On Wed, Dec 3, 2025 at 7:55 AM Alex Mastro <[email protected]> wrote:
>
> On Wed, Nov 26, 2025 at 07:35:53PM +0000, David Matlack wrote:
> > From: Vipin Sharma <[email protected]>
> > static int vfio_pci_liveupdate_retrieve(struct liveupdate_file_op_args
> > *args)
> > {
> > - return -EOPNOTSUPP;
> > + struct vfio_pci_core_device_ser *ser;
> > + struct vfio_device *device;
> > + struct folio *folio;
> > + struct file *file;
> > + int ret;
> > +
> > + folio = kho_restore_folio(args->serialized_data);
> > + if (!folio)
> > + return -ENOENT;
>
> Should this be consistent with the behavior of pci_flb_retrieve() which panics
> on failure? The short circuit failure paths which follow leak the folio,
> which seems like a hygiene issue, but the practical significance is moot if
> vfio_pci_liveupdate_retrieve() failure is catastrophic anyways?
pci_flb_retrieve() is used during boot. If it fails, we risk DMA
corrupting any memory region, so a panic makes sense. In contrast,
this retrieval happens once we are already in userspace, allowing the
user to decide how to handle the failure to recover the preserved
cdev.
Pasha
>
> > +
> > + ser = folio_address(folio);
> > +
> > + device = vfio_find_device(ser, match_device);
> > + if (!device)
> > + return -ENODEV;
> > +
> > + /*
> > + * During a Live Update userspace retrieves preserved VFIO cdev files
> > by
> > + * issuing an ioctl on /dev/liveupdate rather than by opening VFIO
> > + * character devices.
> > + *
> > + * To handle that scenario, this routine simulates opening the VFIO
> > + * character device for userspace with an anonymous inode. The
> > returned
> > + * file has the same properties as a cdev file (e.g. operations are
> > + * blocked until BIND_IOMMUFD is called), aside from the inode
> > + * association.
> > + */
> > + file = anon_inode_getfile_fmode("[vfio-device-liveupdate]",
> > + &vfio_device_fops, NULL,
> > + O_RDWR, FMODE_PREAD | FMODE_PWRITE);
> > +
> > + if (IS_ERR(file)) {
> > + ret = PTR_ERR(file);
> > + goto out;
> > + }
> > +
> > + ret = __vfio_device_fops_cdev_open(device, file);
> > + if (ret) {
> > + fput(file);
> > + goto out;
> > + }
> > +
> > + args->file = file;
> > +
> > +out:
> > + /* Drop the reference from vfio_find_device() */
> > + put_device(&device->device);
> > +
> > + return ret;
> > +}
