Re: [PATCH libvirt v1 0/6] Fix ZPCI address auto-generation on s390

On Thu, 2020-04-09 at 12:30 +0200, Shalini Chellathurai Saroja wrote: I'd have to dig up the old threads, but based on what I remember the behaviors you describe are entirely intentional. For PCI addresses, setting all parts of the address to zero or not setting it at all is equivalent, and we wanted to be consistent with that behavior for ZPCI; additionally, zero is not a valid value for uid so of course neither is the address uid=0 fid=0, which means that we're not preventing the user from specifying a valid address by conflating the all-zero address with the unspecified address. For partially-specified addresses, the behavior is also the same as PCI: any part you don't specify is considered to be zero, which results in uid=0 fid=0 -> uid=0 fid=0 -> address gets autogenerated uid=0 fid=x -> uid=0 fid=x -> address is rejected as invalid uid=0 -> uid=0 fid=0 -> address gets autogenerated fid=x -> uid=0 fid=x -> address is rejected as invalid uid=x -> uid=x fid=0 -> address is accepted So, just like for PCI addresses, you have basically two reasonable options: either don't specify any zPCI address and leave allocation entirely up to libvirt, or specify all of the addresses completely: anything in between will likely not work as you'd expect or want. Again, this is based purely on my recollection of design discussions that happened one and a half years ago, so I might have gotten some of the details wrong - in which case by all means call me out on that O:-) -- Andrea Bolognani / Red Hat / Virtualization