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 :| -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list