[PATCH 10/10] PCI: Fix alignment calculation for resource size larger than align

Ilpo Järvinen
2026-03-24T17:01:00Z

The commit bc75c8e50711 ("PCI: Rewrite bridge window head alignment
function") did not use if (r_size <= align) check from pbus_size_mem()
for the new head alignment bookkeeping structure (aligns2[]). In some
configurations, this can result in producing a gap into the bridge
window which the resource larger than its alignment cannot fill.

The old alignment calculation algorithm was removed by the subsequent
commit 3958bf16e2fe ("PCI: Stop over-estimating bridge window size")
which renamed the aligns2[] array leaving only aligns[] array.

Add the if (r_size <= align) check back to avoid this problem.

Fixes: bc75c8e50711 ("PCI: Rewrite bridge window head alignment function")
Closes: https://lore.kernel.org/all/b05a6f14-979d-42c9-924c-d8408cb12ae7@roeck-us.net/
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
drivers/pci/setup-bus.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index edc0d682dcad..e5af8799c36f 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1333,7 +1333,14 @@ static void pbus_size_mem(struct pci_bus *bus, struct resource *b_res,
r_size = resource_size(r);
size += max(r_size, align);

- aligns[order] += align;
+ /*
+ * If resource's size is larger than its alignment,
+ * some configurations result in an unwanted gap in
+ * the head space that the larger resource cannot
+ * fill.
+ */
+ if (r_size <= align)
+ aligns[order] += align;
if (order > max_order)
max_order = order;
}
--
2.39.5