Re: [Qemu-devel] Help: Does Qemu support virtio-pci for net-device and disk device?

[Kevin Zhao]

Hi Jones:
   Thanks~It is great that Qemu has been working on that :-)

On 18 August 2016 at 00:13, Andrew Jones <address@hidden> wrote:

> On Wed, Aug 17, 2016 at 08:08:11PM +0800, Kevin Zhao wrote:
> > Hi all,
> >      Now I'm investigating net device hot plug and disk hotplug for
> > AArch64. For virtio , the default address is virtio-mmio. After Libvirt
> > 1.3.5, user can explicitly specify the address-type to pci and so libvirt
> > will pass the virtio-pci parameters to the Qemu.
> >      Both my host and guest OS is Debian8, and Qemu version is 2.6.0.
> > Libvirt version is 1.3.5.
> >      For net-device, I change the address-type to pci, and libvirt pass
> the
> > command below:
> >      -device
> > virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:
> 0d:25:25,bus=pci.2,addr=0x1
> >
> >      After booting, the eth0 device disappear(eth0 occur when the address
> > is virtio-mmio),
> > but I can find another net-device enp2s1, also it can't work for dhcp:
> > Running lspci: 02:01.0 Ethernet controller: Red Hat, Inc Virtio network
> > device
> > I'm not sure whether it worked.
> >
> >      For disk device,* when I change the address-type to pci, the whole
> > qemu command is :*
> > https://paste.fedoraproject.org/409553/,  but the VM can not boot
> > successfully. Does Qemu not support device disk of virtio-pci in AArch64
> > just as it in X86_64?
> >      Thanks~Since I am not very familiar with Qemu, really looking
> forward
> > to your response.
> >
> > Best Regards,
> > Kevin Zhao
>
> libvirt 1.3.5 is a bit old. Later versions no longer unconditionally add
> the i82801b11 bridge, which was necessary to use PCI devices with the PCIe
> host bridge mach-virt has. IMO, libvirt and qemu still have a long way to
> go in order to configure a base/standard mach-virt PCIe machine.
>
>
Yeah, I am changing to libvirt 2.1.0, I find that I should use PCI by
manually add
the slots and bus to it.

1) If we want to support both PCIe devices and PCI, then things are messy.
>    Currently we propose dropping PCI support. mach-virt pretty much
>    exclusively uses virtio, which can be set to PCIe mode (virtio-1.0)
> 2) root complex ports, switches (upstream/downstream ports) are currently
>    based on Intel parts. Marcel is thinking about creating generic models.
> 3) libvirt needs to learn how to plug everything together, in proper PCIe
>    fashion, leaving holes for hotplug.
> 4) Probably more... I forget all the different issues we discovered when
>    we started playing with this a few months ago.
>
> The good news is that x86 folk want all the same things for the q35 model.
> mach-virt enthusiasts like us get to ride along pretty much for free.
>
> So, using virtio-pci with mach-virt and libvirt isn't possible right now,
> not without manual changes to the XML. It might be nice to document how to
> manually convert a guest, so developers who want to use virtio-pci don't
> have to abandon libvirt. I'd have to look into that, or ask one of our
> libvirt friends to help. Certainly the instructions would be for latest
> libvirt though.
>
>
As you said,  that means that I can use PCIe as the bus for disk and
net-device.
I will try using pcie in libvirt. I will try the newest version of libvirt.
Do I need to change <address type = 'pcie'> to enable it in AArch64 ?
The pcie bus will  be automatically assigned in libvirt ?


> Finally, FWIW, with a guest kernel of 4.6.4-301.fc24.aarch64. The
> following qemu command line works for me.
> (notice the use of PCIe), and my network interface gets labeled enp0s1.
>
> $QEMU -machine virt-2.6,accel=kvm -cpu host \
>  -m 1024 -smp 1 -nographic \
>  -bios /usr/share/AAVMF/AAVMF_CODE.fd \
>  -device ioh3420,bus=pcie.0,id=pcie.1,port=1,chassis=1 \
>  -device ioh3420,bus=pcie.0,id=pcie.2,port=2,chassis=2 \
>  -device 
> virtio-scsi-pci,disable-modern=off,disable-legacy=on,bus=pcie.1,addr=00.0,id=scsi0
> \
>  -drive file=/home/drjones/.local/libvirt/images/fedora.qcow2,
> format=qcow2,if=none,id=drive-scsi0-0-0-0 \
>  -device scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-
> scsi0-0-0-0,id=scsi0-0-0-0,bootindex=1 \
>  -netdev user,id=hostnet0 \
>  -device virtio-net-pci,disable-modern=off,disable-legacy=on,bus=
> pcie.2,addr=00.0,netdev=hostnet0,id=net0
>
> I prefer always using virtio-scsi for the disk, but a similar command
> line can be used for a virtio-blk-pci disk.
>
> OK great! Because in Openstack Nova ,AArch64 need to realize the hotplug
only with
the virtio bus, so investigate the virtio-pci. :-)
Thanks again!


> Thanks,
> drew
>