On Fri, Nov 25, 2022 at 04:57:27PM +0800, Yi Liu wrote:
> > +static int vfio_device_group_open(struct vfio_device *device)
> > +{
> > + int ret;
> > +
> > + mutex_lock(&device->group->group_lock);
>
> now the group path holds group_lock first, and then device_set->lock.
> this is different with existing code. is it acceptable? I had a quick
> check with this change, basic test is good. no a-b-b-a locking issue.
I looked for a while and couldn't find a reason why it wouldn't be OK
> > + if (!vfio_group_has_iommu(device->group)) {
> > + ret = -EINVAL;
> > + goto out_unlock;
> > + }
> > +
> > + /*
> > + * Here we pass the KVM pointer with the group under the lock. If the
> > + * device driver will use it, it must obtain a reference and release it
> > + * during close_device.
> > + */
> > + ret = vfio_device_open(device, device->group->iommufd,
> > + device->group->kvm);
> > +
> > +out_unlock:
> > + mutex_unlock(&device->group->group_lock);
> > + return ret;
> > +}
> > +
> > +void vfio_device_close_group(struct vfio_device *device)
> > +{
> > + mutex_lock(&device->group->group_lock);
> > + vfio_device_close(device, device->group->iommufd);
> > + mutex_unlock(&device->group->group_lock);
> > +}
> > +
>
> above two functions should be put in group.c.
Yes
Jason
