Re: [Qemu-devel] [PATCH v9 06/10] replay: fix save/load vm for non-empty queue

[Paolo Bonzini]

On 04/05/2017 15:02, Pavel Dovgalyuk wrote:
>> Understood.  And what checkpoint will you be waiting for during drain,
>> causing a deadlock?
> Every checkpoint processes the queue, but none of them are invoked,
> because iothread (which invokes all the checkpoints) is waiting for the end 
> of the drain.
> 
> And we cannot add a checkpoint into the drain, because then vmstop will
> affect the behavior of the guest.

But it does affect the behavior already when RR is off.  And it
shouldn't be a problem if it does in record mode (as long as the effect
can be replayed).

If RR cannot do drain reliably, not even in record mode, that is a huge
problem because a lot of block layer operations assume they can.

Paolo