Re: [PATCH v2 2/3] PCI: Fix pdev_resources_assignable() disparity

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Jun 30, 2025 at 05:26:40PM +0300, Ilpo Järvinen wrote:
> pdev_sort_resources() uses pdev_resources_assignable() helper to decide
> if device's resources cannot be assigned. pbus_size_mem(), on the other
> hand, does not do the same check. This could lead into a situation
> where a resource ends up on realloc_head list but is not on the head
> list, which is turn prevents emptying the resource from the
> realloc_head list in __assign_resources_sorted().
> 
> A non-empty realloc_head is unacceptable because it triggers an
> internal sanity check as show in this log with a device that has class
> 0 (PCI_CLASS_NOT_DEFINED):

Is the class relevant here?

> pci 0001:01:00.0: [144d:a5a5] type 00 class 0x000000 PCIe Endpoint
> pci 0001:01:00.0: BAR 0 [mem 0x00000000-0x000fffff 64bit]
> pci 0001:01:00.0: ROM [mem 0x00000000-0x0000ffff pref]
> pci 0001:01:00.0: enabling Extended Tags
> pci 0001:01:00.0: PME# supported from D0 D3hot D3cold
> pci 0001:01:00.0: 15.752 Gb/s available PCIe bandwidth, limited by 8.0 GT/s PCIe x2 link at 0001:00:00.0 (capable of 31.506 Gb/s with 16.0 GT/s PCIe x2 link)
> pcieport 0001:00:00.0: bridge window [mem 0x00100000-0x001fffff] to [bus 01-ff] add_size 100000 add_align 100000
> pcieport 0001:00:00.0: bridge window [mem 0x40000000-0x401fffff]: assigned
> ------------[ cut here ]------------
> kernel BUG at drivers/pci/setup-bus.c:2532!
> Internal error: Oops - BUG: 00000000f2000800 [#1]  SMP
> ...
> Call trace:
>  pci_assign_unassigned_bus_resources+0x110/0x114 (P)
>  pci_rescan_bus+0x28/0x48
> 
> Use pdev_resources_assignable() also within pbus_size_mem() to skip
> processing of non-assignable resources which removes the disparity in
> between what resources pdev_sort_resources() and pbus_size_mem()
> consider. As non-assignable resources are no longer processed, they are
> not added to the realloc_head list, thus the sanity check no longer
> triggers.
> 
> This disparity problem is very old but only now became apparent after
> the commit 2499f5348431 ("PCI: Rework optional resource handling") that
> made the ROM resources optional when calculating bridge window sizes
> which required adding the resource to the realloc_head list.
> Previously, bridge windows were just sized larger than necessary.
> 
> Fixes: 2499f5348431 ("PCI: Rework optional resource handling")
> Reported-by: Tudor Ambarus <tudor.ambarus@linaro.org>

Any URL we can include here for the report?

> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> Cc: <stable@vger.kernel.org>
> ---
>  drivers/pci/setup-bus.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index f90d49cd07da..24863d8d0053 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -1191,6 +1191,7 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
>  			resource_size_t r_size;
>  
>  			if (r->parent || (r->flags & IORESOURCE_PCI_FIXED) ||
> +			    !pdev_resources_assignable(dev) ||
>  			    ((r->flags & mask) != type &&
>  			     (r->flags & mask) != type2 &&
>  			     (r->flags & mask) != type3))
> -- 
> 2.39.5
>