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From 335e94e588ded0f1163ef20c72d78fcf725b1236 Mon Sep 17 00:00:00 2001
From: Julia Suvorova <>
Date: Tue, 4 Feb 2020 18:20:04 +0000
Subject: [PATCH 3/6] clean up callback when del virtqueue

RH-Author: Julia Suvorova <>
Message-id: <>
Patchwork-id: 93703
O-Subject: [RHEL-8.2.0 qemu-kvm PATCH 1/4] clean up callback when del virtqueue
Bugzilla: 1708480
RH-Acked-by: Stefan Hajnoczi <>
RH-Acked-by: Cornelia Huck <>
RH-Acked-by: Michael S. Tsirkin <>

From: liujunjie <>

Before, we did not clear callback like handle_output when delete
the virtqueue which may result be segmentfault.
The scene is as follows:
1. Start a vm with multiqueue vhost-net,
2. then we write VIRTIO_PCI_GUEST_FEATURES in PCI configuration to
triger multiqueue disable in this vm which will delete the virtqueue.
In this step, the tx_bh is deleted but the callback virtio_net_handle_tx_bh
still exist.
3. Finally, we write VIRTIO_PCI_QUEUE_NOTIFY in PCI configuration to
notify the deleted virtqueue. In this way, virtio_net_handle_tx_bh
will be called and qemu will be crashed.

Although the way described above is uncommon, we had better reinforce it.

Signed-off-by: liujunjie <>
Signed-off-by: Jason Wang <>
(cherry picked from commit 7da2d99fb9fbf30104125c061caaff330e362d74)
Signed-off-by: Danilo C. L. de Paula <>
 hw/virtio/virtio.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index fce199e..6356bf3 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1609,6 +1609,8 @@ void virtio_del_queue(VirtIODevice *vdev, int n)
     vdev->vq[n].vring.num = 0;
     vdev->vq[n].vring.num_default = 0;
+    vdev->vq[n].handle_output = NULL;
+    vdev->vq[n].handle_aio_output = NULL;
 static void virtio_set_isr(VirtIODevice *vdev, int value)