On Wed, 5 Aug 2009, Manuel Lauss wrote: > > On Tue, Aug 04, 2009 at 04:04:16PM -0700, Linus Torvalds wrote: > > > > So I _think_ that you actually are getting the same layout as with 2.6.30, > > but with a warning that didn't exist in 2.6.30. Can you verify? > > You're absolutely correct: /proc/iomem on 2.6.30 and 31-rc5+ are identical, > the only difference being 2.6.30 not complaining about any collisions. Ok. So this is not a regression per se. The warning looks a bit annoying, but in fact I believe that the warning is correct, and is showing us a real problem. Well, not "problem" exactly, but an issue. I think that what is happening is that pci_find_parent_resource() may be in fact finding another parent resource than the one we strictly want (the pre-existing one). And I think it's brought on by the fact that this is a ROM resource. I bet that what is happening is: - the PCI bridge has a _prefetchable_ bus resource window at ff600000-ff6fffff : PCI Bus 0000:02 - the PCI bridge is a transparent bridge - the BIOS has set up the ROM (BAR 6) at ff680000-ff69ffff : 0000:02:03.0 - We have for some reason marked the ROM as being non-prefetchable. and what happens is: - pci_find_parent_resource() refuses to use the ff600000-ff6fffff PCI bridge resource, because it is marked IORESOURCE_PREFETCH, and the ROM resource is not so marked. - But because it's a transparent bridge, once we've iterated over the bridge window resources, we have a couple of resources that point back to the parent of the bridge - the PCI root resources. So now pci_find_parent_resource() will return that instead - request_resource() will (correctly) notice that the root resource already has other resources at that address (the PCI brige window!) and will refuse to insert it - leading us to re-allocating the BIOS-provided resource later (to the non-prefetchable bus window) - but when we for a short while (incorrectly) used 'insert_resource()' in pci_claim_resource(), it would recurse back into the prefetchable window, and everything would work - because a ROM resource is actually perfectly happy to be in a prefetchable window. So I think I understand the behavior on your box, and the warning was actually correct and useful - our PCI layer is being stupid. We should mark ROM resources as being prefetchable. Hmm.. We do seem to _try_ do exactly that in pci_read_bases(). I wonder what I'm missing, and where that bit is then cleared. Or whether we're doing that ROM BAR probe somewhere else too.. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
