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Re: [Qemu-devel] [PATCH 6/8] pci: Simpler implementation of primary PCI

From: David Gibson
Subject: Re: [Qemu-devel] [PATCH 6/8] pci: Simpler implementation of primary PCI bus
Date: Wed, 29 May 2013 19:43:41 +1000
User-agent: Mutt/1.5.21 (2010-09-15)

On Thu, May 23, 2013 at 10:16:27PM +1000, David Gibson wrote:
> On Thu, May 23, 2013 at 02:22:30PM +0300, Michael S. Tsirkin wrote:
> > On Thu, May 09, 2013 at 10:31:10AM +1000, David Gibson wrote:
> > > Currently pci_get_primary_bus() searches the list of root buses for one
> > > with domain 0.  But since host buses are always registered with domain 0,
> > > this just amounts to finding the only PCI host bus.
> > > 
> > > This simplifies the implementation by defining the primary PCI bus to
> > > be the first one registered, using a global variable to track it.
> > > 
> > > Signed-off-by: David Gibson <address@hidden>
> > 
> > Or better: can we just fail if there is more than
> > one root?
> That might work, I'll look into doing that.

So, the difficulty with this is that then any machine with multiple
PCI bridges could not use pci_nic_init(), since it calls
pci_get_bus_devfn() which calls pci_find_primary_bus() which would
always fail.  And using pci_nic_init() is more or less mandatory in
the machine_init function to support old-style nic configuration.


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_!

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