linux-kernel - [PATCH v2 1/7] PCI: Fix resource double counting on remove & rescan

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Date: Thu, 28 Dec 2023 18:57:01 +0200
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: linux-pci@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Igor Mammedov <imammedo@...hat.com>,
	Lukas Wunner <lukas@...ner.de>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Andy Shevchenko <andriy.shevchenko@...el.com>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Yinghai Lu <yinghai@...nel.org>,
	linux-kernel@...r.kernel.org
Cc: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: [PATCH v2 1/7] PCI: Fix resource double counting on remove & rescan

pbus_size_mem() keeps the size of the optional resources in
children_add_size. When calculating the PCI bridge window size,
calculate_memsize() lower bounds size by old_size before adding
children_add_size and performing the window size alignment. This
results in double counting for the resources in children_add_size
because old_size may be based on the previous size of the bridge
window after it has already included children_add_size (that is,
size1 in pbus_size_mem() from an earlier invocation of that
function).

As a result, on repeated remove of the bus & rescan cycles the resource
size keeps increasing when children_add_size is non-zero as can be seen
from this extract:

iomem0:  23fffd00000-23fffdfffff : PCI Bus 0000:03
iomem1:  20000000000-200001fffff : PCI Bus 0000:03
iomem2:  20000000000-200002fffff : PCI Bus 0000:03
iomem3:  20000000000-200003fffff : PCI Bus 0000:03
iomem4:  20000000000-200004fffff : PCI Bus 0000:03

Solve the double counting by moving old_size check later in
calculate_memsize() so that children_add_size is already accounted for.

After the patch, the bridge window retains its size as expected:

iomem0:  23fffd00000-23fffdfffff : PCI Bus 0000:03
iomem1:  20000000000-200000fffff : PCI Bus 0000:03
iomem2:  20000000000-200000fffff : PCI Bus 0000:03

Fixes: a4ac9fea016f ("PCI : Calculate right add_size")
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
---
 drivers/pci/setup-bus.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index fd74f1c99dba..e3e6ff8854a7 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -820,11 +820,9 @@ static resource_size_t calculate_memsize(resource_size_t size,
 		size = min_size;
 	if (old_size == 1)
 		old_size = 0;
-	if (size < old_size)
-		size = old_size;
 
-	size = ALIGN(max(size, add_size) + children_add_size, align);
-	return size;
+	size = max(size, add_size) + children_add_size;
+	return ALIGN(max(size, old_size), align);
 }
 
 resource_size_t __weak pcibios_window_alignment(struct pci_bus *bus,
-- 
2.30.2