support for live migration about libvfio-user HOT 5 CLOSED

I've done some work for supporting live migration in libmuser, I've over simplified most of the code to make it work. There are many open issues, most importantly understanding how some regisiters in the migration region are supposed to work (more information in the code as FIXME and TODO).

from libvfio-user.

Also, check VFIO live migration in QEMU, it might answer lots of questions regarding how registers are used etc.

from libvfio-user.

I see that in hw/vfio/migration.c, as soon as the device transitions to the stop-and-copy phase (before migration data are actually copied), the device configuration state is stored. IIUC the client is responsible for saving/loading it, so no need to do anything in muser.

from libvfio-user.

I received some clarifications on some question I have (https://marc.info/?l=kvm&m=160502788221980&w=2):

• During the stop-and-copy and stopped state the device should only handle migration-specific operations. Any other operation (e.g. vfio-user request) should be explicitly failed.
• Reading data_offset marks a new iteration, so re-reading pending_bytes and data_size is allowed.
• The pending_bytes register is volatile.
• Reading data_size out of sequence if undefined.
• data_offset and data_size are invariant during an iteration.

from libvfio-user.

Fixed.

from libvfio-user.