[PATCH 6.12.y 1/6] PCI: Use pbus_select_window() during BAR resize

[Sasha Levin <sashal@kernel.org>]

From: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

[ Upstream commit 7dc58aa7f1b32a215fb0b7c6ca30ddf4663dedf4 ]

Prior to a BAR resize, __resource_resize_store() loops through the normal
resources of the PCI device and releases those that match to the flags of
the BAR to be resized. This is necessary to allow resizing also the
upstream bridge window as only childless bridge windows can be resized.

While the flags check (mostly) works (if corner cases are ignored), the
more straightforward way is to check if the resources share the bridge
window. Change __resource_resize_store() to do the check using
pbus_select_window().

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20250829131113.36754-16-ilpo.jarvinen@linux.intel.com
Stable-dep-of: ee7471fe968d ("PCI: Skip Resizable BAR restore on read error")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/pci/pci-sysfs.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 122c182229b33d..a67de23a2cf94c 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1426,13 +1426,19 @@ static ssize_t __resource_resize_store(struct device *dev, int n,
 				       const char *buf, size_t count)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
-	unsigned long size, flags;
+	struct pci_bus *bus = pdev->bus;
+	struct resource *b_win, *res;
+	unsigned long size;
 	int ret, i;
 	u16 cmd;
 
 	if (kstrtoul(buf, 0, &size) < 0)
 		return -EINVAL;
 
+	b_win = pbus_select_window(bus, pci_resource_n(pdev, n));
+	if (!b_win)
+		return -EINVAL;
+
 	device_lock(dev);
 	if (dev->driver || pci_num_vf(pdev)) {
 		ret = -EBUSY;
@@ -1452,19 +1458,19 @@ static ssize_t __resource_resize_store(struct device *dev, int n,
 	pci_write_config_word(pdev, PCI_COMMAND,
 			      cmd & ~PCI_COMMAND_MEMORY);
 
-	flags = pci_resource_flags(pdev, n);
-
 	pci_remove_resource_files(pdev);
 
-	for (i = 0; i < PCI_BRIDGE_RESOURCES; i++) {
-		if (pci_resource_len(pdev, i) &&
-		    pci_resource_flags(pdev, i) == flags)
+	pci_dev_for_each_resource(pdev, res, i) {
+		if (i >= PCI_BRIDGE_RESOURCES)
+			break;
+
+		if (b_win == pbus_select_window(bus, res))
 			pci_release_resource(pdev, i);
 	}
 
 	ret = pci_resize_resource(pdev, n, size);
 
-	pci_assign_unassigned_bus_resources(pdev->bus);
+	pci_assign_unassigned_bus_resources(bus);
 
 	if (pci_create_resource_files(pdev))
 		pci_warn(pdev, "Failed to recreate resource files after BAR resizing\n");
-- 
2.53.0