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

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Date:	Thu, 07 Jun 2012 11:36:53 -0600
From:	Khalid Aziz <khalid.aziz@...com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Matthew Garrett <mjg@...hat.com>, linux-kernel@...r.kernel.org,
	bhelgaas@...gle.com, linux-pci@...r.kernel.org
Subject: Re: [PATCH] Disable Bus Master on PCI device shutdown

On Thu, 2012-06-07 at 10:07 -0700, Andi Kleen wrote:
> Alan Cox <alan@...rguk.ukuu.org.uk> writes:
> 
> >> This protects against the case where a piece of hardware is continuing 
> >> to DMA even after the driver shutdown method has been called? I'm not 
> >
> > It doesn't. We also have hardware which craps itself if you clear the bus
> > mastering bit and we have platforms where the BIOS gets most upset if you
> > do that on suspend paths. There are also lots of devices that simply
> > ignore the bus mastering bit !
> 
> But it also makes my system do kexec successfully for the first time.
> 
> Maybe can make it an option.
> 
> n-Andi
> 

Hi Andi,

That makes my day :) It will be very helpful to see which PCI devices
your system has.

I was thinking about kernel command line option this morning and had
started looking at reset_devices option to see if I could leverage that
one in any way.

-- 
====================================================================
Khalid Aziz                                         Unix Systems Lab
(970)898-9214                                        Hewlett-Packard
khalid.aziz@...com                                  Fort Collins, CO

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