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

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Message-ID: <CAErSpo7LEDFq6=6vzBg+1eT-v+Y+oEm=AoUo2hiJ4-i3NafPYw@mail.gmail.com>
Date:	Fri, 4 May 2012 11:15:58 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	linux-pci@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Disable Bus Master on PCI device shutdown

On Thu, May 3, 2012 at 5:52 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> On Fri, Apr 27, 2012 at 1:00 PM, Khalid Aziz <khalid.aziz@...com> wrote:
>> 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.
>
> Any comment on this, Eric?  It seems reasonable to me.

Applied to my "next" branch, thanks.

Bjorn
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