PCI: disable Bus Master on PCI device shutdown

Disable Bus Master bit on the device in pci_device_shutdown() to ensure PCI
devices do not continue to DMA data after shutdown.  This can cause memory
corruption in case of a kexec where the current kernel shuts down and
transfers control to a new kernel while a PCI device continues to DMA to
memory that does not belong to it any more in the new kernel.

I have tested this code on two laptops, two workstations and a 16-socket
server.  kexec worked correctly on all of them.

Signed-off-by: Khalid Aziz <khalid.aziz@hp.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 6b54b23..bf0cee6 100644 (file)
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -421,6 +421,12 @@ static void pci_device_shutdown(struct device *dev)
        pci_msix_shutdown(pci_dev);
 
        /*
+        * Turn off Bus Master bit on the device to tell it to not
+        * continue to do DMA
+        */
+       pci_disable_device(pci_dev);
+
+       /*
         * Devices may be enabled to wake up by runtime PM, but they need not
         * be supposed to wake up the system from its "power off" state (e.g.
         * ACPI S5).  Therefore disable wakeup for all devices that aren't