From: Mahesh J Salgaonkar <mahesh@linux.vnet.ibm.com>
To: "Américo Wang" <xiyou.wangcong@gmail.com>
Cc: kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
linuxppc-dev@ozlabs.org,
"Eric W. Biederman" <ebiederm@xmission.com>,
akpm@linux-foundation.org, Anton Blanchard <anton@samba.org>
Subject: Re: [PATCH 1/2] kdump: Allow shrinking of kdump region to be overridden
Date: Mon, 14 Mar 2011 23:43:15 +0530 [thread overview]
Message-ID: <20110314181315.GA16075@in.ibm.com> (raw)
In-Reply-To: <20110309142108.GD16951@cr0.redhat.com>
On Wed, Mar 09, 2011 at 10:21:08PM +0800, Américo Wang wrote:
> On Wed, Mar 09, 2011 at 11:46:57PM +1100, Anton Blanchard wrote:
> >
> >Hi,
> >
> >> The crashkernel region is specified via kernel cmdline, so why
> >> not just drop a failure when it overlaps with RMO region?
> >> Am I missing something?
> >
> >Unfortunately a ppc64 kernel requires a chunk of RMO memory. We would
> >need the ability to specify multiple crashkernel regions - about 32MB
> >in the RMO and the rest can be anywhere. That sounds pretty fragile for
> >a user to configure successfully on the cmdline.
> >
> >Thats why the ppc64 crashkernel region begins mid way through the RMO
> >region. It means both kernels get a chunk of RMO and we only have to
> >deal with one crashkernel reservation in all the tools and
> >documentation.
> >
>
> So, when I specify 128M in cmdline, 32M of them are RMO, and the
> rest 96M are normal memory? And when I want to free all of them,
> actually the 32M RMO will never be freed?
In ppc64 implementation the crashkernel region begins mid way through
the RMO and spans across into the normal memory. For e.g. on power system
with 128M RMO size, when user specifies 128M in cmdline, the crashkernel
starts from default offset 64M through 192M. Which means 64M in RMO region
and rest beyond RMO.
<-------------------RMO--------------->
<---rtas-->
0 64M 128M End
|=====================|=================|===========|============|
Crash_start|<------------128M----------->| Crash End
During free we do free all of them including RMO region. But since the rtas
region is always on top of RMO, crashkernel memory overlaps rtas region and
we endup freeing that even, which is causing the crash.
>
>
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> http://lists.infradead.org/mailman/listinfo/kexec
--
Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
next prev parent reply other threads:[~2011-03-14 18:13 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-25 0:22 [PATCH 1/2] kdump: Allow shrinking of kdump region to be overridden Anton Blanchard
2010-08-25 0:23 ` [PATCH 2/2] powerpc: kdump: Override crash_free_reserved_phys_range to avoid freeing RTAS Anton Blanchard
2010-08-25 0:37 ` [PATCH 1/2] kdump: Allow shrinking of kdump region to be overridden Eric W. Biederman
2011-03-09 6:32 ` Mahesh Jagannath Salgaonkar
2011-03-09 12:20 ` Américo Wang
2011-03-09 12:46 ` Anton Blanchard
2011-03-09 14:21 ` Américo Wang
2011-03-14 18:13 ` Mahesh J Salgaonkar [this message]
2011-03-15 7:52 ` Américo Wang
2011-03-15 16:52 ` Mahesh J Salgaonkar
2011-03-21 3:10 ` WANG Cong
2011-03-24 4:33 ` Benjamin Herrenschmidt
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