Re: [Xen-devel] [PATCH] xen-bus/block: explicitly assign event channels to an AioContext

[Julien Grall <jgrall@xxxxxxxxxx>]

Hi Anthony,

On 19/12/2019 17:11, Anthony PERARD wrote:
> On Mon, Dec 16, 2019 at 02:34:51PM +0000, Paul Durrant wrote:
> > It is not safe to close an event channel from the QEMU main thread when
> > that channel's poller is running in IOThread context.
> >
> > This patch adds a new xen_device_set_event_channel_context() function
> > to explicitly assign the channel AioContext, and modifies
> > xen_device_bind_event_channel() to initially assign the channel's poller
> > to the QEMU main thread context. The code in xen-block's dataplane is
> > then modified to assign the channel to IOThread context during
> > xen_block_dataplane_start() and de-assign it during in
> > xen_block_dataplane_stop(), such that the channel is always assigned
> > back to main thread context before it is closed. aio_set_fd_handler()
> > already deals with all the necessary synchronization when moving an fd
> > between AioContext-s so no extra code is needed to manage this.
> >
> > Reported-by: Julien Grall <jgrall@xxxxxxxxxx>
> > Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
> Reviewed-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
I can't find the patch in QEMU upstream. Are we missing any ack/review 
for this patch?
> > Tested against an HVM debian guest with a QCOW2 image as system disk, and
> > as a hot-plugged/unplgged secondary disk.
> And I've run an osstest flight with the patch.
>
> Thanks,
Cheers,

--
Julien Grall

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