On Thu, May 16, 2013 at 12:27:52PM +0100, Nicholas Thomas wrote: > On Thu, 2013-05-16 at 11:40 +0300, Michael S. Tsirkin wrote: > > On Thu, May 16, 2013 at 09:20:55AM +0100, Nicholas Thomas wrote: > > > Hi, > > > > > > On Thu, 2013-05-16 at 09:27 +0300, Michael S. Tsirkin wrote: > > > > On Thu, May 16, 2013 at 09:24:05AM +0300, Michael S. Tsirkin wrote: > > > > > Is this with or without vhost-net in host? > > > > > > > > never mind, I see it's without. > > > > Try to enable vhost-net (you'll have to switch to -netdev syntax > > > > for that to work) and see if this help. > > > > If it does it's likely a qemu bug if not probably a guest bug. > > > > > > Switching to -netdev is non-trivial for me, unfortunately. > > > > Interesting. Why is that? > > Our setup is bond0 <-> vlanX <-> bridgeX <-> [ tap devices ] and we do > all that outside of qemu at the moment, specifying -net tap,ifname=... - > we also run some processes on the TAP interface and insert a bunch of > ebtables rules between creating it and starting qemu. Duplicating that > with -net bridge seemed close to impossible, and -netdev tap was > throwing EBUSY from /dev/net/tun. I guess our external magic should be > using ,fd= instead.
I'm not sure what's wrong with -netdev tap. You don't have to use fd=, you can specify ifname= with netdev as well. Here's what I use: -net nic,model=virtio,netdev=foo -netdev tap,id=foo,ifname=msttap0,script=/home/mst/ifup,downscript=no,vhost=on the netdev/id pair above is almost the same as vlan=20 in your example, except there's always exactly one frontend and one backend in the netdev case, vlans let you connect more than 2 devices. > > > Anyway, it's > > > definitely a qemu bug - it happens on kernels 3.2 and 3.9 with 1.4.1, > > > but doesn't happen with qemu 0.15.0 or 1.5.0rc1. > > > > > > I'll have a dig through git to see if I can identify the patch that > > > resolves it. It feels-like qemu sometimes stops reading from the tap > > > file descriptor between ipxe exiting and the linux kernel bringing up > > > the network interface, and never recovers from that. > > > > > > /Nick > > > > You can try to bisect, yes. > > Work have decided to accept 1.5.0 when it arrives instead, so I'm afraid > I won't be working on this after all. > > /Nick > >
