From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp01.au.ibm.com (e23smtp01.au.ibm.com [202.81.31.143]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e23smtp01.au.ibm.com", Issuer "Equifax" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id C9CF21007D3 for ; Fri, 27 Nov 2009 19:35:50 +1100 (EST) Received: from d23relay05.au.ibm.com (d23relay05.au.ibm.com [202.81.31.247]) by e23smtp01.au.ibm.com (8.14.3/8.13.1) with ESMTP id nAR8YC2m022413 for ; Fri, 27 Nov 2009 19:34:12 +1100 Received: from d23av03.au.ibm.com (d23av03.au.ibm.com [9.190.234.97]) by d23relay05.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id nAR8WGq41540266 for ; Fri, 27 Nov 2009 19:32:16 +1100 Received: from d23av03.au.ibm.com (loopback [127.0.0.1]) by d23av03.au.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id nAR8Zn27015498 for ; Fri, 27 Nov 2009 19:35:49 +1100 Message-ID: <4B0F8F62.3050000@in.ibm.com> Date: Fri, 27 Nov 2009 14:05:46 +0530 From: "M. Mohan Kumar" MIME-Version: 1.0 To: Bernhard Walle Subject: Re: [PATCH] Reserve memory for kdump kernel within RMO region References: <20091125131747.GA28857@in.ibm.com> <4B0D7CF4.8040402@bwalle.de> <4B0E628A.9070009@in.ibm.com> <4B0ED674.6050501@bwalle.de> In-Reply-To: <4B0ED674.6050501@bwalle.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: kexec@lists.infradead.org, ppcdev List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 11/27/2009 12:56 AM, Bernhard Walle wrote: > M. Mohan Kumar schrieb: >> On 11/26/2009 12:22 AM, Bernhard Walle wrote: >>> M. Mohan Kumar schrieb: >>>> Reserve memory for kdump kernel within RMO region >>>> >>>> When the kernel size exceeds 32MB(observed with some distros), memory >>>> for kdump kernel can not be reserved as kdump kernel base is assumed to >>>> be 32MB always. When the kernel has CONFIG_RELOCATABLE option enabled, >>>> provide the feature to reserve the memory for kdump kernel anywhere in >>>> the RMO region. >> >> Hi Bernhard, >> >>> Correct me if I'm wrong, but: CONFIG_RELOCATABLE is for the kernel that >>> gets loaded as crashkernel, not for the kernel that loads the >>> crashkernel. So it would be perfectly fine that a kernel that has not >>> CONFIG_RELOCATABLE set would load another kernel that has >>> CONFIG_RELOCATABLE set on an address != 32 M. >> >> No, with relocatable option, the same kernel is used as both production >> and kdump kernel. > > Can be, but it's not strictly necessary. It depends what userland does. > Especially it's possible that a non-relocatable, self-compiled kernel > loads a relocatable distribution kernel as capture kernel. > I don't understand why a non-relocatable kernel will use relocatable kernel for capturing kdump kernel. The idea for relocatable kernel is to avoid using two different kernels to capture kernel dump. > Also, it would make sense to make the behaviour symmetric across > platforms. Currently we have: > > - x86 and ia64: Without offset on command line, use any offset > With offset on command line, use that offset and fail > if no memory is available at that offset. > - ppc64: Always use 32M and ignore the offset. > > If your patch gets applied, we have: > > - ppc64: With CONFIG_RELOCATABLE, use any offset > With offset on command > > I don't see why the behaviour on ppc64 should be completely different. > > Having maintained kdump for SUSE for x86, ia64 and partly ppc64 in the > past, I always felt that ppc64 is more different from x86 than ia64 is > from x86. That's one more step into that direction without a technical > reason. Also with the crashkernel=auto parameter (patches are not yet merged), the crashkernel base (offset) by default would be 32MB. In this case if a kernel passed with crashkernel=auto and if the first kernel size exceeds 32MB, memory for kdump kernel will always fail. > > Having that all said: If your patch gets in mainline kernel, than we > should change the behaviour also for x86 and ia64. > > > > Regards, > Bernhard