Re: [PATCH 05/18] cxl/region: Add volatile region creation support

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Sun, 05 Feb 2023 17:02:56 -0800
Dan Williams <dan.j.williams@intel.com> wrote:

> Expand the region creation infrastructure to enable 'ram'
> (volatile-memory) regions. The internals of create_pmem_region_store()
> and create_pmem_region_show() are factored out into helpers
> __create_region() and __create_region_show() for the 'ram' case to
> reuse.
> 
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Entirely trivial comments inline.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  Documentation/ABI/testing/sysfs-bus-cxl |   22 +++++-----
>  drivers/cxl/core/core.h                 |    1 
>  drivers/cxl/core/port.c                 |   14 ++++++
>  drivers/cxl/core/region.c               |   71 +++++++++++++++++++++++++------
>  4 files changed, 82 insertions(+), 26 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
> index 4c4e1cbb1169..3acf2f17a73f 100644
> --- a/Documentation/ABI/testing/sysfs-bus-cxl
> +++ b/Documentation/ABI/testing/sysfs-bus-cxl
> @@ -285,20 +285,20 @@ Description:
>  		interleave_granularity).
>  
>  
> -What:		/sys/bus/cxl/devices/decoderX.Y/create_pmem_region
> -Date:		May, 2022
> -KernelVersion:	v6.0
> +What:		/sys/bus/cxl/devices/decoderX.Y/create_{pmem,ram}_region
> +Date:		May, 2022, January, 2023
> +KernelVersion:	v6.0 (pmem), v6.3 (ram)
>  Contact:	linux-cxl@vger.kernel.org
>  Description:
>  		(RW) Write a string in the form 'regionZ' to start the process
> -		of defining a new persistent memory region (interleave-set)
> -		within the decode range bounded by root decoder 'decoderX.Y'.
> -		The value written must match the current value returned from
> -		reading this attribute. An atomic compare exchange operation is
> -		done on write to assign the requested id to a region and
> -		allocate the region-id for the next creation attempt. EBUSY is
> -		returned if the region name written does not match the current
> -		cached value.
> +		of defining a new persistent, or volatile memory region
> +		(interleave-set) within the decode range bounded by root decoder
> +		'decoderX.Y'. The value written must match the current value
> +		returned from reading this attribute. An atomic compare exchange
> +		operation is done on write to assign the requested id to a
> +		region and allocate the region-id for the next creation attempt.
> +		EBUSY is returned if the region name written does not match the
> +		current cached value.
>  
>  
>  What:		/sys/bus/cxl/devices/decoderX.Y/delete_region
> diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
> index 8c04672dca56..5eb873da5a30 100644
> --- a/drivers/cxl/core/core.h
> +++ b/drivers/cxl/core/core.h
> @@ -11,6 +11,7 @@ extern struct attribute_group cxl_base_attribute_group;
>  
>  #ifdef CONFIG_CXL_REGION
>  extern struct device_attribute dev_attr_create_pmem_region;
> +extern struct device_attribute dev_attr_create_ram_region;
>  extern struct device_attribute dev_attr_delete_region;
>  extern struct device_attribute dev_attr_region;
>  extern const struct device_type cxl_pmem_region_type;
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index 8566451cb22f..47e450c3a5a9 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -294,6 +294,7 @@ static struct attribute *cxl_decoder_root_attrs[] = {
>  	&dev_attr_cap_type3.attr,
>  	&dev_attr_target_list.attr,
>  	SET_CXL_REGION_ATTR(create_pmem_region)
> +	SET_CXL_REGION_ATTR(create_ram_region)
>  	SET_CXL_REGION_ATTR(delete_region)
>  	NULL,
>  };
> @@ -305,6 +306,13 @@ static bool can_create_pmem(struct cxl_root_decoder *cxlrd)
>  	return (cxlrd->cxlsd.cxld.flags & flags) == flags;
>  }
>  
> +static bool can_create_ram(struct cxl_root_decoder *cxlrd)
> +{
> +	unsigned long flags = CXL_DECODER_F_TYPE3 | CXL_DECODER_F_RAM;
> +
> +	return (cxlrd->cxlsd.cxld.flags & flags) == flags;
> +}
> +
>  static umode_t cxl_root_decoder_visible(struct kobject *kobj, struct attribute *a, int n)
>  {
>  	struct device *dev = kobj_to_dev(kobj);
> @@ -313,7 +321,11 @@ static umode_t cxl_root_decoder_visible(struct kobject *kobj, struct attribute *
>  	if (a == CXL_REGION_ATTR(create_pmem_region) && !can_create_pmem(cxlrd))
>  		return 0;
>  
> -	if (a == CXL_REGION_ATTR(delete_region) && !can_create_pmem(cxlrd))
> +	if (a == CXL_REGION_ATTR(create_ram_region) && !can_create_ram(cxlrd))
> +		return 0;
> +
> +	if (a == CXL_REGION_ATTR(delete_region) &&
> +	    !(can_create_pmem(cxlrd) || can_create_ram(cxlrd)))
>  		return 0;
>  
>  	return a->mode;
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 53d6dbe4de6d..8dea49c021b8 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -1685,6 +1685,15 @@ static struct cxl_region *devm_cxl_add_region(struct cxl_root_decoder *cxlrd,
>  	struct device *dev;
>  	int rc;
>  
> +	switch (mode) {
> +	case CXL_DECODER_RAM:
> +	case CXL_DECODER_PMEM:
> +		break;
> +	default:
> +		dev_err(&cxlrd->cxlsd.cxld.dev, "unsupported mode %d\n", mode);
> +		return ERR_PTR(-EINVAL);
> +	}
> +
>  	cxlr = cxl_region_alloc(cxlrd, id);
>  	if (IS_ERR(cxlr))
>  		return cxlr;
> @@ -1713,12 +1722,38 @@ static struct cxl_region *devm_cxl_add_region(struct cxl_root_decoder *cxlrd,
>  	return ERR_PTR(rc);
>  }
>  
> +static ssize_t __create_region_show(struct cxl_root_decoder *cxlrd, char *buf)
> +{
> +	return sysfs_emit(buf, "region%u\n", atomic_read(&cxlrd->region_id));
> +}
> +
>  static ssize_t create_pmem_region_show(struct device *dev,
>  				       struct device_attribute *attr, char *buf)
>  {
> -	struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(dev);
> +	return __create_region_show(to_cxl_root_decoder(dev), buf);
> +}
>  
> -	return sysfs_emit(buf, "region%u\n", atomic_read(&cxlrd->region_id));
> +static ssize_t create_ram_region_show(struct device *dev,
> +				      struct device_attribute *attr, char *buf)
> +{
> +	return __create_region_show(to_cxl_root_decoder(dev), buf);
> +}
> +
> +static struct cxl_region *__create_region(struct cxl_root_decoder *cxlrd,
> +					  enum cxl_decoder_mode mode, int id)
> +{
> +	int rc;
> +
> +	rc = memregion_alloc(GFP_KERNEL);
> +	if (rc < 0)
> +		return ERR_PTR(rc);
> +
> +	if (atomic_cmpxchg(&cxlrd->region_id, id, rc) != id) {
> +		memregion_free(rc);
> +		return ERR_PTR(-EBUSY);
> +	}
> +
> +	return devm_cxl_add_region(cxlrd, id, mode, CXL_DECODER_EXPANDER);
>  }
>  
>  static ssize_t create_pmem_region_store(struct device *dev,
> @@ -1727,29 +1762,37 @@ static ssize_t create_pmem_region_store(struct device *dev,
>  {
>  	struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(dev);
>  	struct cxl_region *cxlr;
> -	int id, rc;
> +	int rc, id;
>  
>  	rc = sscanf(buf, "region%d\n", &id);
>  	if (rc != 1)
>  		return -EINVAL;
>  
> -	rc = memregion_alloc(GFP_KERNEL);
> -	if (rc < 0)
> -		return rc;
> +	cxlr = __create_region(cxlrd, CXL_DECODER_PMEM, id);
> +	if (IS_ERR(cxlr))
> +		return PTR_ERR(cxlr);

