Re: [PATCH 1/1] PCI: Do not size non-existing prefetchable window

[Ilpo Järvinen]

On Mon, 27 Oct 2025, Bjorn Helgaas wrote:

> On Mon, Oct 27, 2025 at 03:24:23PM +0200, Ilpo Järvinen wrote:
> > pbus_size_mem() should only be called for bridge windows that exist but
> > __pci_bus_size_bridges() may point 'pref' to a resource that does not
> > exist (has zero flags) in case of non-root buses.
> > 
> > When prefetchable bridge window does not exist, the same
> > non-prefetchable bridge window is sized more than once which may result
> > in duplicating entries into the realloc_head list. Duplicated entries
> > are shown in this log and trigger a WARN_ON() because realloc_head had
> > residual entries after the resource assignment algorithm:
> > 
> > pci 0000:00:03.0: [11ab:6820] type 01 class 0x060400 PCIe Root Port
> > pci 0000:00:03.0: PCI bridge to [bus 00]
> > pci 0000:00:03.0:   bridge window [io  0x0000-0x0fff]
> > pci 0000:00:03.0:   bridge window [mem 0x00000000-0x000fffff]
> > pci 0000:00:03.0: bridge window [mem 0x00200000-0x003fffff] to [bus 02] add_size 200000 add_align 200000
> > pci 0000:00:03.0: bridge window [mem 0x00200000-0x003fffff] to [bus 02] add_size 200000 add_align 200000
> > pci 0000:00:03.0: bridge window [mem 0xe0000000-0xe03fffff]: assigned
> > pci 0000:00:03.0: PCI bridge to [bus 02]
> > pci 0000:00:03.0:   bridge window [mem 0xe0000000-0xe03fffff]
> > ------------[ cut here ]------------
> > WARNING: CPU: 0 PID: 1 at drivers/pci/setup-bus.c:2373 pci_assign_unassigned_root_bus_resources+0x1bc/0x234
> > 
> > Check resource flags of 'pref' and only size the prefetchable window if
> > the resource has the IORESOURCE_PREFETCH flag.
> > 
> > Fixes: ae88d0b9c57f ("PCI: Use pbus_select_window_for_type() during mem window sizing")
> > Link: https://lore.kernel.org/linux-pci/51e8cf1c62b8318882257d6b5a9de7fdaaecc343.camel@xxxxxxxxx/
> > Reported-by: Klaus Kudielka <klaus.kudielka@xxxxxxxxx>
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> 
> Since ae88d0b9c57f appeared in v6.18-rc1, this looks like v6.18
> material, right?
>
> Applied to pci/for-linus for v6.18 on that assumption, thanks!

Yes, it's for-linus material.

-- 
 i.

> >  drivers/pci/setup-bus.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> > index 362ad108794d..7cb6071cff7a 100644
> > --- a/drivers/pci/setup-bus.c
> > +++ b/drivers/pci/setup-bus.c
> > @@ -1604,7 +1604,7 @@ void __pci_bus_size_bridges(struct pci_bus *bus, struct list_head *realloc_head)
> >  		pbus_size_io(bus, realloc_head ? 0 : additional_io_size,
> >  			     additional_io_size, realloc_head);
> >  
> > -		if (pref) {
> > +		if (pref && (pref->flags & IORESOURCE_PREFETCH)) {
> >  			pbus_size_mem(bus,
> >  				      IORESOURCE_MEM | IORESOURCE_PREFETCH |
> >  				      (pref->flags & IORESOURCE_MEM_64),
> > 
> > base-commit: 2f2c7254931f41b5736e3ba12aaa9ac1bbeeeb92
> > -- 
> > 2.39.5
> > 
>