linux-kernel - Re: [RFC] [PATCH 2.6.19-rc4] kdump panics early in boot when reserving MP Tables located in high memory

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Message-Id: <200611032301.32094.ak@suse.de>
Date:	Fri, 3 Nov 2006 23:01:31 +0100
From:	Andi Kleen <ak@...e.de>
To:	Amul Shah <amul.shah@...sys.com>
Cc:	vgoyal@...ibm.com, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] [PATCH 2.6.19-rc4] kdump panics early in boot when    reserving MP Tables located in high memory

On Friday 03 November 2006 22:17, Amul Shah wrote:
> On Fri, 2006-11-03 at 20:52 +0100, Andi Kleen wrote:
> > On Friday 03 November 2006 20:47, Amul Shah wrote:
> > 
> > > Andi, Vivek is right.  We can use end_pfn_map.  My observation is wrong.
> > 
> > Ok. Then my patch should work?
> 
> The patch does work on a 2.6.16 derived kernel (SLES 10 kernel).  The
> 2.6.19-rc4 kernel is doing some funny things when I use it as a kdump
> kernel (regardless of the patch).

Magnus had another patch for that which I applied

ftp://ftp.firstfloor.org/pub/ak/x86_64/quilt/patches/setup-saved_max_pfn-correctly-kdump

Does it work with that?

 
> > > Vivek, the problem condition is in generic reserve_bootmem_core
> > > (mm/bootmem.c), where this
> > > 	BUG_ON(PFN_DOWN(addr) >= bdata->node_low_pfn);
> > > checks the target address against the top of that node's memory.
> > 
> > In general these early BUGs should be eliminated - they are always
> > messy because the kernel exception handlers are not fully functional
> > yet. printks or worst case panics are better.
> > 
> > -Andi
> 
> I assume that we are not going to change mm/bootmem.c since your patch
> works.  Am I right?

Yep.

-Andi
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