Re: [PATCH] PCI: Clear Bus Master bit only on kexec reboot

[Khalid Aziz]

On 11/27/2013 03:07 PM, Matthew Garrett wrote:
> On Wed, Nov 27, 2013 at 02:01:06PM -0800, Greg KH wrote:
> > Anyway, I really don't care either way, but this seems like something
> > that the drivers should be doing.  What suddenly changed that caused
> > this problem to occur that hasn't happened in the years prior to now
> > that drives this to be a stable-kernel issue?
>
> We started clearing the busmaster bit on all devices on shutdown in
> 3.something in order to ensure that DMA wasn't occuring while we were
> in the process of performing a kexec. Some machines freeze on shutdown
> as a result. This patch reverts back to the original behaviour on real
> shutdown, while still avoiding the "This PCI device scribbled over my
> new kernel" kexec case.

Thanks for explaining this, Matthew. That was my reasoning exactly for 
why this patch should apply to stable. It fixes a real problem some 
users are experiencing. Commit log contains the URL to bugzilla entry 
for the problem.

--
Khalid
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