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From: Stefan Hajnoczi <stefanha@redhat.com>
To: kvm@vger.kernel.org
Cc: mst@redhat.com, virtualization@lists.linux-foundation.org,
	jelledejong@powercraft.nl, Ben Hutchings <ben@decadent.org.uk>,
	David Miller <davem@davemloft.net>
Subject: TUN_F_UFO change breaks live migration
Date: Tue, 11 Nov 2014 10:58:49 +0000	[thread overview]
Message-ID: <20141111105849.GA8482@stefanha-thinkpad.redhat.com> (raw)


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Commit 3d0ad09412ffe00c9afa201d01effdb6023d09b4 ("drivers/net: Disable
UFO through virtio") breaks live migration of KVM guests from older to
newer host kernels:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=3d0ad09412ffe00c9afa201d01effdb6023d09b4

The problem occurs when a guest running on a host kernel without commit
3d0ad0941 in tun.ko attempts to live migration to a host with commit
3d0ad0941.

Live migration fails in QEMU with the following error message:

  virtio-net: saved image requires TUN_F_UFO support

The old host tun.ko advertised support for TUN_F_UFO.  The new host
tun.ko does not and that's why QEMU aborts live migration.  QEMU cannot
change the features of a running virtio-net device.

tuxcrafter provided logs from two Debian hosts migrating from
3.2.60-1+deb7u3 to 3.2.63-2+deb7u1:

http://paste.debian.net/131264/

I haven't investigated enough to suggest a fix, just wanted to bring it
to your attention.  Soon a lot of people will be hitting this problem as
they upgrade their infrastructure and migrate guests - seems like a
critical issue.

Stefan

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             reply	other threads:[~2014-11-11 10:58 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-11-11 10:58 Stefan Hajnoczi [this message]
2014-11-11 12:17 ` TUN_F_UFO change breaks live migration Ben Hutchings
     [not found] ` <1415708246.3398.88.camel@decadent.org.uk>
2014-11-11 15:57   ` Michael S. Tsirkin
2014-11-11 16:38     ` David Miller
2014-11-11 17:07     ` Ben Hutchings
2014-11-11 17:12     ` [PATCH net] Revert "drivers/net: Disable UFO through virtio" in macvtap and tun Ben Hutchings
2014-11-11 21:33       ` David Miller
2014-11-12 19:02       ` Stefan Hajnoczi
2014-11-13 12:00         ` Jelle de Jong
2014-12-01  9:43       ` Michael S. Tsirkin
2014-12-02 17:44       ` Vlad Yasevich

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