Re: [PATCH v1 14/18] vfio/mdev: Add mdev available instance checking to the core

[Kirti Wankhede <kwankhede@nvidia.com>]

On 6/2/2022 10:49 PM, Eric Farman wrote:
> From: Jason Gunthorpe <jgg@nvidia.com>
> 
> Many of the mdev drivers use a simple counter for keeping track of the
> available instances. Move this code to the core code and store the counter
> in the mdev_type. Implement it using correct locking, fixing mdpy.
> 
> Drivers provide a get_available() callback to set the number of available
> instances for their mtypes which is fixed at registration time. The core
> provides a standard sysfs attribute to return the available_instances.
> 
> Cc: Kirti Wankhede <kwankhede@nvidia.com>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Tony Krowiak <akrowiak@linux.ibm.com>
> Cc: Jason Herne <jjherne@linux.ibm.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> Link: https://lore.kernel.org/r/7-v3-57c1502c62fd+2190-ccw_mdev_jgg@nvidia.com/
> [farman: added Cc: tags]
> Signed-off-by: Eric Farman <farman@linux.ibm.com>
> ---
>   .../driver-api/vfio-mediated-device.rst       |  4 +-
>   drivers/s390/cio/vfio_ccw_drv.c               |  1 -
>   drivers/s390/cio/vfio_ccw_ops.c               | 26 ++++---------
>   drivers/s390/cio/vfio_ccw_private.h           |  2 -
>   drivers/s390/crypto/vfio_ap_ops.c             | 32 ++++------------
>   drivers/s390/crypto/vfio_ap_private.h         |  2 -
>   drivers/vfio/mdev/mdev_core.c                 | 11 +++++-
>   drivers/vfio/mdev/mdev_private.h              |  2 +
>   drivers/vfio/mdev/mdev_sysfs.c                | 37 +++++++++++++++++++
>   include/linux/mdev.h                          |  2 +
>   samples/vfio-mdev/mdpy.c                      | 22 +++--------
>   11 files changed, 76 insertions(+), 65 deletions(-)
> 
> diff --git a/Documentation/driver-api/vfio-mediated-device.rst b/Documentation/driver-api/vfio-mediated-device.rst
> index f410a1cd98bb..a4f7f1362fa8 100644
> --- a/Documentation/driver-api/vfio-mediated-device.rst
> +++ b/Documentation/driver-api/vfio-mediated-device.rst
> @@ -106,6 +106,7 @@ structure to represent a mediated device's driver::
>   	     int  (*probe)  (struct mdev_device *dev);
>   	     void (*remove) (struct mdev_device *dev);
>   	     struct device_driver    driver;
> +	     unsigned int (*get_available)(struct mdev_type *mtype);
>        };
>

This patch conflicts with Christoph Hellwig's patch. I see 
'supported_type_groups' is not is above structure, I beleive that your 
patch is applied on top of Christoph's patch series.

but then in below part of code, 'add_mdev_supported_type' has also being 
removed in Christoph's patch. So this patch would not get applied cleanly.

Thanks,
Kirti

> +/* mdev_type attribute used by drivers that have an get_available() op */
> +static ssize_t available_instances_show(struct mdev_type *mtype,
> +					struct mdev_type_attribute *attr,
> +					char *buf)
> +{
> +	unsigned int available;
> +
> +	mutex_lock(&mdev_list_lock);
> +	available = mtype->available;
> +	mutex_unlock(&mdev_list_lock);
> +
> +	return sysfs_emit(buf, "%u\n", available);
> +}
> +static MDEV_TYPE_ATTR_RO(available_instances);
> +static umode_t available_instances_is_visible(struct kobject *kobj,
> +					      struct attribute *attr, int n)
> +{
> +	struct mdev_type *type = to_mdev_type(kobj);
> +
> +	if (!type->parent->ops->device_driver->get_available)
> +		return 0;
> +	return attr->mode;
> +}
> +static struct attribute *mdev_types_name_attrs[] = {
> +	&mdev_type_attr_available_instances.attr,
> +	NULL,
> +};
> +static struct attribute_group mdev_type_available_instances_group = {
> +	.attrs = mdev_types_name_attrs,
> +	.is_visible = available_instances_is_visible,
> +};
> +
>   static const struct attribute_group *mdev_type_groups[] = {
>   	&mdev_type_std_group,
> +	&mdev_type_available_instances_group,
>   	NULL,
>   };
>   
> @@ -136,6 +169,10 @@ static struct mdev_type *add_mdev_supported_type(struct mdev_parent *parent,
>   	mdev_get_parent(parent);
>   	type->type_group_id = type_group_id;
>   
> +	if (parent->ops->device_driver->get_available)
> +		type->available =
> +			parent->ops->device_driver->get_available(type);
> +
>   	ret = kobject_init_and_add(&type->kobj, &mdev_type_ktype, NULL,
>   				   "%s-%s", dev_driver_string(parent->dev),
>   				   group->name);
> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> index 14655215417b..0ce1bb3dabd0 100644
> --- a/include/linux/mdev.h
> +++ b/include/linux/mdev.h
> @@ -120,12 +120,14 @@ struct mdev_type_attribute {
>    * @probe: called when new device created
>    * @remove: called when device removed
>    * @driver: device driver structure
> + * @get_available: Return the max number of instances that can be created
>    *
>    **/
>   struct mdev_driver {
>   	int (*probe)(struct mdev_device *dev);
>   	void (*remove)(struct mdev_device *dev);
>   	struct device_driver driver;
> +	unsigned int (*get_available)(struct mdev_type *mtype);
>   };
>