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From eb2b3b18edc3af42f52ca5b3f30aa8bfbd08206a Mon Sep 17 00:00:00 2001
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From: Maxime Coquelin <maxime.coquelin@redhat.com>
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Date: Wed, 13 Dec 2017 09:51:09 +0100
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Subject: [PATCH 4/6] vhost: destroy unused virtqueues when multiqueue not
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negotiated
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QEMU sends VHOST_USER_SET_VRING_CALL requests for all queues
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declared in QEMU command line before the guest is started.
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It has the effect in DPDK vhost-user backend to allocate vrings
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for all queues declared by QEMU.
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If the first driver being used does not support multiqueue,
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the device never changes to VIRTIO_DEV_RUNNING state as only
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the first queue pair is initialized. One driver impacted by
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this bug is virtio-net's iPXE driver which does not support
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VIRTIO_NET_F_MQ feature.
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It is safe to destroy unused virtqueues in SET_FEATURES request
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handler, as it is ensured the device is not in running state
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at this stage, so virtqueues aren't being processed.
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Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
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Acked-by: Laszlo Ersek <lersek@redhat.com>
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Acked-by: Yuanhan Liu <yliu@fridaylinux.org>
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(cherry picked from commit e29109323595beb3884da58126ebb3b878cb66f5)
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Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
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---
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dpdk-17.11/lib/librte_vhost/vhost_user.c | 19 +++++++++++++++++++
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1 file changed, 19 insertions(+)
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diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
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index 471b1612c..1848c8de9 100644
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--- a/lib/librte_vhost/vhost_user.c
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+++ b/lib/librte_vhost/vhost_user.c
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@@ -216,6 +216,25 @@ vhost_user_set_features(struct virtio_net *dev, uint64_t features)
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(dev->features & (1 << VIRTIO_NET_F_MRG_RXBUF)) ? "on" : "off",
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(dev->features & (1ULL << VIRTIO_F_VERSION_1)) ? "on" : "off");
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+ if (!(dev->features & (1ULL << VIRTIO_NET_F_MQ))) {
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+ /*
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+ * Remove all but first queue pair if MQ hasn't been
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+ * negotiated. This is safe because the device is not
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+ * running at this stage.
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+ */
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+ while (dev->nr_vring > 2) {
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+ struct vhost_virtqueue *vq;
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+
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+ vq = dev->virtqueue[--dev->nr_vring];
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+ if (!vq)
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+ continue;
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+
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+ dev->virtqueue[dev->nr_vring] = NULL;
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+ cleanup_vq(vq, 1);
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+ free_vq(vq);
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+ }
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+ }
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+
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return 0;
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}
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--
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2.14.3
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