[libvirt] [PATCH 33/34] Auto-assign PCI addresses

Daniel P. Berrange berrange at redhat.com
Sat Jan 16 14:52:11 UTC 2010

On Fri, Jan 15, 2010 at 09:05:44PM +0100, Daniel Veillard wrote:
> On Fri, Jan 08, 2010 at 05:23:29PM +0000, Daniel P. Berrange wrote:
> > Instead of relying on QEMU to assign PCI addresses and then querying
> > them with 'info pci', manually assign all PCI addresses before starting
> > the guest.  These addresses are not stable across reboots. That will
> > come in a later patch
> > 
> > NB, the PIIX3 (IDE, FDC, ISA-Bridge) will always have slot 1 and
> > VGA will always have slot 2. We declare the Virtio Balloon gets
> > slot 3, and then all remaining slots are for configured devices.
>   Just wondering, how many slot is there, and shouldn't we try to
> keep a couple of reserved slots there for future needs, not important
> now but if we want to make them stable later that may be needed then

We're quite short on PCI slots currently - QEMU only has a single PCI domain
with a single PCI bus. That gives 32 slots max. Since NICs and Virtio Disks
each require 1 slot per device I don't want to reserve any more than are
absolutely neccessary. We need to encourage QEMU developers to add further
PCI buses or domains which would give us 100's of slots

Or encourage them to create a VirtIO disk controller, so can we make more
efficient usage of slots.

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