Re: [Qemu-devel] [RESEND PATCH] virtio: allow broken device to notify guest

[Stefan Hajnoczi <stefanha@gmail.com>]

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On Wed, May 17, 2017 at 10:17:51AM +0200, Greg Kurz wrote:
> According to section 2.1.2 of the virtio-1 specification:
> 
> "The device SHOULD set DEVICE_NEEDS_RESET when it enters an error state that
> a reset is needed. If DRIVER_OK is set, after it sets DEVICE_NEEDS_RESET,
> the device MUST send a device configuration change notification to the
> driver."
> 
> Commit "f5ed36635d8f virtio: stop virtqueue processing if device is broken"
> introduced a virtio_error() call that just does that:
> 
> - internally mark the device as broken
> - set the DEVICE_NEEDS_RESET bit in the status
> - send a configuration change notification
> 
> Unfortunately, virtio_notify_vector(), called by virtio_notify_config(),
> returns right away when the device is marked as broken and the notification
> isn't sent in this case.
> 
> The spec doesn't say whether a broken device can send notifications
> in other situations or not. But since the driver isn't supposed to do
> anything but to reset the device, it makes sense to keep the check in
> virtio_notify_config().
> 
> Marking the device as broken AFTER the configuration change notification was
> sent is enough to fix the issue.
> 
> Signed-off-by: Greg Kurz <groug@kaod.org>
> Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> ---
>  hw/virtio/virtio.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> Re-sending this patch with Cornelia's Reviewed-by and Cc'ing qemu-stable
> since this is a spec violation, as suggested in:
> 
> Message-ID: <20170427183237-mutt-send-email-mst@kernel.org>
> 
> Cheers,
> 
> --
> Greg

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

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