> From: Yi Liu > Sent: Wednesday, March 8, 2023 9:29 PM > > This is another method to issue PCI hot reset for the users that bounds > device to a positive iommufd value. In such case, iommufd is a proof of > device ownership. By passing a zero-length fd array, user indicates kernel > to do ownership check with the bound iommufd. All the opened devices > within > the affected dev_set should have been bound to the same iommufd. This is > simpler and faster as user does not need to pass a set of fds and kernel > no need to search the device within the given fds. > > Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx> > Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx> I think you also need a s-o-b from Jason since he wrote most of the code here. > +struct iommufd_ctx *vfio_iommufd_physical_ctx(struct vfio_device *vdev) > +{ > + /* Only serve for physical device */ > + if (!vdev->iommufd_device) > + return NULL; pointless comment > --- a/include/uapi/linux/vfio.h > +++ b/include/uapi/linux/vfio.h > @@ -682,6 +682,11 @@ struct vfio_pci_hot_reset_info { > * The ownership can be proved by: > * - An array of group fds > * - An array of device fds > + * - A zero-length array > + * > + * In the last case all affected devices which are opened by this user > + * must have been bound to a same iommufd_ctx. This approach is only > + * available for devices bound to positive iommufd. As we chatted before I still think the last sentence is pointless. If a device is bound to negative iommufd value (i.e. noiommu) it doesn't have a valid iommufd_ctx so won't meet "bound to a same iommufd_ctx".