From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34973) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WKS86-0006wD-Rv for qemu-devel@nongnu.org; Mon, 03 Mar 2014 07:38:07 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WKS7y-00062E-ED for qemu-devel@nongnu.org; Mon, 03 Mar 2014 07:37:58 -0500 Received: from mail-ea0-x22b.google.com ([2a00:1450:4013:c01::22b]:33788) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WKS7y-00061x-7t for qemu-devel@nongnu.org; Mon, 03 Mar 2014 07:37:50 -0500 Received: by mail-ea0-f171.google.com with SMTP id n15so2992911ead.30 for ; Mon, 03 Mar 2014 04:37:49 -0800 (PST) Date: Mon, 3 Mar 2014 13:37:46 +0100 From: Stefan Hajnoczi Message-ID: <20140303123746.GD21055@stefanha-thinkpad.redhat.com> References: <20140228174019.12875.25127.malonedeb@wampee.canonical.com> <20140228174019.12875.25127.malonedeb@wampee.canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140228174019.12875.25127.malonedeb@wampee.canonical.com> Subject: Re: [Qemu-devel] [Bug 1286253] [NEW] virtio-net acceleration features not set when plugged into backend dynamically List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Bug 1286253 <1286253@bugs.launchpad.net> Cc: qemu-devel@nongnu.org, "Michael S. Tsirkin" 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