On Mon, Jun 21, 2021 at 01:49:04PM +0200, Hans de Goede wrote: > Hi Bjorn, > > On 6/17/21 12:57 AM, Bjorn Helgaas wrote: > > On Wed, Jun 16, 2021 at 08:43:12PM +0200, Hans de Goede wrote: > >> On 6/15/21 10:23 PM, Bjorn Helgaas wrote: > >>> On Tue, Jun 15, 2021 at 12:25:55PM +0200, Hans de Goede wrote: > > > >> I've 2 dmesgs from runs both with and without pci=nocrs, the one > >> with a clean kernel commandline (no special options) yields: > >> > >> [ 0.312333] pci_bus 0000:00: root bus resource [io 0x0000-0x0cf7 window] > >> [ 0.312335] pci_bus 0000:00: root bus resource [io 0x0d00-0xffff window] > >> [ 0.312336] pci_bus 0000:00: root bus resource [mem 0x000a0000-0x000bffff window] > >> [ 0.312337] pci_bus 0000:00: root bus resource [mem 0x65400000-0xbfffffff window] > >> [ 0.312338] pci_bus 0000:00: root bus resource [bus 00-fe] > >> > >> Where as the one with pci=nocrs on the kernel commandline gives: > >> > >> [ 0.271766] pci_bus 0000:00: root bus resource [io 0x0000-0xffff] > >> [ 0.271767] pci_bus 0000:00: root bus resource [mem 0x00000000-0x7fffffffff] > >> [ 0.271768] pci_bus 0000:00: root bus resource [bus 00-fe] > >> > >> Hmm, so assuming that you are right that pci=nocrs only influences > >> the root resources (and I believe you are), and given that the problem is > >> that we are getting these errors: > >> > >> [ 0.655335] pci 0000:00:15.0: BAR 0: no space for [mem size 0x00001000 64bit] > >> [ 0.655337] pci 0000:00:15.0: BAR 0: failed to assign [mem size 0x00001000 64bit] > >> [ 0.655339] pci 0000:00:15.1: BAR 0: no space for [mem size 0x00001000 64bit] > >> [ 0.655340] pci 0000:00:15.1: BAR 0: failed to assign [mem size 0x00001000 64bit] > >> [ 0.655342] pci 0000:00:1f.5: BAR 0: no space for [mem size 0x00001000] > >> > >> Instead of getting this: > >> > >> [ 0.355716] pci 0000:00:15.0: BAR 0: assigned [mem 0x29c000000-0x29c000fff 64bit] > >> [ 0.355783] pci 0000:00:15.1: BAR 0: assigned [mem 0x29c001000-0x29c001fff 64bit] > >> > >> So now I believe that my initial theory for this is probably completely wrong; and > >> I wonder if the issue is that the _CRS returned root IOMEM window is big enough > >> to exactly hold the BIOS assigned mappings, but it does not have any free space > >> allowing the kernel to assign space for the 0000:00:15.0 and 0000:00:15.1 > >> devices ? > >> > >> Assuming that that theory is right, how could we work around this problem? > >> Or at least do a quick debug patch to confirm that indeed the window is "full" ? > > > > I'd be pretty surprised if the host bridge window actually full -- > > [mem 0x65400000-0xbfffffff] is a pretty big range and these devices > > only need 4K each. > > Yeah, I just checked and the highest used IOMEM window ends at > 0x811300ff leaving plenty of space after it for the 2 new windows. > > > But maybe we aren't smart enough when trying to allocate space. > > Places like __pci_bus_size_bridges() and __pci_assign_resource() > > are full of assumptions about what PCI BARs can go where, > > depending on 64bit-ness, prefetchability, etc. > > > > Maybe instrumenting those allocation paths would give some > > insight. Possibly we should go ahead and merge some permanent > > pci_dbg() stuff there too. > > I agree that this seems to be the most likely issue. I've build a > Fedora kernel pkg with some extra debugging added for the reporter > to be test. Since I'm reliant on a debug cycle where I provide a > kernel and then the reporter comes back with a new debug, and then > rince-repeat it might be a while before I get back to you on this. > Hopefully when I do get back I will have figured out what the > problem is. Thanks for the update. It's a real hassle to debug issues in this code, especially when it's a long repro cycle like this. I always wish we could feed the initial config (which I think we should already know from existing dmesg logging) into some kind of qemu test fixture so we could reproduce things locally. Bjorn
