[libvirt-users] pcie-expander-bus doesn't support pcie-pci-bridge and pcie-switch-upstream-port

[Han Han]

In libvirt, I found pcie-expander-bus controller doesn't support
pcie-to-pci-bridge and pcie-switch-upstream-port.

Version: libvirt-4.9

# cat /tmp/c.xml
...
    <controller type='pci' index='0' model='pcie-root'/>
    <controller type='pci' index='1' model='pcie-expander-bus'>
      <model name='pxb-pcie'/>
      <target busNr='3'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03'
function='0x0'/>
    </controller>
    <controller type='pci' index='2' model='pcie-to-pci-bridge'>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00'
function='0x0'/>
    </controller>
...
# virsh -k0 -K0 define
/tmp/c.xml

error: Failed to define domain from /tmp/c.xml
error: XML error: The device at PCI address 0000:01:00.0 cannot be plugged
into the PCI controller with index='1'. It requires a controller that
accepts a pcie-to-pci-bridge.

# cat /tmp/b.xml
...
    <controller type='pci' index='0' model='pcie-root'/>
    <controller type='pci' index='1' model='pcie-expander-bus'>
      <model name='pxb-pcie'/>
      <target busNr='3'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03'
function='0x0'/>
    </controller>
    <controller type='pci' index='2' model='pcie-switch-upstream-port'>
      <model name='x3130-upstream'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00'
function='0x0'/>
    </controller>
...
# virsh -k0 -K0 define /tmp/b.xml
error: Failed to define domain from /tmp/b.xml
error: XML error: The device at PCI address 0000:01:00.0 cannot be plugged
into the PCI controller with index='1'. It requires a controller that
accepts a pci-switch-upstream-port.

In function virDomainPCIAddressBusSetModel, I find pcie-expander-bus only
supports pcie-root-port and dmi-to-pci-bridge
   353     case
VIR_DOMAIN_CONTROLLER_MODEL_PCIE_EXPANDER_BUS:
   354     ┆   /* 32 slots, no hotplug, only accepts pcie-root-port
or
   355     ┆   ┆*
dmi-to-pci-bridge
   356     ┆
┆*/
   357     ┆   bus->flags = (VIR_PCI_CONNECT_TYPE_PCIE_ROOT_PORT
|
   358     ┆   ┆   ┆   ┆   ┆
VIR_PCI_CONNECT_TYPE_DMI_TO_PCI_BRIDGE);
   359     ┆   bus->minSlot =
0;
   360     ┆   bus->maxSlot =
VIR_PCI_ADDRESS_SLOT_LAST;
   361     ┆   break;

But it works in qemu:
# /usr/libexec/qemu-kvm -machine q35 -m 1024 -device
pxb-pcie,bus_nr=250,id=pci.1,bus=pcie.0,addr=0x4 -device
pcie-pci-bridge,id=pci.250,bus=pci.1,addr=0x0 -device
pcie-pci-bridge,id=pci.251,bus=pci.1,addr=0x1 -spice
port=5902,addr=0.0.0.0,disable-ticketing /var/lib/libvirt/images/q35.qcow2

So why pcie-expander-bus doesn't these two controllers? For any concerns in
libvirt?
Thank you~


-- 
Best regards,
-----------------------------------
Han Han
Quality Engineer
Redhat.

Email: hhan at redhat.com
Phone: +861065339333
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