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Date: Thu, 19 Nov 2009 09:33:43 -0500
From: Vivek Goyal <vgoyal@redhat.com>
Subject: Re: Kdump issue with percpu_alloc=lpage
Message-ID: <20091119143343.GB8741@redhat.com>
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To: Tejun Heo <tj@kernel.org>
Cc: John Blackwood <john.blackwood@ccur.com>, "kexec@lists.infradead.org" <kexec@lists.infradead.org>

On Wed, Nov 18, 2009 at 06:25:14PM +0900, Tejun Heo wrote:
> Hello,
> 
> 10/29/2009 06:22 AM, John Blackwood wrote:
> >> Thanks Tejun. percpu_to_phys() makes sense to me also. John, would you
> >> like to post a patch for this.
> > 
> > Hi Vivek,
> > 
> > I'm probably not really NUMA/vm savy enough to attempt a patch
> > for approval at LKML.
> > 
> > But maybe someone else more qualified can take up the cause.
> 
> Is this still necessary for the current upstream where lpage allocator
> is gone (but vmalloc mapping is still there)?
> 

Hi Tejun,

I did load a kdump kernel on 32-rc7 and it worked fine. But I guess in
this case memory might have come from linearly mapped region.

If the default per cpu allocator can get memory from vmalloc region also, then
I think we will need this function which can map virtual address to
physical address.

Are there multiple allocators now? If yes, what are the command line
options and I can try to use some other allocator and see if I can force
the condition where memory comes from vmalloc region and I observe the
crash.

Once I can reproduce it, I can also send you the fix you suggested.

Thanks
Vivek

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