[Qemu-devel] virtio-net-pci possible limitation on AArch64

[Alexandru Avadanii]

Hi,
I ran into an interesting limitation (or possibly bug) while trying to attach 
more than 3 (three) virtio-net-pci NICs to an AArch64 guest.
I created 4 network with virsh (see below for xml defitions) - nothing fancy, 
only 2 of them use NAT.

Attaching a virtio-net-pci NIC for each network works well, VMs can be spawned, 
all devices are properly detected by the guest OS.
The first 3 guest interfaces work perfectly, however I can't get any traffic on 
the 4th one (in my case the public one).

QEMU version: 2.9.0
Libvirt: tested with both 1.3.4 and 3.5.0, although I don't think libvirt is to 
blame here
Host OS: Ubuntu Xenial 16.04.2 LTS
Guest OS: Ubuntu Xenial Cloud Image (latest available)
Reproducibility rate: 100% with below config

VM is created with (also domain XML attached at the end of this mail):
$ virt-install --name cfg01 --ram 4096 --vcpus 6 --cpu host-passthrough 
--accelerate \
--network network:pxe,model=virtio-net-pci \
--network network:mgmt,model=virtio-net-pci \
--network network:internal,model=virtio-net-pci \
--network network:public,model=virtio-net-pci \
--console pty --autostart --noreboot --noautoconsole --video=vga 
--noautoconsole [...]

You might notice I had to disable legacy virtio in the domain XML, or the guest 
would complain about a missing F_... property and no guest network interfaces 
would be detected.

For now, since we only need 4 guest interfaces, we switched one of them back to 
virtio-mmio, and everything is working as expected.
Unfortunately I can't investigate this myself right now, but I can provide 
additional details if needed for someone else to look into it.

BR,
Alex

---
Network definitions:
---
<network>
  <name>pxe</name>
  <forward mode='nat'/>
  <bridge name='pxe' stp='on' delay='0'/>
  <ip address='192.168.10.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.10.100' end='192.168.10.254'/>
    </dhcp>
  </ip>
</network>

<network>
  <name>mgmt</name>
  <bridge name='mgmt' stp='on' delay='0'/>
  <ip address='172.16.10.1' netmask='255.255.255.0'>
  </ip>
</network>

<network>
  <name>internal</name>
  <bridge name='internal' stp='on' delay='0'/>
</network>

<network>
  <name>public</name>
  <forward mode='nat'/>
  <bridge name='public' stp='on' delay='0'/>
  <ip address='10.16.0.1' netmask='255.255.255.0'>
  </ip>
</network>

---
Domain XML:
---
<domain type='kvm' id='28' 
xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
  <name>cfg01</name>
  <uuid>3f8415d1-963a-46aa-8a63-1c6558775b92</uuid>
  <memory unit='KiB'>4194304</memory>
  <currentMemory unit='KiB'>4194304</currentMemory>
  <vcpu placement='static'>6</vcpu>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='aarch64' machine='virt-2.9'>hvm</type>
    <loader readonly='yes' type='pflash'>/usr/share/AAVMF/AAVMF_CODE.fd</loader>
    <nvram>/var/lib/libvirt/qemu/nvram/cfg01_VARS.fd</nvram>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <gic version='3'/>
  </features>
  <cpu mode='host-passthrough' check='none'/>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <devices>
    <emulator>/usr/bin/kvm</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='none' io='native'/>
      <source 
file='/home/jenkins/alav/armband/upstream/fuel/mcp/scripts/images/mcp_cfg01.qcow2'/>
      <backingStore/>
      <target dev='vda' bus='virtio'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x04' slot='0x00' 
function='0x0'/>
    </disk>
    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source 
file='/home/jenkins/alav/armband/upstream/fuel/mcp/scripts/images/mcp_cfg01.iso'/>
      <backingStore/>
      <target dev='sda' bus='scsi'/>
      <readonly/>
      <alias name='scsi0-0-0-0'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>
    <controller type='scsi' index='0' model='virtio-scsi'>
      <alias name='scsi0'/>
      <address type='pci' domain='0x0000' bus='0x03' slot='0x00' 
function='0x0'/>
    </controller>
    <controller type='pci' index='0' model='pcie-root'>
      <alias name='pcie.0'/>
    </controller>
    <controller type='pci' index='1' model='dmi-to-pci-bridge'>
      <model name='i82801b11-bridge'/>
      <alias name='pci.1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' 
function='0x0'/>
    </controller>
    <controller type='pci' index='2' model='pci-bridge'>
      <model name='pci-bridge'/>
      <target chassisNr='2'/>
      <alias name='pci.2'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' 
function='0x0'/>
    </controller>
    <controller type='pci' index='3' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='3' port='0x10'/>
      <alias name='pci.3'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0' 
multifunction='on'/>
    </controller>
    <controller type='pci' index='4' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='4' port='0x11'/>
      <alias name='pci.4'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' 
function='0x1'/>
    </controller>
    <controller type='pci' index='5' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='5' port='0x12'/>
      <alias name='pci.5'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' 
function='0x2'/>
    </controller>
    <interface type='network'>
      <mac address='52:54:00:ae:48:81'/>
      <source network='pxe' bridge='pxe'/>
      <target dev='vnet0'/>
      <model type='virtio-net-pci'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x02' slot='0x01' 
function='0x0'/>
    </interface>
    <interface type='network'>
      <mac address='52:54:00:36:2c:a9'/>
      <source network='mgmt' bridge='mgmt'/>
      <target dev='vnet1'/>
      <model type='virtio-net-pci'/>
      <alias name='net1'/>
      <address type='pci' domain='0x0000' bus='0x02' slot='0x02' 
function='0x0'/>
    </interface>
    <interface type='network'>
      <mac address='52:54:00:43:ce:03'/>
      <source network='internal' bridge='internal'/>
      <target dev='vnet2'/>
      <model type='virtio-net-pci'/>
      <alias name='net2'/>
      <address type='pci' domain='0x0000' bus='0x02' slot='0x03' 
function='0x0'/>
    </interface>
    <interface type='network'>
      <mac address='52:54:00:37:e6:0e'/>
      <source network='public' bridge='public'/>
      <target dev='vnet3'/>
      <model type='virtio-net-pci'/>
      <alias name='net3'/>
      <address type='pci' domain='0x0000' bus='0x02' slot='0x04' 
function='0x0'/>
    </interface>
    <serial type='pty'>
      <source path='/dev/pts/0'/>
      <target port='0'/>
      <alias name='serial0'/>
    </serial>
    <console type='pty' tty='/dev/pts/0'>
      <source path='/dev/pts/0'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
    </console>
    <graphics type='vnc' port='5900' autoport='yes' listen='127.0.0.1'>
      <listen type='address' address='127.0.0.1'/>
    </graphics>
    <video>
      <model type='vga' vram='16384' heads='1' primary='yes'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x02' slot='0x05' 
function='0x0'/>
    </video>
  </devices>
  <seclabel type='dynamic' model='apparmor' relabel='yes'>
    <label>libvirt-3f8415d1-963a-46aa-8a63-1c6558775b92</label>
    <imagelabel>libvirt-3f8415d1-963a-46aa-8a63-1c6558775b92</imagelabel>
  </seclabel>
  <seclabel type='dynamic' model='dac' relabel='yes'>
    <label>+113:+115</label>
    <imagelabel>+113:+115</imagelabel>
  </seclabel>
  <qemu:commandline>
    <qemu:arg value='-global'/>
    <qemu:arg value='virtio-pci.disable-legacy=on'/>
  </qemu:commandline>
</domain>