Sorry about the time travel. I will try to give up that super power... :( On 4/14/20 11:06 PM, Boris Fiuczynski wrote:
On 4/15/20 12:51 PM, Cornelia Huck wrote:
Add some information on how pci address work on s390x.
Signed-off-by: Cornelia Huck <cohuck@redhat.com> Conny, thanks for catching this "wacky case"... :) I took the liberty to remove "completely" because there needs to be room for pci multifunction support... :D
--- docs/pci-addresses.rst | 63 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+)
diff --git a/docs/pci-addresses.rst b/docs/pci-addresses.rst index 923783a151b0..9e241a24fcfb 100644 --- a/docs/pci-addresses.rst +++ b/docs/pci-addresses.rst @@ -184,3 +184,66 @@ guest OS rather than as ``0001:08:00.1``, which is the address of the device on the host. Of course, all the rules and behaviors described above still apply. + +zPCI addresses +============== + +For s390x machines, PCI addresses are handled yet differently. No +topology information is relayed in the PCI addresses; instead, the +``fid`` and ``uid`` elements of the ``zpci`` device convey information. Should it be mentioned that qemu uses the pci address internally to plug the device into its pci bus since the pci address as far as I know must still be properly provided or generated.
+In the simplest case, the following XML snippet + +:: + + <controller type='pci' index='0' model='pci-root'/> + <controller type='pci' index='1' model='pci-bridge'> + <model name='pci-bridge'/> + <target chassisNr='1'/> + <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'> + <zpci uid='0x0002' fid='0x00000001'/> + </address> + </controller> + <interface type='bridge'> + <mac address='02:ca:fe:fa:ce:04'/> + <source bridge='virbr0'/> + <model type='virtio'/> + <address type='pci' domain='0x0000' bus='0x01' slot='0x01' function='0x0'> + <zpci uid='0x0001' fid='0x00000000'/> + </address> + </interface> + +will result in the following in a Linux guest:: + + 0001:00:00.0 Ethernet controller: Red Hat, Inc. Virtio network device + +Note that the PCI bridge is not visible in the guest; s390x always has a flat +topology. + +Neither are any changes in the PCI address visible in the guest; replacing +the PCI address for the virtio-net device with + +:: + + <address type='pci' domain='0x0000' bus='0x01' slot='0x07' function='0x3'> + +will result in the exactly same view in the guest, as the addresses there +are generated from the information provided via the ``zpci`` element (in +fact, from the ``uid``). + This explains that the uid is used by the guest to define the pci domain of the guest device. How about an addition for the fid? Something like:
The function id 'fid' defines the slot address of the pci card in the guest. It can be observed in the guest at /sys/bus/pci/slots. In the example given above the card would be at /sys/bus/pci/slots/00000000.
+Therefore, replacing the virtio-net device definition with the following XML +snippet + +:: + + <interface type='bridge'> + <mac address='02:ca:fe:fa:ce:04'/> + <source bridge='virbr0'/> + <model type='virtio'/> + <address type='pci' domain='0x0000' bus='0x01' slot='0x07' function='0x3'> + <zpci uid='0x0007' fid='0x00000003'/> + </address> + </interface> + +will yield the following result in a Linux guest:: + + 0007:00:00.0 Ethernet controller: Red Hat, Inc. Virtio network device
and the card would be at /sys/bus/pci/slots/00000003.
-- Mit freundlichen Grüßen/Kind regards Boris Fiuczynski IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Gregor Pillen Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen Registergericht: Amtsgericht Stuttgart, HRB 243294