Re: [PATCH] docs: add zpci information to pci-addresses.rst

On Tue, 14 Apr 2020 23:06:47 +0200 Boris Fiuczynski <fiuczy(a)linux.ibm.com&gt; 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 :)