Re: [Qemu-devel] [PATCH 00/13] virtio migration: Flip outer layer to vmstate

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jun 21, 2016 at 08:13:54PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Hi,
>   This series converts the outer most layer of virtio to
> use VMState macros;  this is the easy bit, but I'm hoping that
> having done that, the next trick is to nibble away at the virtio_save/load
> functions and all of the zillions of device/bus helpers.
> 
> I think the first two patches are the most controversial;
> they remove migration support for old version of virtio-net and virtio-serial;
> (for virtio-net versions prior to 0.11 and for virtio-serial prior to 0.13).
> I'm working on the basis that migration has bit rotted enough so
> that the streams aren't migration compatible for that long back
> on upstream - but if anyone knows otherwise please shout.

I'm ok with removing 0.11 migration compat code.
But doesn't the serial change break 0.12 as well?

> The reason for doing those is that the virtio structure makes
> it a bit tricky to pass the outer device version number down
> through VMState to the device specific code (I can do it
> as a hack if necessary using a dummy is_needed function);
> and with -net and -serial compatibility sorted I think
> every other device just supports a single version.
> 
> My main reason for doing this is to get rid of the
> calls to register_savevm ('going to disappear as soon..' since 2010)
> 
> It's lightly tested using the magic line:
> ./x86_64-softmmu/qemu-system-x86_64 -nographic -machine pc-i440fx-2.6,accel=kvm -cpu qemu64 -m 2048M -drive file=/home/vmimages/f20.img,if=none,id=drivea -device virtio-scsi,id=scsi -device scsi-hd,drive=drivea -device virtio-rng -device virtio-serial -chardev file,id=test,path=/tmp/testfile -device virtconsole,chardev=test,name=foo -virtfs local,path=/home,security_model=passthrough,mount_tag=host_share  -device virtio-gpu  -drive file=/home/vmimages/jeos-19-64.qcow2,id=jeos,if=none -device virtio-blk,drive=jeos  -device virtio-balloon
> 
> Thoughts?
> 
> Dave
> 
> Dr. David Alan Gilbert (13):
>   virtio-net: Remove old migration version support
>   virtio-serial: Remove old migration version support
>   virtio: Migration helper function and macro
>   virtio-scsi: Wrap in vmstate
>   virtio-blk: Wrap in vmstate
>   virtio-rng: Wrap in vmstate
>   virtio-balloon: Wrap in vmstate
>   virtio-net: Wrap in vmstate
>   virtio-serial: Wrap in vmstate
>   9pfs: Wrap in vmstate
>   virtio-input: Wrap in vmstate
>   virtio-gpu: Wrap in vmstate
>   virtio: Update migration docs
> 
>  docs/virtio-migration.txt   |   6 ++-
>  hw/9pfs/virtio-9p-device.c  |  14 +++---
>  hw/block/virtio-blk.c       |  16 +++----
>  hw/char/virtio-serial-bus.c |  62 +++++++++------------------
>  hw/display/virtio-gpu.c     |  17 +++-----
>  hw/input/virtio-input.c     |  26 +++--------
>  hw/net/virtio-net.c         | 102 +++++++++++++++++---------------------------
>  hw/scsi/virtio-scsi.c       |  21 +++------
>  hw/virtio/virtio-balloon.c  |  19 +++------
>  hw/virtio/virtio-rng.c      |  20 +++------
>  hw/virtio/virtio.c          |   6 +++
>  include/hw/virtio/virtio.h  |  20 +++++++++
>  12 files changed, 130 insertions(+), 199 deletions(-)
> 
> -- 
> 2.7.4