Re: [Qemu-devel] [PATCH 7/9] virtio-blk: live migrate s->rq with multiqueue

[Stefan Hajnoczi]

On Sat, May 21, 2016 at 05:37:27PM +0200, Paolo Bonzini wrote:
> 
> 
> On 21/05/2016 01:40, Stefan Hajnoczi wrote:
> >      while (req) {
> >          qemu_put_sbyte(f, 1);
> 
> Could you just put an extra 32-bit queue id here if num_queues > 1?  A
> guest with num_queues > 1 cannot be started on pre-2.7 QEMU, so you can
> change the migration format (if virtio were using vmstate, it would be a
> VMSTATE_UINT32_TEST).

That's a good point: the same command-line would not work on old QEMU so
there is no possibility of new->old migration in the first place!

Your solution is much simpler than my hack (which took me a long time to
find and I was kind of proud of).  Will change for v2.

Stefan

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