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vhost: destroy unused virtqueues when multiqueue not negotiated

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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.coquelin@redhat.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Yuanhan Liu <yliu@fridaylinux.org>
This commit is contained in:
Maxime Coquelin 2017-12-13 09:51:09 +01:00 committed by Ferruh Yigit
parent 467fe22df9
commit e291093235
1 changed files with 19 additions and 0 deletions

19
lib/librte_vhost/vhost_user.c

@ -187,6 +187,25 @@ 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;
dev->virtqueue[dev->nr_vring] = NULL;
cleanup_vq(vq, 1);
free_vq(vq);
}
}
return 0;
}