On Tue, Mar 31, 2026 at 05:01:49PM -0600, Alex Williamson wrote: > On Tue, 31 Mar 2026 15:09:34 +0200 Lukas Wunner <[email protected]> wrote: > > On Mon, Mar 30, 2026 at 08:14:53AM +0200, Bernd Schumacher wrote: > > > [ 0.318903] pci 0000:07:00.0: [dd01:0003] type 00 class 0x048000 PCIe > > > Endpoint > > > [ 0.318939] pci 0000:07:00.0: BAR 0 [mem > > > 0xfffffffffc500000-0xfffffffffc50ffff 64bit] > > > > BIOS initially sets the BAR address to an incorrect value (the top 32 bits > > should be all zeroes instead of all ones)... > > > > > [ 0.339685] pci 0000:07:00.0: BAR 0 [mem > > > 0xfffffffffc500000-0xfffffffffc50ffff 64bit]: can't claim; no compatible > > > bridge window > > [...] > > > [ 0.311065] pci 0000:02:03.0: [1022:57a3] type 01 class 0x060400 PCIe > > > Switch Downstream Port > > > [ 0.311107] pci 0000:02:03.0: PCI bridge to [bus 07] > > > [ 0.311118] pci 0000:02:03.0: bridge window [mem > > > 0xfc500000-0xfc5fffff] > > > > ... this doesn't fit into the window of the bridge above the DVB card, > > which has the top 32 bits set to all zeroes... > > > > > [ 0.357346] pci 0000:07:00.0: BAR 0 [mem 0xfc500000-0xfc50ffff 64bit]: > > > assigned > > > > ... the kernel fixes the incorrect BAR, but it seems there's an ordering > > issue such that pci_save_state() is called beforehand. It's weird that > > this doen't occur with newer kernels and it would be good to understand why. > > I'm not seeing the ordering issue despite staring at the code for a while. > > Do we know this isn't occurring on newer kernels?
Yes, the reporter tested 6.19.8 and the issue does not occur there: https://bugs.debian.org/1131025 > AIUI, we're saving the state via the call chain invoked by > subsys_initcall(pcibios_init), but I think we're doing the resource > fixes in fs_initcall(pcibios_assign_resources). That suggests that > the saved state would have the bogus BAR values. Hm, seems like a valid observation. But a call to pci_bus_add_devices() is generally preceded by a call to pci_assign_unassigned_root_bus_resources(), see e.g. pci_host_probe() or acpi_pci_root_add(). The latter is what's usually used on x86, whereas pcibios_init() (actually I think you meant pci_subsys_init()) is for legacy PCI initialization on x86. Perhaps you're right and the correction of the BAR value happens in the fs_initcall. We should be able to confirm that once the reporter has tested the debug patch I provided, which inserts a dump_stack() in the BAR correction codepath as well as in pci_save_state(). > If we toss PM runtime into that mix, pci_pm_default_resume_early() will > call pci_restore_state() however pci_save_state() in that file is > mostly wrapped around pci_dev->state_saved guards. The state_saved guards only serve the purpose of recognizing whether the driver called pci_save_state() on suspend. If it did not, the PCI core calls pci_save_state(). Thanks for taking a look! Lukas
