Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753940Ab3CRPeE (ORCPT ); Mon, 18 Mar 2013 11:34:04 -0400 Received: from mx1.redhat.com ([209.132.183.28]:5549 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753344Ab3CRPeC (ORCPT ); Mon, 18 Mar 2013 11:34:02 -0400 Date: Mon, 18 Mar 2013 11:33:48 -0400 From: Vivek Goyal To: Yinghai Lu Cc: "Eric W. Biederman" , "H. Peter Anvin" , Konrad Rzeszutek Wilk , Thomas Gleixner , Ingo Molnar , WANG Chao , linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86, kdump: Set crashkernel_low automatically Message-ID: <20130318153348.GA25806@redhat.com> References: <20130311182655.GB12107@redhat.com> <513E2695.3080707@zytor.com> <513E28B8.3000502@zytor.com> <20130311191031.GD12107@redhat.com> <20130311193824.GA14738@redhat.com> <20130318144603.GA20743@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130318144603.GA20743@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1843 Lines: 41 On Mon, Mar 18, 2013 at 10:46:03AM -0400, Vivek Goyal wrote: > On Mon, Mar 11, 2013 at 12:44:15PM -0700, Yinghai Lu wrote: > > On Mon, Mar 11, 2013 at 12:39 PM, Yinghai Lu wrote: > > > On Mon, Mar 11, 2013 at 12:38 PM, Vivek Goyal wrote: > > >>> No need to use crashkernel_high, we can just cashkernel=X@Y instead. > > >> > > >> crashkernel=X@Y is little different. It assumes user knows the memory > > >> map and location "Y" is fixed. There might not be any memory at "Y". > > > > > > then use crashkernel=4G? > > > > I re attached -v2 and -v3. > > > > I'm ok that any one is applied or two get applied all together. > > > > only affect 64bit > > -v2: try under under 896M, then 4G, then MAXMEM > > -v3: auto set crashkernel_low with swiotlb size. > > So, what's the resolution on this issue. Is the verdict that we always > reserve high. Update your kexec-tools to cope with that. For swiotlb > issue, modify kexec-tools to copy low memory in backup region and give > low memory to second kernel for software iotlb? > > I am assuming that updating tools will not help with loading and using > of 32bit bzImage. So user needs to use crashkernel=X@Y syntax to cope > with that? (Given the fact that copying code around after crash carries > the greater risk of ongoing DMA on destination location). Thinking more about it, if ongoing DMA is an issue, then setting up software iotlb in those areas is also prone to being overwritten by those DMAs. Hence, reserving memory low where no DMA is setup by first kernel, seems somewhat safer. Thanks Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/