From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: vhost, something changed between 2.6.35 and 2.6.36 ?
Date: Sun, 12 Sep 2010 14:05:15 +0200
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To: Dhaval Giani <dhaval.lists@thegianis.in>
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On Fri, Sep 10, 2010 at 03:37:36PM +0200, Dhaval Giani wrote:
> Hi,
> 
> I have been trying to get vhost+macvtap to work for me. I run it as
> 
> /root/qemu-kvm-vhost-net/bin/qemu-system-x86_64 -hda $IMAGE  -serial
> stdio -monitor telnet::4444,server,nowait -vnc :4: -m 3G -net
> nic,model=virtio,macaddr=$MACADDR,netdev=macvtap0 -netdev
> tap,id=macvtap0,vhost=on,fd=3 3<> /dev/tap5
> 
> in 2.6.35, which worked just fine. On the other hand, with 2.6.36, i
> don't have working networking. I am using the same image and same
> macaddress. The qemu is the version from
> git://git.kernel.org/pub/scm/linux/kernel/git/mst/qemu-kvm.git vhost .

BTW, by now, all these patches are merged so upstream qemu-kvm should work
just fine for you as well.

> Any suggestions will be welcome!
> 
> Thanks,
> Dhaval

You are running this as non-root user, correct?
This could be the permission issue that got fixed
by 87d6a412bd1ed82c14cabd4b408003b23bbd2880.
Could you please check the latest master from Linus,
and let me and the list know? Thanks!

Another thing to try if this does *not* help:

enable CONFIG_DYNAMIC_DEBUG in kernel,
rebuild the kernel,
mount debugfs:

	mount -t debugfs none /sys/kernel/debug

and then enable debug for vhost_net as described in
Documentation/dynamic-debug-howto.txt:

	echo 'module vhost_net +p' > /sys/kernel/debug/dynamic_debug/control

Then start qemu, and after running a test, run dmesg and see if there
are any messages from vhost_net. If yes please send them to
me and to the list.

Thanks!

-- 
MST