Re: [PATCH v3 2/3] cxl: Fix sysfs export of qos_class for memdev

[Dave Jiang <dave.jiang@intel.com>]

On 2/5/24 4:40 AM, Jonathan Cameron wrote:
> On Thu, 1 Feb 2024 14:47:30 -0700
> Dave Jiang <dave.jiang@intel.com> wrote:
> 
>> Current implementation exports only to
>> /sys/bus/cxl/devices/.../memN/qos_class. With both ram and pmem exposed,
>> the second registered sysfs attribute is rejected as duplicate. It's not
>> possible to create qos_class under the dev_groups via the driver due to
>> the ram and pmem sysfs sub-directories already created by the device sysfs
>> groups. Move the ram and pmem qos_class to the device sysfs groups and add
>> a call to sysfs_update() after the perf data are validated so the
>> qos_class can be visible. The end results should be
>> /sys/bus/cxl/devices/.../memN/ram/qos_class and
>> /sys/bus/cxl/devices/.../memN/pmem/qos_class.
>>
>> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> Some comments inline.  Only think I really care about though is a comment
> in the code to say why sysfs_update_groups() is not appropriate.

Didn't realize that helper existed. I'll move over to using that. 
DJ

> 
>> ---
>> v3:
>> - Updated based on pervious patch changes
>> ---
>>  drivers/cxl/core/cdat.c   |  1 +
>>  drivers/cxl/core/memdev.c | 71 +++++++++++++++++++++++++++++++++++++++
>>  drivers/cxl/cxl.h         |  2 ++
>>  drivers/cxl/mem.c         | 36 --------------------
>>  4 files changed, 74 insertions(+), 36 deletions(-)
>>
>> diff --git a/drivers/cxl/core/cdat.c b/drivers/cxl/core/cdat.c
>> index 55b82dfd794b..5c93bf9d5253 100644
>> --- a/drivers/cxl/core/cdat.c
>> +++ b/drivers/cxl/core/cdat.c
>> @@ -382,6 +382,7 @@ void cxl_endpoint_parse_cdat(struct cxl_port *port)
>>  
>>  	cxl_memdev_set_qos_class(cxlds, dsmas_xa);
>>  	cxl_qos_class_verify(cxlmd);
>> +	cxl_memdev_update_attribute_groups(cxlmd);
>>  }
>>  EXPORT_SYMBOL_NS_GPL(cxl_endpoint_parse_cdat, CXL);
>>  
>> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
>> index dae8802ecdb0..ed85096a33fb 100644
>> --- a/drivers/cxl/core/memdev.c
>> +++ b/drivers/cxl/core/memdev.c
>> @@ -447,13 +447,41 @@ static struct attribute *cxl_memdev_attributes[] = {
>>  	NULL,
>>  };
>>  
>> +static ssize_t pmem_qos_class_show(struct device *dev,
>> +				   struct device_attribute *attr, char *buf)
>> +{
>> +	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
>> +	struct cxl_dev_state *cxlds = cxlmd->cxlds;
>> +	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlds);
>> +
>> +	return sysfs_emit(buf, "%d\n", mds->pmem_perf.qos_class);
>> +}
>> +
>> +static struct device_attribute dev_attr_pmem_qos_class =
>> +	__ATTR(qos_class, 0444, pmem_qos_class_show, NULL);
>> +
>>  static struct attribute *cxl_memdev_pmem_attributes[] = {
>>  	&dev_attr_pmem_size.attr,
>> +	&dev_attr_pmem_qos_class.attr,
>>  	NULL,
>>  };
>>  
>> +static ssize_t ram_qos_class_show(struct device *dev,
>> +				  struct device_attribute *attr, char *buf)
>> +{
>> +	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
>> +	struct cxl_dev_state *cxlds = cxlmd->cxlds;
>> +	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlds);
>> +
>> +	return sysfs_emit(buf, "%d\n", mds->ram_perf.qos_class);
>> +}
>> +
>> +static struct device_attribute dev_attr_ram_qos_class =
>> +	__ATTR(qos_class, 0444, ram_qos_class_show, NULL);
>> +
>>  static struct attribute *cxl_memdev_ram_attributes[] = {
>>  	&dev_attr_ram_size.attr,
>> +	&dev_attr_ram_qos_class.attr,
>>  	NULL,
>>  };
>>  
>> @@ -477,14 +505,42 @@ static struct attribute_group cxl_memdev_attribute_group = {
>>  	.is_visible = cxl_memdev_visible,
>>  };
>>  
>> +static umode_t cxl_ram_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);
>> +
>> +	if (a == &dev_attr_ram_qos_class.attr)
>> +		if (mds->ram_perf.qos_class == CXL_QOS_CLASS_INVALID)
>> +			return 0;
>> +
>> +	return a->mode;
>> +}
>> +
>>  static struct attribute_group cxl_memdev_ram_attribute_group = {
>>  	.name = "ram",
>>  	.attrs = cxl_memdev_ram_attributes,
>> +	.is_visible = cxl_ram_visible,
>>  };
>>  
>> +static umode_t cxl_pmem_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);
>> +
>> +	if (a == &dev_attr_pmem_qos_class.attr)
>> +		if (mds->pmem_perf.qos_class == CXL_QOS_CLASS_INVALID)
>> +			return 0;
>> +
>> +	return a->mode;
>> +}
>> +
>>  static struct attribute_group cxl_memdev_pmem_attribute_group = {
>>  	.name = "pmem",
>>  	.attrs = cxl_memdev_pmem_attributes,
>> +	.is_visible = cxl_pmem_visible,
>>  };
>>  
>>  static umode_t cxl_memdev_security_visible(struct kobject *kobj,
>> @@ -519,6 +575,21 @@ static const struct attribute_group *cxl_memdev_attribute_groups[] = {
>>  	NULL,
>>  };
>>  
>> +void cxl_memdev_update_attribute_groups(struct cxl_memdev *cxlmd)
>> +{
>> +	const struct attribute_group *grp = cxl_memdev_attribute_groups[0];
>> +
>> +	for (int i = 0; grp; i++) {
>> +		int rc = sysfs_update_group(&cxlmd->dev.kobj, grp);
>> +
>> +		if (rc)
>> +			dev_dbg(&cxlmd->dev,
>> +				"Unable to update memdev attribute group.\n");
>> +		grp = cxl_memdev_attribute_groups[i + 1];
> We don't need i explicitly so maybe cleaner as something like.
> 
> 	for (const struct attribute_group **grp = &cxl_memdev_attribute_groups[0];
> 	     grp; grp++)
> 		if (sysfs_update_group(&cxlmd->dev.kobj, *grp)
> 			dev_dbg(....)
> 
> Mind you I'm not that convinced, so fine if you want to stick with current code :)
> 
> I'd also like a comment on why sysfs_update_groups() is not appropriate here.
> 
>> +	}
>> +}
>> +EXPORT_SYMBOL_NS_GPL(cxl_memdev_update_attribute_groups, CXL);
>> +
>>  static const struct device_type cxl_memdev_type = {
>>  	.name = "cxl_memdev",
>>  	.release = cxl_memdev_release,
> 
>>  
>