Re: [Qemu-devel] [PATCH] Correctly assign PCI domain numbers

[Michael S. Tsirkin]

On Mon, Aug 01, 2011 at 11:33:37PM +1000, David Gibson wrote:
> On Mon, Aug 01, 2011 at 01:10:38PM +0300, Michael S. Tsirkin wrote:
> > On Mon, Aug 01, 2011 at 04:51:02PM +1000, David Gibson wrote:
> > > qemu already almost supports PCI domains; that is, several entirely
> > > independent PCI host bridges on the same machine.  However, a bug in
> > > pci_bus_new_inplace() means that every host bridge gets assigned domain
> > > number zero and so can't be properly distinguished.  This patch fixes the
> > > bug, giving each new host bridge a new domain number.
> > > 
> > > Signed-off-by: David Gibson <address@hidden>
> > 
> > OK, but I'd like to see the whole picture.
> > How does the guest detect multiple domains,
> > and how does it access them?
> 
> For the pseries machine, which is what I'm concerned with, each host
> bridge is advertised through the device tree passed to the guest.

Could you explain please?
What generates the device tree and passes it to the guest?

> That gives the necessary handles and addresses for accesing config
> space and memory and IO windows for each host bridge.

I see. I think maybe a global counter in the common code
is not exactly the best solution in the general case.


> -- 
> David Gibson                  | I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au        | minimalist, thank you.  NOT _the_ 
> _other_
>                               | _way_ _around_!
> http://www.ozlabs.org/~dgibson