QEMU sends VHOST_USER_SET_VRING_CALL requests for all queues
declared in QEMU command line before the guest is started.
It has the effect in DPDK vhost-user backend to allocate vrings
for all queues declared by QEMU.
If the first driver being used does not support multiqueue,
the device never changes to VIRTIO_DEV_RUNNING state as only
the first queue pair is initialized. One driver impacted by
this bug is virtio-net's iPXE driver which does not support
VIRTIO_NET_F_MQ feature.
It is safe to destroy unused virtqueues in SET_FEATURES request
handler, as it is ensured the device is not in running state
at this stage, so virtqueues aren't being processed.
Signed-off-by: Maxime Coquelin <maxime.coque...@redhat.com>
---
lib/librte_vhost/vhost_user.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index a5e1f2482..92a219052 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -216,6 +216,24 @@ vhost_user_set_features(struct virtio_net *dev, uint64_t
features)
(dev->features & (1 << VIRTIO_NET_F_MRG_RXBUF)) ? "on" : "off",
(dev->features & (1ULL << VIRTIO_F_VERSION_1)) ? "on" : "off");
+ if (!(dev->features & (1ULL << VIRTIO_NET_F_MQ))) {
+ /*
+ * Remove all but first queue pair if MQ hasn't been
+ * negotiated. This is safe because the device is not
+ * running at this stage.
+ */
+ while (dev->nr_vring > 2) {
+ struct vhost_virtqueue *vq;
+
+ vq = dev->virtqueue[--dev->nr_vring];
+ if (!vq)
+ continue;
+
+ cleanup_vq(vq, 1);
+ free_vq(vq);
+ }
+ }
+
return 0;
}
--
2.14.3
