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? > >> For the >> rest of the QEMU world we should be using iohandler context. So >> assigning monitor dispatcher bottom half to that context. > > This patch relies on the side-effect that iohandler_ctx is only called > later by the main loop, which seems to prevent the crash below. > > What is the actual crash/problem? You mentioned the GIC, but what does > that have to do with monitor code crashing? > -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
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