On Fri, Jan 27 2023, Sebastian Mitterle <smitt...@redhat.com> wrote: > Add some documentation about the zpci device and how > to use it with pci devices on s390x. > > Used source: Cornelia Huck's blog post > https://people.redhat.com/~cohuck/2018/02/19/notes-on-pci-on-s390x.html > > Signed-off-by: Sebastian Mitterle <smitt...@redhat.com> > --- > v2: move section below 'Device support' > --- > docs/system/s390x/pcidevices.rst | 34 ++++++++++++++++++++++++++++++++ > docs/system/target-s390x.rst | 1 + > 2 files changed, 35 insertions(+) > create mode 100644 docs/system/s390x/pcidevices.rst > > diff --git a/docs/system/s390x/pcidevices.rst > b/docs/system/s390x/pcidevices.rst > new file mode 100644 > index 0000000000..fec905d6e6 > --- /dev/null > +++ b/docs/system/s390x/pcidevices.rst > @@ -0,0 +1,34 @@ > +PCI devices on s390x > +==================== > + > +PCI devices on s390x work differently than on other architectures.
add "and need to be configured in a slightly different way." ? > + > +To start with, using a PCI device requires the additional ``zpci`` device. > For example, I think the "zpci" device is not technically "required" (ISTR that we autogenerate it, if needed); however, you need it if you actually want to specify uid/fid/... what about: "Every PCI device is linked with an additional ``zpci`` device. While the ``zpci`` device will be autogenerated if not specified, it is recommended to specify it explicitly so that you can pass s390-specific PCI configuration." ? > +in order to pass a PCI device ``0000:00:00.0`` through you'd specify:: > + > + qemu-system-s390x ... \ > + -device zpci,uid=1,fid=0,target=hostdev0,id=zpci1 \ > + -device vfio-pci,host=0000:00:00.0,id=hostdev0 > + > +Here, the zpci device is joined with the PCI device via the ``target`` > property. > + > +Note that we don't set bus, slot or function here for the guest as is common > in other > +PCI implementations. Topology information is not available on s390x. > Instead, ``uid`` "Topology information is not available on s390x, and the guest will not see any of the bus/slot/function information specified on the command line." ? > +and ``fid`` determine how the device is presented to the guest operating > system. > + > +In case of Linux, ``uid`` will be used in the ``domain`` part of the PCI > identifier, and > +``fid`` identifies the physical slot, i.e.:: > + > + qemu-system-s390x ... \ > + -device zpci,uid=7,fid=8,target=hostdev0,id=zpci1 \ > + ... > + > +will be presented in the guest as:: > + > + # lspci -v > + 0007:00:00.0 ... > + Physical Slot: 00000008 > + ... > + > +Finally, note that you might have to enable the ``zpci`` feature in the cpu > model in oder to use > +it. I'm wondering what the current state of that feature is -- is it present by default in the newer named models? (My original blog entry was written nearly five years ago ;)
