Re: [libvirt] Question about virtio-pci in Aarch64

On 08/17/2016 07:49 AM, Kevin Zhao wrote: > Hi Cole, > Long time no see~ > Thanks for giving help me about AArch64 of virtio-pci. You have rich > experience about this, > I am green hand and seeking for your help again :-) > Hello again, happy to help :) > On 13 June 2016 at 06:21, Cole Robinson <crobinso(a)redhat.com > <mailto:crobinso@redhat.com>> wrote: > > On 06/12/2016 10:29 AM, Kevin Zhao wrote: > > Hi Cole && All, > > Nice meeting you in the libvirt mail-list. Greetings from Linaro !!! > > I am Kevin Zhao from Linaro and working for OpenStack on Aarch64. > > Nowadays I find that the default "virtio" bus is "virtio-mmio" , not > > "virtio-pci". Since virtio-mmio do not has the host plugged function , > > something is wrong with the function in OpenStack Nova. > > > > Then I search and find some mail information as belows by Cole :-) > > 1) https://www.redhat.com/archives/libvir-list/2015- December/msg00217.html > <https://www.redhat.com/archives/libvir-list/2015- December/msg00217.html> > > 2) https://www.redhat.com/archives/libvir-list/2016- March/msg00167.html > <https://www.redhat.com/archives/libvir-list/2016- March/msg00167.html> > > > > I see some efforts have been doing by you. Really thanks for your > > efforts for Aarch64. And I have some small questions. > > 1. Is Libvirt planning to replace the default virtio-mmio to virtio-pci > > for Aarch64? > > We have vague plans to maybe change the virtio-mmio default to virtio-pci at > some future point, based on some new enough qemu machine type. But the main > blocker is that most linux distributions currently don't work out of the box > with virtio-pci, at least Fedora doesn't as far as I know. So changing the > default now is pre-mature > > > 2. If not , how can I change the xml file(generated by Virsh) for > > virtio-pci so that Qemu can recognize it ? > > > > The latest libvirt-1.3.5 release accepts device XML containing <address > type='pci'/> . The address block is an explicit request to libvirt to > 'allocate a PCI address' rather than the default virtio-mmio. So for example > if you want to specify a virtio nic, but have it use virtio-pci rather than > virtio-mmio, you can do something like: > > <interface type='network'> > <source network='default'/> > <model type='virtio'/> > <address type='pci'/> > </interface> > > > I have changed the libvirt to 1.3.5 now, also add the pci to net-device xml like: > <address type='pci'/>,then use the virsh to boot the VM,the total xml file is: > https://paste.fedoraproject.org/409534/71434141/ > > After booting, the eth0 device disappear(eth0 occur when the address is > virtio-mmio), > but I can find another net-device, also it can't work for dhcp: > 2: enp2s1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state > UP group default qlen 1000 > link/ether 52:54:00:0d:25:26 brd ff:ff:ff:ff:ff:ff > inet6 fe80::5054:ff:fe0d:2526/64 scope link > valid_lft forever preferred_lft forever > Running lspci: > 02:01.0 Ethernet controller: Red Hat, Inc Virtio network device > > My question is: > 1. I use Debian 8 AArch64 as the Guest OS, do you think the virtio-pci for > net-device works is OK ? > My guess is that the support isn't complete. Last I checked Fedora doesn't even work with aarch64 virtio-pci + uefi, because it requires some kernel changes that haven't been fully upstreamed yet. But that was several months ago... There may be a way to work around it nowadays but I don't personally know. You may want to test with either RHELSA if you have a copy, or linaro images.

> 2. If I change the disk address-type to pci(Libvirt pass the virtio pci > parameters to Qemu for disk device), but I can't boot > the VM. Does Qemu not support virtio pci for disk device in AArch64? > That should work fine in my testing with RHELSA, so I don't think it's a libvirt or qemu limitation. Probably the guest OS + UEFI. - Cole > Big Big Thanks~ > > > But there isn't currently any switch to say 'always give me virtio-pci instead > of virtio-mmio' > > - Cole > >