On 03.03.15 14:25, Frank Blaschka wrote: > On Tue, Mar 03, 2015 at 10:33:05AM +0100, Alexander Graf wrote: >> >> >> >>> Am 03.03.2015 um 09:06 schrieb Frank Blaschka <blasc...@linux.vnet.ibm.com>: >>> >>>> On Thu, Feb 26, 2015 at 04:34:06PM +0100, Alexander Graf wrote: >>>> >>>> >>>>> On 26.02.15 16:27, Frank Blaschka wrote: >>>>>> On Thu, Feb 26, 2015 at 03:39:15PM +0100, Alexander Graf wrote: >>>>>> >>>>>> >>>>>>> On 26.02.15 12:59, Frank Blaschka wrote: >>>>>>> This patch extends the current s390 pci implementation to >>>>>>> provide more flexibility in configuration of s390 specific >>>>>>> device handling. For this we had to introduce a new facility >>>>>>> (and bus) to hold devices representing information actually >>>>>>> provided by s390 firmware and I/O configuration. >>>>>>> >>>>>>> On s390 the physical structure of the pci system (bridge, bus, slot) >>>>>>> in not shown to the OS. For this the pci bridge and bus created >>>>>>> in qemu can also not be shown to the guest. The new zpci device class >>>>>>> represents this abstract view on the bare pci function and allows to >>>>>>> provide s390 specific configuration attributes for it. >>>>>>> >>>>>>> Sample qemu configuration: >>>>>>> -device e1000,id=zpci1 >>>>>>> -device ne2k_pci,id=zpci2 >>>>>>> -device zpci,fid=2,uid=1248,pci_id=zpci1 >>>>>>> -device zpci,fid=17,uid=2244,pci_id=zpci2 >>>>>>> >>>>>>> A zpci device references the corresponding PCI device via device id. >>>>>>> The new design allows to define multiple host bridges and support more >>>>>>> pci devices. >>>>>> >>>>>> Isn't this reverse? Shouldn't it rather be >>>>>> >>>>>> -device zpci,...,id=zpci1 >>>>>> -device e1000,bus=zpci1.0 >>>>>> >>>>>> with a limit on each virtual zpci bus to only support one device? >>>>> >>>>> Do you mean something like having multiple host bridges (providing a pci >>>>> bus >>>>> each) and limit the bus to just one device? >>>>> >>>>> -device s390-pcihost,fid=16,uid=1234 >>>>> -device s390-pcihost,fid=17,uid=5678 >>>>> -device e1000,bus=pci.0 >>>>> -device ne2k_pci,bus=pci.1 >>>>> >>>>> We also discussed this option but we don't like the idea to put attributes >>>>> belong to the pci device to the host bridge. >>>> >>>> I guess I'm not grasping something obvious here :). What exactly are the >>>> attributes again? >>> Sorry for the late response, I was on vacation the last couple days. >>> >>> The fid and uid values are provided by microcode/io layer on the real >>> hardware. >> >> So they are arbitrary numbers? What uniqueness constraints do we have on >> them? > fid and uid must be unique within the same qemu. At a first look the numbers > are > arbitrary but our configuration folks want explicitly define a particular fid > and uid > to better support migration and pass-through scenarios.
Well, at the end of the day you want to make sure they're identical on both sides, yes. >> IIUC you can only have a single pcie device behind a virtual "bus" anyway, >> so what if we just calculate uid and fid from the bus id? > I think this similar to the current implementation. We use the slot (idea for > the future was > bus + slot) to generate uid and fid. But this is not flexible enough. As I > said, our > configuration folks want to be able to specify fid and uid for the device. I don't see how this is different from what PPC does with its LIOBN which is a property of the PHB. Alex
