linux-kernel - [PATCH] Disable Bus Master on PCI device shutdown

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Date:	Fri, 27 Apr 2012 13:00:33 -0600
From:	Khalid Aziz <khalid.aziz@...com>
To:	linux-kernel@...r.kernel.org
Cc:	bhelgaas@...gle.com, linux-pci@...r.kernel.org
Subject: [PATCH] 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@...com>
---
 drivers/pci/pci-driver.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 6b54b23..9db5940 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -420,6 +420,12 @@ static void pci_device_shutdown(struct device *dev)
 	pci_msi_shutdown(pci_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.
-- 
1.7.8.3

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