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Re: [Qemu-devel] [PATCH 2/2 RFC] s390x/pci: rework pci infrastructure mo

From: Michael S. Tsirkin
Subject: Re: [Qemu-devel] [PATCH 2/2 RFC] s390x/pci: rework pci infrastructure modeling
Date: Thu, 12 Mar 2015 10:26:29 +0100

On Thu, Mar 12, 2015 at 09:46:44AM +0100, Frank Blaschka wrote:
> On Wed, Mar 11, 2015 at 03:57:05PM +0100, Michael S. Tsirkin wrote:
> > On Wed, Mar 11, 2015 at 03:38:44PM +0100, Frank Blaschka wrote:
> > > I like Alex's idea because:
> > > 1) It reflects pretty well the actual nature of the pci system in real 
> > > s390 hw
> > 
> > why do you say this? does real hw has this
> > one device per bridge limit?
> > 
> Actually we don't know. HW does not expose this information. All we know is 
> each
> pci function is completely separated. So it is a good assumption to have a 
> separate
> bridge/bus for each pci function. By the way the Linux kernel for s390 makes 
> the
> same assumption by creating a new pci domain for each function. You may want
> to read the cover letter again to get more technical details on this.

I'm sorry, my question wasn't clear.
I'll try to rephrase.
Imagine that I'm using s390, and I add a pci to pci bridge:

-device s390-pcihost,fid=17,uid=2217,id=mydev
-device ne2k_pci,bus=mydev.0,addr=0
-device pci-bridge,chassis_nr=2,bus=bus=mydev.0,addr=0,id=newdev
-device ne2k_pci,bus=newdev,addr=8

What happens with your scheme then?

It seems reasonable to assume that this is a legal configuration on real


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