On Tue, 24 Jul 2018 10:20:48 +0200 Andrea Bolognani <abologna@xxxxxxxxxx> wrote: > Looking at both the generated QEMU command line and the qemu-devel > message linked above, I seem to understand the zpci device is > basically some sort of adapter that sits between a regular PCI > device (emulated or otherwise) and an s390 guest and presents an > ID-based interface to the latter; so IIUC the s390 guest doesn't > actually see a PCI device, but a couple of IDs that can (somehow) > be used to access the underlying PCI device. > > From whatever little s390 knowledge I have, I recall the > architecture using peculiar ways to address and access devices, so > PCI not being usable wouldn't surprise me that much; what I find > odd, however, is that regular PCI seems to be available at least > on the host side, because otherwise stuff like > > -device zpci,uid=1,fid=1,target=vpci0 > -device vfio-pci,host=0000:00:00.0,id=vpci0 > > wouldn't be possible. So, would anyone with s390 knowledge please > spend a few words explaining how the various pieces fit together? For some hints, let me point to https://virtualpenguins.blogspot.de/2018/02/notes-on-pci-on-s390x.html -- for implementation details, I'll point to the IBM folks :) > > Assuming the above is a correct reading of the situation, it > would seem the IDs are the only guest-visible part that we need > to make sure doesn't change during the lifetime of the guest, > while the usual bus/slot/function triplet assigned to the > underlying PCI device doesn't actually matter. And if that's the > case, wouldn't something like > > <address type='zpci' uid='1' fid='1'/> > > be a better representation of the arrangement? We could leave it > up to QEMU to assign addresses to the PCI devices in this case... > But maybe they still matter for things such as migration? Or maybe > I've just gotten it wrong altogether? :) > -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
