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From eb2b3b18edc3af42f52ca5b3f30aa8bfbd08206a Mon Sep 17 00:00:00 2001
From: Maxime Coquelin <maxime.coquelin@redhat.com>
Date: Wed, 13 Dec 2017 09:51:09 +0100
Subject: [PATCH 4/6] vhost: destroy unused virtqueues when multiqueue not
negotiated
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>
(cherry picked from commit e29109323595beb3884da58126ebb3b878cb66f5)
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
dpdk-17.11/lib/librte_vhost/vhost_user.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/dpdk-17.11/lib/librte_vhost/vhost_user.c b/dpdk-17.11/lib/librte_vhost/vhost_user.c
index 471b1612c..1848c8de9 100644
--- a/dpdk-17.11/lib/librte_vhost/vhost_user.c
+++ b/dpdk-17.11/lib/librte_vhost/vhost_user.c
@@ -216,6 +216,25 @@ 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;
}
--
2.14.3