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Date: Sun, 21 Nov 2010 22:39:31 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] Re: [PATCH] PCI: Bus number from the bridge, not
	the device
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To: Gleb Natapov <gleb@redhat.com>
Cc: Isaku Yamahata <yamahata@valinux.co.jp>, Alex Williamson <alex.williamson@redhat.com>, Markus Armbruster <armbru@redhat.com>, qemu-devel@nongnu.org

On Sun, Nov 21, 2010 at 09:29:59PM +0200, Gleb Natapov wrote:
> > We can control the bus numbers that the BIOS will assign to pci root.
> And if you need to insert device that sits behind pci-to-pci bridge? Do
> you want to control that bus address too? And bus number do not unambiguously
> describe pci root since two roots can have same bus number just fine.

They have to have different segment numbers.

> > It's probably required to make them stable anyway.
> > 
> Why?

To avoid bus renumbering on reboot after you add a pci-to-pci bridge.

-- 
MST