is_visible = cxl_dc_visible,
> > +};
> > +
> >  static const struct attribute_group *cxl_memdev_attribute_groups[] = {
> >  	&cxl_memdev_attribute_group,
> >  	&cxl_memdev_ram_attribute_group,
> >  	&cxl_memdev_pmem_attribute_group,
> >  	&cxl_memdev_security_attribute_group,
> > +	&cxl_memdev_dc_attribute_group,
> >  	NULL,
> >  };
> >
> >
>