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

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Message-Id: <20251027132423.8841-1-ilpo.jarvinen@linux.intel.com>
Date: Mon, 27 Oct 2025 15:24:23 +0200
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Klaus Kudielka <klaus.kudielka@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/1] PCI: Do not size non-existing prefetchable window

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@gmail.com/
Reported-by: Klaus Kudielka <klaus.kudielka@...il.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
---
 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