Re: [PATCH] qemu: command: Don't attempt to set backend MTU for networks which don't use host backend directly

From: Peter Krempa <pkrempa(a)redhat.com&gt; Attempting to set MTU for network types which don't actually use the network device on the host results in a failure. The 'mtu' property is also used e.g. for the 'host_mtu' property of e.g. 'virtio-net-pci' which is applied even in vhost-user mode. Use the existing switch which selects devices without a network device backend on the host side and skip setting the MTU. Tested by running 'passt' in vhost-user mode manually: passt -f --vhost-user -s /tmp/vh.sock and the following XML: <interface type="vhostuser"> <mac address="52:54:00:3d:91:97"/> <source type="unix" path="/tmp/vh.sock" mode="client"/> <model type="virtio"/> <mtu size="9999"/> <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x0"/> </interface> The OS in the guest reports MTU 9999. Closes: https://gitlab.com/libvirt/libvirt/-/issues/717 Closes: https://gitlab.com/libvirt/libvirt/-/issues/192 Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- src/qemu/qemu_command.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)