[PATCH v8 3/6] PCI: Change extend_bridge_window() to set resource size directly

[PATCH v8 3/6] PCI: Change extend_bridge_window() to set resource size directly

[Nicholas Johnson]

Change extend_bridge_window() to set resource size directly instead of
using additional resource lists.

Because additional resource lists are optional resources, any algorithm
that requires guaranteed allocation that uses them cannot be guaranteed
to work.

Remove the resource from add_list. If it is set to zero size and left,
it can cause significant problems when it comes to assigning resources.

Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>
---
 drivers/pci/setup-bus.c | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 3b3055e0e..a072781ab 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1818,7 +1818,7 @@ static void extend_bridge_window(struct pci_dev *bridge, struct resource *res,
 				 struct list_head *add_list,
 				 resource_size_t new_size)
 {
-	struct pci_dev_resource *dev_res;
+	resource_size_t add_size;
 
 	if (res->parent)
 		return;
@@ -1826,17 +1826,10 @@ static void extend_bridge_window(struct pci_dev *bridge, struct resource *res,
 	if (resource_size(res) >= new_size)
 		return;
 
-	dev_res = res_to_dev_res(add_list, res);
-	if (!dev_res)
-		return;
-
-	/* Is there room to extend the window? */
-	if (new_size - resource_size(res) <= dev_res->add_size)
-		return;
-
-	dev_res->add_size = new_size - resource_size(res);
-	pci_dbg(bridge, "bridge window %pR extended by %pa\n", res,
-		&dev_res->add_size);
+	add_size = new_size - resource_size(res);
+	pci_dbg(bridge, "bridge window %pR extended by %pa\n", res, &add_size);
+	res->end = res->start + new_size - 1;
+	remove_from_list(add_list, res);
 }
 
 static void pci_bus_distribute_available_resources(struct pci_bus *bus,
-- 
2.22.0

Re: [PATCH v8 3/6] PCI: Change extend_bridge_window() to set resource size directly

[mika.westerberg]

On Fri, Jul 26, 2019 at 12:54:01PM +0000, Nicholas Johnson wrote:
> Change extend_bridge_window() to set resource size directly instead of
> using additional resource lists.
> 
> Because additional resource lists are optional resources, any algorithm
> that requires guaranteed allocation that uses them cannot be guaranteed
> to work.
> 
> Remove the resource from add_list. If it is set to zero size and left,
> it can cause significant problems when it comes to assigning resources.

It would be good if you would open bit more what kind of significant
problems this may result.

> Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>

Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>