Re: [Qemu-devel] [PATCH v6 01/13] block: Add op blocker type "device IO"

[Paolo Bonzini]

On 28/05/2015 13:11, Fam Zheng wrote:
> > Whoever uses ioeventfd needs to implement pause/resume, yes---not just
> > dataplane, also "regular" virtio-blk/virtio-scsi.
> > 
> > However, everyone else should be okay, because the bottom half runs
> > immediately and the big QEMU lock is not released in the meanwhile.  So
> > the CPUs have no occasion to run.  This needs a comment!
> 
> I'm not sure. It seems timer callbacks also do I/O, for example
> nvme_process_sq().

Right, that's also true for USB devices. :(

Perhaps we can skip block_job_defer_to_main_loop if not necessary
(bs->aio_context == qemu_get_aio_context()).

Paolo