[PATCH] PCI: Only restore state that was successfully saved around a reset

[lirongqing <lirongqing@baidu.com>]

From: Li RongQing <lirongqing@baidu.com>

pci_dev_save_and_disable() returns early when config space is inaccessible,
without saving anything, but pci_dev_restore() calls pci_restore_state()
unconditionally and pci_restore_state() does not look at state_saved. After
the reset makes config space accessible again, the all-zero or stale
saved_config_space[] array is written back to the device, clearing Command,
BARs and, for bridges, the bus number registers.

Clear state_saved when the save is skipped and only restore when a state
was saved.

Fixes: e18d1abc3bff ("PCI: Avoid saving config space state if inaccessible")
Signed-off-by: Li RongQing <lirongqing@baidu.com>
---
 drivers/pci/pci.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 67fe565..ddb86dd 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5156,8 +5156,10 @@ static void pci_dev_save_and_disable(struct pci_dev *dev)
 	 */
 	pci_set_power_state(dev, PCI_D0);
 
-	if (!pci_dev_config_accessible(dev, "save state"))
+	if (!pci_dev_config_accessible(dev, "save state")) {
+		dev->state_saved = false;
 		return;
+	}
 
 	pci_save_state(dev);
 	/*
@@ -5175,7 +5177,8 @@ static void pci_dev_restore(struct pci_dev *dev)
 	const struct pci_error_handlers *err_handler =
 			dev->driver ? dev->driver->err_handler : NULL;
 
-	pci_restore_state(dev);
+	if (dev->state_saved)
+		pci_restore_state(dev);
 
 	/*
 	 * dev->driver->err_handler->reset_done() is protected against
-- 
2.9.4