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Subject[PATCH v8 4/6] PCI: Allow extend_bridge_window() to shrink resource if necessary
Remove checks for resource size in extend_bridge_window(). This is
necessary to allow the pci_bus_distribute_available_resources() to
function when the kernel parameter pci=hpmemsize=nn[KMG] is used to
allocate resources. Because the kernel parameter sets the size of all
hotplug bridges to be the same, there are problems when nested hotplug
bridges are encountered. Fitting a downstream hotplug bridge with size X
and normal bridges with size Y into parent hotplug bridge with size X is
impossible, and hence the downstream hotplug bridge needs to shrink to
fit into its parent.

Add check for if bridge is extended or shrunken and adjust pci_dbg to
reflect this.

Reset the resource if its new size is zero (if we have run out of a
bridge window resource). If it is set to zero size and left, it can
cause significant problems when it comes to enabling devices.

Signed-off-by: Nicholas Johnson <>
drivers/pci/setup-bus.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index a072781ab..7e1dc892a 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1823,13 +1823,19 @@ static void extend_bridge_window(struct pci_dev *bridge, struct resource *res,
if (res->parent)

- if (resource_size(res) >= new_size)
- return;
- add_size = new_size - resource_size(res);
- pci_dbg(bridge, "bridge window %pR extended by %pa\n", res, &add_size);
+ if (new_size > resource_size(res)) {
+ add_size = new_size - resource_size(res);
+ pci_dbg(bridge, "bridge window %pR extended by %pa\n", res,
+ &add_size);
+ } else if (new_size < resource_size(res)) {
+ add_size = resource_size(res) - new_size;
+ pci_dbg(bridge, "bridge window %pR shrunken by %pa\n", res,
+ &add_size);
+ }
res->end = res->start + new_size - 1;
remove_from_list(add_list, res);
+ if (!new_size)
+ reset_resource(res);

static void pci_bus_distribute_available_resources(struct pci_bus *bus,
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