linux-kernel - Re: kdump broken on 2.6.37-rc4

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Date:	Fri, 17 Dec 2010 12:01:47 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Yinghai <yinghai@...nel.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Stanislaw Gruszka <sgruszka@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Maxim Uvarov <muvarov@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Neil Horman <nhorman@...hat.com>
Subject: Re: kdump broken on 2.6.37-rc4

On Thu, Dec 16, 2010 at 07:58:48PM -0800, Yinghai wrote:
> Please don't do that to 64 bit
> 
> My big system with 1024g memory and a lot of cards with rhel 6 to make kdump work must have crashkernel=512m and second kernel need to take pci=nomsi
> 

I agree here that we should not do it for 64 bit.

- Just because we need it for 32 bit does not mean we should limit it for
  64bit. And we do want to have the capability to boot the kernel from as
  high memory as possible so creating another aritificial limit is counter
  to that.

- I would not worry too much about backward compatibility and allow
  booting 32bit kernel till 768MB. The reason being that most of the
  distros use same kernel for crash dumping as regular kernel. Maintainig
  two separate kernels is big hassle.

  So a small set of people who run into issue, would need to change kernel
  command line "crashkernel=128M@64M" or something similar.

Thanks
Vivek 

> Thanks
> 
> On Dec 16, 2010, at 7:31 PM, "H. Peter Anvin" <hpa@...or.com> wrote:
> 
> > On 12/15/2010 08:29 PM, Yinghai Lu wrote:
> >> please check
> >> 
> >> [PATCH] x86, crashkernel, 32bit: only try to get range under 512M
> >> 
> >> Steanishlaw report kdump is 32bit is broken.
> >> 
> >> in misc.c for decompresser, it will do sanity checking to make sure heap
> >> heap under 512M.
> >> 
> >> So limit it in first kernel under 512M for 32bit system.
> >> 
> >> Reported-by: Stanislaw Gruszka <sgruszka@...hat.com>
> >> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> >> 
> >> ---
> >> arch/x86/kernel/setup.c |   14 +++++++++++++-
> >> 1 file changed, 13 insertions(+), 1 deletion(-)
> >> 
> > 
> > I'd like to apply a modified version of this patch (attached.)
> > 
> > Ack/nak, people?
> > 
> >    -hpa
> > <0001-x86-kexec-Limit-the-crashkernel-address-to-512-MiB.patch>
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