1 files changed, 21 insertions, 0 deletions
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index e680720ddddc..4c3d548e9c96 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -717,6 +717,9 @@ enum {
  *	  affected devices are represented in the dev_set and also owned by
  *	  the user.  This flag is available only when
  *	  flag VFIO_PCI_HOT_RESET_FLAG_DEV_ID is set, otherwise reserved.
+ *	  When set, user could invoke VFIO_DEVICE_PCI_HOT_RESET with a zero
+ *	  length fd array on the calling device as the ownership is validated
+ *	  by iommufd_ctx.
  *
  * Return: 0 on success, -errno on failure:
  *	-enospc = insufficient buffer, -enodev = unsupported for device.
@@ -748,6 +751,24 @@ struct vfio_pci_hot_reset_info {
  * VFIO_DEVICE_PCI_HOT_RESET - _IOW(VFIO_TYPE, VFIO_BASE + 13,
  *				    struct vfio_pci_hot_reset)
  *
+ * A PCI hot reset results in either a bus or slot reset which may affect
+ * other devices sharing the bus/slot.  The calling user must have
+ * ownership of the full set of affected devices as determined by the
+ * VFIO_DEVICE_GET_PCI_HOT_RESET_INFO ioctl.
+ *
+ * When called on a device file descriptor acquired through the vfio
+ * group interface, the user is required to provide proof of ownership
+ * of those affected devices via the group_fds array in struct
+ * vfio_pci_hot_reset.
+ *
+ * When called on a direct cdev opened vfio device, the flags field of
+ * struct vfio_pci_hot_reset_info reports the ownership status of the
+ * affected devices and this ioctl must be called with an empty group_fds
+ * array.  See above INFO ioctl definition for ownership requirements.
+ *
+ * Mixed usage of legacy groups and cdevs across the set of affected
+ * devices is not supported.
+ *
  * Return: 0 on success, -errno on failure.
  */
 struct vfio_pci_hot_reset {