Which version of QEMU did you use here? Can you still reproduce this problem with the latest version of QEMU (currently v2.9)?
** Changed in: qemu Status: New => Incomplete -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1286253 Title: virtio-net acceleration features not set when plugged into backend dynamically Status in QEMU: Incomplete Bug description: When using indpendent transport and backend in this case virtio-net- device transport, none of the acceleration features are set after guest probes the transport the backend is plugged into. For virtio-net this leads to low throughput/performance. This holds true for virtio-mmio, PCI transports and most likely for others as well (CCW, S390) and other backends Command to run: ./qemu-system-arm -enable-kvm -smp 2 -kernel zImage -dtb ./guest-a15.dtb -m 512 -M vexpress-a15 -cpu cortex-a15 -nographic \ -append "root=/dev/vda rw console=ttyAMA0 rootwait" -drive if=none,file=/mnt/gauss.root,id=vm1 \ -device virtio-blk-device,drive=vm1 -netdev type=tap,id=net0,ifname=tap0 \ -device virtio-net-device,netdev=net0,mac="52:54:00:12:34:58" For x86 same virtio command for network. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1286253/+subscriptions