Add a Snapshot and Restore section to docs/vfio.md covering the
migration v2 requirements (Linux 5.18 kernel, variant VFIO
driver such as mlx5_vfio_pci) and the restore sequence for
devices that advertise migration v2.
The behavior description covers the full restore sequence. It
documents the RUNNING to RESUMING single transition (the kernel
walks the intermediate STOP arc), the post load PCI_COMMAND push
to the device, and the MSI or MSI-X eventfd rearm that the
kernel state does not carry. Behavior matches QEMU
vfio_pci_load_config().
It notes one limitation, the snapshot format stores the opaque
device blob as base64 inside the snapshot JSON, which may benefit
from a binary transport path for very large state.
docs/snapshot_restore.md replaces its VFIO out of scope
limitation with a short section that points to docs/vfio.md for
the requirements and behavior.
Signed-off-by: Saravanan D <saravanand@crusoe.ai>
f5967cf287