On Tue, 14 Apr 2020 23:06:47 +0200 Boris Fiuczynski <fiuczy@linux.ibm.com> wrote:
On 4/15/20 12:51 PM, Cornelia Huck wrote:
+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.
Not sure how much is autogenerated; however, as this document talks about how pci addresses in the xml translate to pci addresses in the guest, I think we can simply ignore it?
+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.
Hm, is it intentional that this does not show up in the actual pci address? But maybe I'm confused.
+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.
Do you want to explain the fid/slot stuff in a patch on top? Despite your attempts at time travel, this patch has already been pushed :)