docs: kvm: vfio: Suggest KVM_DEV_VFIO_GROUP_ADD vs VFIO_GROUP_GET_DEVICE_FD ordering

as some vfio_device's open_device op requires kvm pointer and kvm pointer
set is part of GROUP_ADD.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20230421053611.55839-1-yi.l.liu@intel.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Yi Liu 2023-04-20 22:36:11 -07:00 committed by Alex Williamson
parent 38e4614c27
commit 705b004ee3

View File

@ -39,3 +39,8 @@ KVM_DEV_VFIO_GROUP attributes:
- @groupfd is a file descriptor for a VFIO group;
- @tablefd is a file descriptor for a TCE table allocated via
KVM_CREATE_SPAPR_TCE.
The GROUP_ADD operation above should be invoked prior to accessing the
device file descriptor via VFIO_GROUP_GET_DEVICE_FD in order to support
drivers which require a kvm pointer to be set in their .open_device()
callback.