On Wed, Mar 04, 2015 at 03:49:15PM +0100, Alexander Graf wrote: > > > On 04.03.15 14:44, Frank Blaschka wrote: > > 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. > > Having s390 devices reside on sysbus is probably a bad idea. Instead, > they should be on an s390 specific bus which then can implement hotplug > easily. > > > Alex >
Hm now I get lost ... Do you suggest we should implement a s390 specific device (which is not derived from TYPE_PCI_HOST_BRIDGE) but implements a pci bus so we can attach a pci device to this device?