[Qemu-devel] [RFC V2 0/4] 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 new vfio subtype region VFIO_REGION_SUBTYPE_INTEL_IGD_DEVICE_STATE
for Intel vGPU device, during the vfio device initialization, the mdev
device will be set to migratable if the new region exist.  

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. And we use 
the first byte in the new region to control the running state of mdev
device.

Meanwhile we add one new ioctl VFIO_IOMMU_GET_DIRTY_BITMAP to help 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, write to the
                 subregion's first byte to stop the mdev device
                                |
                                V
                 quary the dirty page bitmap from iommu container 
                 and add into qemu dirty list for synchronization
                                |
                                V
                 save the deivce status into Qemufile which is 
                     read from the vfio device subregion

Target VM side:
                   restore the mdev device after get the
                     saved status context from Qemufile
                                |
                                V
                     get the cpu state change callback
                     write to subregion's first byte to 
                      start the mdev device to put it in 
                      running status
                                |
                                V
                        finish migration

V1->V2:
Per Alex's suggestion:
1. use device subtype region instead of VFIO PCI fixed region.
2. remove unnecessary ioctl, use the first byte of subregion to 
   control the running state of mdev device.  
3. for dirty page synchronization, implement the interface with
   VFIOContainer instead of vfio pci device.

Yulei Zhang (4):
  vfio: introduce a new VFIO sub region for mdev device migration
    support
  vfio: Add vm status change callback to stop/restart the mdev device
  vfio: Add struct vfio_vmstate_info to introduce put/get callback
    funtion     for vfio device status save/restore
  vifo: introduce new VFIO ioctl VFIO_IOMMU_GET_DIRTY_BITMAP

 hw/vfio/common.c              |  32 +++++++++
 hw/vfio/pci.c                 | 164 +++++++++++++++++++++++++++++++++++++++++-
 hw/vfio/pci.h                 |   1 +
 include/hw/vfio/vfio-common.h |   1 +
 linux-headers/linux/vfio.h    |  26 ++++++-
 5 files changed, 220 insertions(+), 4 deletions(-)

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2.7.4