[Qemu-devel] [RFC 0/5] vfio: Introduce Live migration capability to vfio_mdev device

[Yulei Zhang]

Summary

This series RFC would like to introduce the live migration capability
to vfio_mdev device. 

As currently vfio_mdev device don't support migration, we introduce a
device flag VFIO_DEVICE_FLAGS_MIGRATABLE to help determine whether the
mdev device can be migrate or not, it will check the flag during the 
device initialization and decide to init the new vfio region 
VFIO_PCI_DEVICE_STATE_REGION_INDEX. 

The intention to add the new region is using it for vfio_mdev device
status save and restore during the migration. The access to this region
will be trapped and forward to the vfio_mdev device driver. There is 
an alternative way to achieve it is to add a new vfio ioctl to help fetch
and save the device status.

Also this series include two new vfio ioctl 
#define VFIO_DEVICE_PCI_STATUS_SET      _IO(VFIO_TYPE, VFIO_BASE + 14)
#define VFIO_DEVICE_PCI_GET_DIRTY_BITMAP _IO(VFIO_TYPE, VFIO_BASE + 15)

The first one is used to contorl the device running status, we want to
stop the mdev device before quary the status from its device driver and
restart the device after migration.
The second one is used to do the mdev device dirty page synchronization.

So the vfio_mdev device migration sequence would be
Source VM side:
                        start migration
                                |
                                V
                 get the cpu state change callback
                use status set ioctl to stop the mdev device
                                |
                                V
                 save the deivce status into Qemufile which is 
                 read from the new vfio device status region
                                |
                                V
                   quary the dirty page bitmap from deivce
                    and add into qemu dirty list for sync

Target VM side:
                   restore the mdev device after get the
                     saved status context from Qemufile
                                |
                                V
                     get the cpu state change callback
                     use status set ioctl to start the mdev 
                     device to put it in running status
                                |
                                V
                        finish migration

Yulei Zhang (5):
  vfio: introduce a new VFIO region for migration support
  vfio: Add struct vfio_vmstate_info to introduce vfio device put/get
    funtion
  vfio: introduce new VFIO ioctl VFIO_DEVICE_PCI_STATUS_SET
  vfio: use vfio_device_put/vfio_device_get for device status
    save/restore
  vifo: introduce new VFIO ioctl VFIO_DEVICE_PCI_GET_DIRTY_BITMAP

 hw/vfio/pci.c              | 204 ++++++++++++++++++++++++++++++++++++++++++++-
 hw/vfio/pci.h              |   3 +
 linux-headers/linux/vfio.h |  34 +++++++-
 3 files changed, 239 insertions(+), 2 deletions(-)

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2.7.4