Re: [Qemu-devel] [PATCH] virtio: always use handle_aio_output if registered

[Stefan Hajnoczi <stefanha@gmail.com>]

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On Tue, Feb 28, 2017 at 02:21:32PM +0100, Paolo Bonzini wrote:
> Commit ad07cd6 ("virtio-scsi: always use dataplane path if ioeventfd is
> active", 2016-10-30) and 9ffe337 ("virtio-blk: always use dataplane
> path if ioeventfd is active", 2016-10-30) broke the virtio 1.0
> indirect access registers.
> 
> The indirect access registers bypass the ioeventfd, so that virtio-blk
> and virtio-scsi now repeatedly try to initialize dataplane instead of
> triggering the guest->host EventNotifier.  Detect the situation by
> checking vq->handle_aio_output; if it is not NULL, trigger the
> EventNotifier, which is how the device expects to get notifications
> and in fact the only thread-safe manner to deliver them.
> 
> Fixes: ad07cd6
> Fixes: 9ffe337
> Cc: qemu-stable@nongnu.org
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  hw/virtio/virtio.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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