On Tue, Mar 03, 2015 at 09:38:37PM +0100, Alexander Graf wrote: > > > 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 >
I played arround with the idea of having multiple host bridges and this worked well at least for static (non hotplug) configuration. In case I want to hotplug a host bridge I got following error: (qemu) device_add s390-pcihost,fid=8,uid=9 Bus 'main-system-bus' does not support hotplugging Is there anything I have to enable to support this? I have: has_dynamic_sysbus = 1 and cannot_instantiate_with_device_add_yet = false but this seems not to help for the hotplug case. Frank
