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Date: Tue, 15 Mar 2016 09:50:40 -0000
From: Liang Chen <liang.chen@canonical.com>
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Subject: [Qemu-devel] [Bug 1546445] Re: support vhost user without
	specifying vhostforce
Reply-To: Bug 1546445 <1546445@bugs.launchpad.net>
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To: qemu-devel@nongnu.org

** Tags added: sts sts-sru

-- =

You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1546445

Title:
  support vhost user without specifying vhostforce

Status in Ubuntu Cloud Archive:
  In Progress
Status in QEMU:
  Fix Released
Status in qemu package in Ubuntu:
  Fix Released
Status in qemu source package in Vivid:
  Won't Fix
Status in qemu source package in Wily:
  Fix Released

Bug description:
  [Impact]

   * vhost-user falls back to virtio-net which causes performance lose
  without specifying the vhostforce option. But it should be the default
  behavior for vhost-user, since guests using PMD doesn't support msi-x.

  [Test Case]

    create a vhost-user virtio backend without specifying the vhostforce op=
tion, i.e. -netdev type=3Dvhost-user,id=3Dmynet1,chardev=3D<char_dev_for_th=
e_controll_channel>
    start the VM
    vhost-user is not enabled

  [Regression Potential]

   * none

  vhost user nic doesn't support non msi guests(like pxe stage) by default.
  Vhost user nic can't fall back to qemu like normal vhost net nic does. So=
 we should
  enable it for non msi guests.

  The problem has been fix in qemu upstream  -
  http://git.qemu.org/?p=3Dqemu.git;a=3Dcommitdiff;h=3D24f938a682d934b13386=
3eb421aac33592f7a09e.
  And the patch needs to be backported to 1:2.2+dfsg-5expubuntu9.8 .

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