[Qemu-devel] vhost-net issue with multiples interfaces using MQ

[William Dauchy <william@gandi.net>]

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Hello,

Using qemu2.1.0, a linux v3.14.X x86_64 as host and a linux v3.12.X x86_64 as guest
I'm starting a VM with these network interfaces:

[netdev "vifA.0"]
  type = "tap"
  vhost = "on"
  ifname = "vifA.0"
  downscript = "no"
  script = "no"
  queues = "2"

[device "vifA.0"]
  driver = "virtio-net-pci"
  netdev = "vifA.0"
  mac = "00:16:3e:1a:4e:11"
  mq = "on"
  vectors = "5"

(and same config for two other interfaces but with a different MAC address)

In the error message I'm getting during startup:
unable to start vhost net: 95: falling back on userspace virtio

I saw that it's failing in `vhost_dev_start` where `vhost_dev_set_features` is returning an error.
r = vhost_dev_set_features(hdev, hdev->log_enabled);
I'm hitting the issue starting from three interfaces, i.e no problem with one or two.
I also don't have the issue with disabling multi queue.

Am I wrong on something? What can I do to help debug this situation?

Regards,
-- 
William

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