lkml.org 
[lkml]   [2013]   [Jan]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH 4/5] PCI: don't touch enable_cnt in pci_device_shutdown()
On 01/18/2013 06:42 AM, Konstantin Khlebnikov wrote:
> comment in commit b566a22c23327f18ce941ffad0ca907e50a53d41
> ("PCI: disable Bus Master on PCI device shutdown") says:
>
> | 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.
>
> Seems like pci_clear_master() must be used here instead of pci_disable_device(),
> because it disables Bus Muster unconditionally and doesn't changes enable_cnt.
>
> Signed-off-by: Konstantin Khlebnikov<khlebnikov@openvz.org>
> Cc: linux-pci@vger.kernel.org
> Cc: Bjorn Helgaas<bhelgaas@google.com>
> Cc: Khalid Aziz<khalid.aziz@hp.com>

Hmmm.... wondering if this was the problem why kexec folks
said that device_shutdown() didn't work on all systems (when
trying to stop DMA, esp. on IOMMU-enabled systems...).

Bjorn: do you have a list &/or contact in kexec space to try this
patch vs the "reset every PCI bus" strategy that is currently
being pushed for kexec's method to halt DMA from a PCI device ?

> ---
> drivers/pci/pci-driver.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index 030dbf0..853d605 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -392,7 +392,7 @@ static void pci_device_shutdown(struct device *dev)
> * Turn off Bus Master bit on the device to tell it to not
> * continue to do DMA
> */
> - pci_disable_device(pci_dev);
> + pci_clear_master(pci_dev);
> }
>
> #ifdef CONFIG_PM
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-pci" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html



\
 
 \ /
  Last update: 2013-01-18 19:21    [W:0.138 / U:0.144 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site