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

[Eric Farman <farman@linux.ibm.com>]

On Tue, 2022-06-07 at 01:32 +0530, Kirti Wankhede wrote:
> 
> 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.

Apologies. This series was fit to 5.18 as the merge window progressed.
Both this patch and the previous one have to adjust to the removal of
mdev_parent_ops that came about from 

commit 6b42f491e17ce13f5ff7f2d1f49c73a0f4c47b20
Author: Jason Gunthorpe <jgg@ziepe.ca>
Date:   Mon Apr 11 16:14:01 2022 +0200

    vfio/mdev: Remove mdev_parent_ops

I have this rebased for v2.

Eric

> 
> 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);
> >   };
> >