I'd have a blank line here - see below.

> +	return len;
> +}
> +DEVICE_ATTR_RW(create_pmem_region);
>  
> -	if (atomic_cmpxchg(&cxlrd->region_id, id, rc) != id) {
> -		memregion_free(rc);
> -		return -EBUSY;
> -	}
> +static ssize_t create_ram_region_store(struct device *dev,
> +				       struct device_attribute *attr,
> +				       const char *buf, size_t len)
> +{
> +	struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(dev);
> +	struct cxl_region *cxlr;
> +	int rc, id;
>  
> -	cxlr = devm_cxl_add_region(cxlrd, id, CXL_DECODER_PMEM,
> -				   CXL_DECODER_EXPANDER);
> +	rc = sscanf(buf, "region%d\n", &id);
> +	if (rc != 1)
> +		return -EINVAL;
> +
> +	cxlr = __create_region(cxlrd, CXL_DECODER_RAM, id);
>  	if (IS_ERR(cxlr))
>  		return PTR_ERR(cxlr);
> -

Just so you know I read to the end!

Spurious unrelated white space change :)

>  	return len;
>  }
> -DEVICE_ATTR_RW(create_pmem_region);
> +DEVICE_ATTR_RW(create_ram_region);
>  
>  static ssize_t region_show(struct device *dev, struct device_attribute *attr,
>  			   char *buf)
>