From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43317) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aLBCM-0006cN-0U for qemu-devel@nongnu.org; Mon, 18 Jan 2016 09:54:26 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aLBCH-0004e5-Be for qemu-devel@nongnu.org; Mon, 18 Jan 2016 09:54:25 -0500 Received: from mail-wm0-x22f.google.com ([2a00:1450:400c:c09::22f]:37174) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aLBCG-0004e1-Rw for qemu-devel@nongnu.org; Mon, 18 Jan 2016 09:54:21 -0500 Received: by mail-wm0-x22f.google.com with SMTP id n5so67879351wmn.0 for ; Mon, 18 Jan 2016 06:54:20 -0800 (PST) References: <1452522868-25550-1-git-send-email-peter.maydell@linaro.org> <1452522868-25550-5-git-send-email-peter.maydell@linaro.org> <569CE8AC.8010105@linaro.org> <569CEF51.3070203@linaro.org> From: Eric Auger Message-ID: <569CFC8D.6050206@linaro.org> Date: Mon, 18 Jan 2016 15:54:05 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PULL 5/5] hw/arm/virt: Support legacy -nic command line syntax List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell Cc: Christoffer Dall , Alex Williamson , "eric.auger@st.com" , QEMU Developers , Ashok Kumar On 01/18/2016 03:14 PM, Peter Maydell wrote: > On 18 January 2016 at 13:57, Eric Auger wrote: >> Hi Peter, >> On 01/18/2016 02:34 PM, Peter Maydell wrote: >>> Hmm, I guess this is changing things in that we now will have a >>> virtio PCI device appearing if you use the default (-net nic -net user) >>> settings. But I don't see why that would particularly interfere >>> with VFIO passthrough, except in as much as the guest now has >>> two network cards in it and might be preferring one as eth0 >>> rather than the other... >> Yes that's what currently happens I think. I get the slirp thing on eth0 >> and my passthrough'ed device on eth1. That's not very straightforward >> for the end-user to get those 2 NIC's now. In case I passthrough some >> NIC's I would have expected this default NIC not be instantiated? > > The QEMU networking layer only knows about networking controlled > by the -net or -netdev options (and in those cases it does disable > the default network device). Because the back-end for passthrough > NICs is completely unknown to QEMU (it is all done in hardware), > I'm not sure we have any way to know that the thing you've passed through > is a NIC and not some other random PCI device... > >> Alex, how do you manage on x86 platforms with VFIO-PCI NIC? > > ...but presumably the x86 folks have been here before us > and know how this should work :-) Yes. maybe we could create a new network backend VFIO and use that kind of cmd line: NET_OPTIONS="-netdev VFIO,id=myeth0 \ -device vfio-amd-xgbe,host=e0900000.xgmac,netdev=myeth0" In the specialized VFIO-Platform device I can easily add a dummy NICConf field and add static Property amd_xgbe_properties[] = { DEFINE_NIC_PROPERTIES(VFIOAmdXgbeDevice, conf), DEFINE_PROP_END_OF_LIST(), }; But it complexifies the user command line quite a lot and not sure it is worth the candle? Thanks Eric > > thanks > -- PMM >