> From: Matthew Rosato
> Sent: Thursday, May 19, 2022 5:26 AM
>
> Rather than relying on a notifier for associating the KVM with
> the group, let's assume that the association has already been
> made prior to device_open. The first time a device is opened
> associate the group KVM with the device.
>
> This fixes a user-triggerable oops in GVT.
No changelog.
>
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Signed-off-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
Not sure whether Christoph wants a s-o-b here when he wrote
the snippet to remove the release work of gvt...
> @@ -1083,11 +1083,22 @@ static struct file *vfio_device_open(struct
> vfio_device *device)
>
> mutex_lock(&device->dev_set->lock);
> device->open_count++;
> + down_read(&device->group->group_rwsem);
> + if (device->open_count == 1 && device->group->kvm) {
> + /*
> + * Here we pass the KVM pointer with the group under the
> read
> + * lock. If the device driver will use it, it must obtain a
> + * reference and release it during close_device.
> + */
> + device->kvm = device->group->kvm;
> + }
> +
> if (device->open_count == 1 && device->ops->open_device) {
Merge the two branches so both are under if (device->open_count == 1) {}
(and group_rwsem can be also moved inside)
> @@ -1315,9 +1330,13 @@ static int vfio_device_fops_release(struct inode
> *inode, struct file *filep)
>
> mutex_lock(&device->dev_set->lock);
> vfio_assert_device_open(device);
> + down_read(&device->group->group_rwsem);
> if (device->open_count == 1 && device->ops->close_device)
> device->ops->close_device(device);
> device->open_count--;
> + if (device->open_count == 0 && device->kvm)
> + device->kvm = NULL;
This can be moved out of group_rwsem as there is no reference to
vfio_group.
> + up_read(&device->group->group_rwsem);
otherwise,
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
Thanks
Kevin
