These patches add possibility to pass VFIO device to QEMU using file
descriptors of VFIO container/group, instead of creating those by QEMU.
This allows to take away permissions to open /dev/vfio/* from QEMU and
delegate that to managment layer like libvirt.
The VFIO API doen't allow to pass just fd of device, since we also need to have
VFIO container and group. So these patches allow to pass created VFIO
container/group
to QEMU via command line/QMP, e.g. like this:
-object vfio-container,id=ct,fd=5 \
-object vfio-group,id=grp,fd=6,container=ct \
-device vfio-pci,host=05:00.0,group=grp
A bit more detailed example can be found in the test:
tests/avocado/vfio.py
*Possible future steps*
Also these patches could be a step for making local migration (within one host)
of the QEMU with VFIO devices.
I've built some prototype on top of these patches to try such idea.
In short the scheme of such migration is following:
- migrate source VM to file.
- retrieve fd numbers of VFIO container/group/device via new property and
qom-get command
- get the actual file descriptor via SCM_RIGHTS using new qmp command
'returnfd' which
sends fd from QEMU by the number: { 'command': 'returnfd', 'data': {'fd':
'int'}}
- shutdown source VM
- launch destination VM, plug VFIO devices using obtained file descriptors.
- PCI device reset duriing plugging the device avoided with the help of new
parameter
on vfio-pci device.
This is alternative to 'cpr-exec' migration scheme proposed here:
https://lore.kernel.org/qemu-devel/1658851843-236870-1-git-send-email-steven.sist...@oracle.com/
Unlike cpr-exec it doesn't require new kernel flags
VFIO_DMA_UNMAP_FLAG_VADDR/VFIO_DMA_MAP_FLAG_VADDR
And doesn't require new migration mode, just some additional steps from
management layer.
Andrey Ryabinin (4):
vfio: add vfio-container user createable object
vfio: add vfio-group user createable object
vfio: Add 'group' property to 'vfio-pci' device
tests/avocado/vfio: add test for vfio devices
hw/vfio/ap.c | 2 +-
hw/vfio/ccw.c | 2 +-
hw/vfio/common.c | 471 +++++++++++++++++++++++-----------
hw/vfio/pci.c | 10 +-
hw/vfio/platform.c | 2 +-
hw/vfio/trace-events | 4 +-
include/hw/vfio/vfio-common.h | 10 +-
qapi/qom.json | 29 +++
tests/avocado/vfio.py | 156 +++++++++++
9 files changed, 525 insertions(+), 161 deletions(-)
create mode 100644 tests/avocado/vfio.py
--
2.37.3
