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

Ilpo Järvinen
2023-12-22T12:29:28Z

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@linux.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