Re: [Qemu-devel] [PATCH RFC 1/1] s390x/pci: Extend pci representation by new zpci device

[Frank Blaschka <blaschka@linux.vnet.ibm.com>]

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.

> 
> 
> Alex
>