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

Kirti Wankhede
2022-06-06T20:02:46Z

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);
> };
>