Re: [Qemu-devel] [PATCH for-2.12] monitor: bind dispatch bh to iohandler context

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Wed, Apr 04, 2018 at 10:07:34AM -0500, Eric Blake wrote:
> On 04/04/2018 09:22 AM, Stefan Hajnoczi wrote:
> > On Tue, Apr 03, 2018 at 01:01:15PM +0800, Peter Xu wrote:
> >> Eric Auger reported the problem days ago that OOB broke ARM when running
> >> with libvirt:
> >>
> >> http://lists.gnu.org/archive/html/qemu-devel/2018-03/msg06231.html
> >>
> >> This patch fixes the problem.
> >>
> >> It's not really needed now since we have turned OOB off now, but it's
> >> still a bug fix, and it'll start to work when we turn OOB on for ARM.
> >>
> >> The problem was that the monitor dispatcher bottom half was bound to
> >> qemu_aio_context, but that context seems to be for block only.
> > 
> > No, it is not block-only.  iohandler_ctx is for the legacy
> > qemu_set_fd_handler() API only and modern code should use
> > qemu_aio_context.
> > 
> > The difference between qemu_aio_context and iohandler_ctx is that
> > aio_poll(qemu_aio_context) does not process iohandler_ctx (since it's a
> > difference context).  That is the legacy behavior that
> > qemu_set_fd_handler() expects and it's implemented by keeping a separate
> > iohandler_ctx.
> 
> Do I need to put a hold on my pull request while we come to a better
> understanding of root cause, or is this patch still okay to include?

The cover letter says this patch is not critical for 2.12:

"It's not really needed now since we have turned OOB off now, but it's
still a bug fix, and it'll start to work when we turn OOB on for ARM."

Please hold off until the nature of the bug is understood.

Thanks,
Stefan

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