On Wed, Mar 06, 2013 at 04:15:28PM +0100, Ján Tomko wrote:
On 03/05/13 11:36, Daniel P. Berrange wrote:
On Mon, Mar 04, 2013 at 02:39:40PM -0500, Laine Stump wrote:
On 03/04/2013 11:51 AM, Ján Tomko wrote:
It would be nice if we could add pci bridges even when there weren't any specified in the XML, but there are too many PCI devices. I don't know what would be the nicest way to do that.
If we auto-assign addresses for un-addressed devices first (your recent patches did that, right? I forget the status of those), *then* auto-create the required bridges (which themselves will need an auto-assigned address), that should just happen.
Of course, if we do that, then we won't have reserved any slots on bus 0 for even a single pci-bridge device, so we'll fail. Is the proper way out of this to always reserve one (or maybe two, for good measure) slots on any given bus to be used only for bridges? That way no matter how out of hand things get, we'll always have a place we can add another bus. (In the case of *lots* of devices, I assume that a device on a nested PCI bridge would be less efficient, and may have some other limitations, but it would be better than nothing. And if the admin was really concerned about that, they could modify their config to explicitly place several bridges directly on bus 0)
Maybe we could reserve the first bus as well?
I don't think we should artifically reserve anything that isn't absolutely required by the underlying machine type.
You'd have todo a 2 pass assignment. First count the number of devices that need to have PCI addresses assigned. Then create the required number of bridges, then assign the addresses.
Which one is better? The reserved slots would make auto-adding bridges on hotplug possible, but I fear the code would be too ugly. On the other hand, 2-pass assignment sounds really easy to do :)
I think we just do the 2-pass auto-assignment. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|