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: <1162588660.19677.118.camel@ustr-linux-shaha1.unisys.com>
Date:	Fri, 03 Nov 2006 16:17:39 -0500
From:	Amul Shah <amul.shah@...sys.com>
To:	Andi Kleen <ak@...e.de>
Cc:	vgoyal@...ibm.com, LKML <linux-kernel@...r.kernel.org>,
	Fastboot mailing list <fastboot@...ts.osdl.org>
Subject: Re: [RFC] [PATCH 2.6.19-rc4] kdump panics early in boot when   
	reserving MP Tables located in high memory

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).

> > 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?

Amul

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