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

On 06/12/2016 10:08 PM, Kevin Zhao wrote: > Hi Cole, > Thanks for your kindly 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 > > 2) 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 > > OK . Hope it will be true in the future. > > > 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> > > But there isn't currently any switch to say 'always give me virtio-pci instead > of virtio-mmio' > > In my opinion, that is to say, when I want to attach a block device to a guest > and hope it > take effects soon,*the only way is using 'scsi' instead of 'virtio'* in > Aarch64 just like what > virt-manager does since scsi supports hot plugged. Am I right? On x86 at least virtio-blk + pci supports hotplug, but I don't know if that combo works for aarch64 at the moment. However disk=scsi hotplug should currently work on aarch64 with controller=virtio-scsi, I've tested that before Thanks, Cole