Thank you Stefan! I figured it out and it now works. I read on your blog that one can pass QEMU commands on libvirt (http://blog.vmsplice.net/2011/04/how-to-pass-qemu-command-line-options.html). Would it be possible to fully define a network interface through this and there completely avoiding the libvirt commands for network interfaces? Thank you. On Mon, Feb 27, 2017 at 2:04 AM, Stefan Hajnoczi <stefanha@xxxxxxxxx> wrote: > On Fri, Feb 24, 2017 at 08:37:51AM -0800, Roberto Cardona wrote: >> I'm trying to start a virtual machine by calling qemu-kvm directly but >> I am having issues with the vhost file descriptor (vhostfd). >> >> According to qemu's source code you must pass the file descriptor of >> the previously opened vhost_net device so, in order to do this, I am >> using a python script with something like this: os.open( >> "/dev/vhost-net", os.O_RDWR). Afterwards it passes this to qemu-kvm as >> a subprocess. >> >> I took this off the command that libvirt generates so I know this work >> and all kernel modules are enabled. >> >> Is there any workaround for this so that I can call qemu-kvm directly >> without libvirt? >> >> Error messages: >> qemu-kvm: -netdev tap,id=hostnet0,vhost=on,fd=3: TUNGETIFF ioctl() >> failed: Inappropriate ioctl for device >> qemu-kvm: -netdev tap,id=hostnet1,vhost=on,fd=4: TUNGETIFF ioctl() >> failed: Inappropriate ioctl for device >> >> Network device arguments passed to qemu-kvm (fd 3 and 4 are the fds >> that Python opened): >> -netdev tap,id=hostnet0,vhost=on,fd=3 3<>/dev/tap5,vhostfd=3 >> -device virtio-net >> pci,netdev=hostnet0,id=net0,mac=52:54:00:01:cb:a5,bus=pci.0,addr=0x3 >> -netdev tap,id=hostnet1,vhost=on,fd=4 4<>/dev/tap24,vhostfd=4 >> -device virtio-net >> pci,netdev=hostnet1,id=net1,mac=52:50:00:1b:ce:6e,bus=pci.0,addr=0x4 >> >> Version: >> QEMU emulator version 2.6.0 (qemu-kvm-ev-2.6.0-28.el7_3.3.1) > > File descriptor passing is optional. Libvirt uses it so that QEMU can > be launched without root privileges. It's a good idea to follow this > practice for production environments or when dealing with untrusted > guests. But remember, it's optional and you can skip fd passing if you > want. > > fd=X and vhostfd=Y are supposed to be different device types: > * fd=X is a tap-like device (either /dev/tapN or macvtap) > * vhostfd=Y is /dev/vhost-net > > Looks like your code is just opening /dev/tapN and using that fd for > both fd=X and vhostfd=Y. This is incorrect and causes the ioctl error. > > Stefan
