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

From: Greg Kurz
Subject: [Qemu-devel] [PATCH] virtio: allow broken device to notify guest
Date: Wed, 26 Apr 2017 14:51:17 +0200
User-agent: StGit/0.17.1-20-gc0b1b-dirty

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

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

Marking the device as broken AFTER the configuration change notification was
sent is enough to fix the issue.

Signed-off-by: Greg Kurz <address@hidden>
 hw/virtio/virtio.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 03592c542a55..890b4d7eb751 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2451,12 +2451,12 @@ void GCC_FMT_ATTR(2, 3) virtio_error(VirtIODevice 
*vdev, const char *fmt, ...)
     error_vreport(fmt, ap);
-    vdev->broken = true;
     if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
         virtio_set_status(vdev, vdev->status | VIRTIO_CONFIG_S_NEEDS_RESET);
+    vdev->broken = true;
 static void virtio_memory_listener_commit(MemoryListener *listener)

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