I don't have an x86 setup handy, but looking through the code 'virtio-net-pci' will work but not 'virtio-net-device'. My understanding was the goal is for any backend to plug into any transport on any platform. I'll try an x86 test with 'virtio-net-device' option and see what happens.
Yes I did check the options on host after device is plugged and guest after features are probed, only the MAC feature is set. Thanks, - Mario -----Original Message----- From: qemu-devel-bounces+m.smarduch=samsung....@nongnu.org [mailto:qemu-devel-bounces+m.smarduch=samsung....@nongnu.org] On Behalf Of Michael S. Tsirkin Sent: Monday, March 03, 2014 4:49 AM To: Stefan Hajnoczi Cc: Bug 1286253; qemu-devel@nongnu.org Subject: Re: [Qemu-devel] [Bug 1286253] [NEW] virtio-net acceleration features not set when plugged into backend dynamically On Mon, Mar 03, 2014 at 01:37:46PM +0100, Stefan Hajnoczi wrote: > On Fri, Feb 28, 2014 at 05:40:19PM -0000, Mario Smarduch wrote: > > 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. > > Can you explain in more detail? > > The command-line looks sane. The virtio-net-device instance should > figure out the tap supports offloads. > > Did you try adding a printf to virtio_net_get_features() to see why > the offload features are not being detected? > > Stefan IIUC mmio does not set any feature bits, so you get the fallback behaviour: $ git grep DEFINE_VIRTIO_NET_FEATURES hw/s390x/s390-virtio-bus.c: DEFINE_VIRTIO_NET_FEATURES(VirtIOS390Device, host_featur hw/s390x/virtio-ccw.c: DEFINE_VIRTIO_NET_FEATURES(VirtioCcwDevice, host_features[0]) hw/virtio/virtio-pci.c: DEFINE_VIRTIO_NET_FEATURES(VirtIOPCIProxy, host_features), include/hw/virtio/virtio-net.h:#define DEFINE_VIRTIO_NET_FEATURES(_state, _field) \ But it should work for pci, and certainly does for x86. -- MST
