Re: [PATCH 03/13] vfio: Provide better generic support for open/release vfio_device_ops

From: Jason Gunthorpe <jgg@nvidia.com>
To: Cornelia Huck <cohuck@redhat.com>
Cc: David Airlie <airlied@linux.ie>,
	Tony Krowiak <akrowiak@linux.ibm.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Jonathan Corbet <corbet@lwn.net>, Daniel Vetter <daniel@ffwll.ch>,
	Diana Craciun <diana.craciun@oss.nxp.com>,
	dri-devel@lists.freedesktop.org,
	Eric Auger <eric.auger@redhat.com>,
	Eric Farman <farman@linux.ibm.com>,
	Harald Freudenberger <freude@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	intel-gfx@lists.freedesktop.org,
	intel-gvt-dev@lists.freedesktop.org,
	Jani Nikula <jani.nikula@linux.intel.com>,
	Jason Herne <jjherne@linux.ibm.com>,
	Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	kvm@vger.kernel.org, Kirti Wankhede <kwankhede@nvidia.com>,
	linux-doc@vger.kernel.org, linux-s390@vger.kernel.org,
	Matthew Rosato <mjrosato@linux.ibm.com>,
	Peter Oberparleiter <oberpar@linux.ibm.com>,
	Halil Pasic <pasic@linux.ibm.com>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	Vineeth Vijayan <vneethv@linux.ibm.com>,
	Zhenyu Wang <zhenyuw@linux.intel.com>,
	Zhi Wang <zhi.a.wang@intel.com>,
	"Raj, Ashok" <ashok.raj@intel.com>,
	Christoph Hellwig <hch@lst.de>,
	Leon Romanovsky <leonro@nvidia.com>,
	Max Gurtovoy <mgurtovoy@nvidia.com>,
	Yishai Hadas <yishaih@nvidia.com>
Subject: Re: [PATCH 03/13] vfio: Provide better generic support for open/release vfio_device_ops
Date: Mon, 19 Jul 2021 10:01:31 -0300	[thread overview]
Message-ID: <20210719130131.GQ543781@nvidia.com> (raw)
In-Reply-To: <87wnpma299.fsf@redhat.com>

On Mon, Jul 19, 2021 at 02:58:58PM +0200, Cornelia Huck wrote:
> > -	ret = device->ops->open(device);
> > -	if (ret) {
> > -		module_put(device->dev->driver->owner);
> > -		vfio_device_put(device);
> > -		return ret;
> > +	mutex_lock(&device->dev_set->lock);
> > +	device->open_count++;
> > +	if (device->open_count == 1 && device->ops->open_device) {
> > +		ret = device->ops->open_device(device);
> > +		if (ret)
> > +			goto err_undo_count;
> 
> Won't that fail for mdev devices, until the patches later in this series
> have been applied? (i.e. bad for bisect)

What are you seeing? At this point all devices will have a NULL
open_device and skip this logic?

Jason