Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754388Ab3CKUCG (ORCPT ); Mon, 11 Mar 2013 16:02:06 -0400 Received: from terminus.zytor.com ([198.137.202.10]:45574 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750948Ab3CKUCE (ORCPT ); Mon, 11 Mar 2013 16:02:04 -0400 Message-ID: <513E37B0.6090709@zytor.com> Date: Mon, 11 Mar 2013 12:59:44 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130219 Thunderbird/17.0.3 MIME-Version: 1.0 To: Vivek Goyal CC: "Eric W. Biederman" , Yinghai Lu , Thomas Gleixner , Ingo Molnar , WANG Chao , linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86, kdump: Set crashkernel_low automatically References: <513D52BA.3070206@redhat.com> <1362977817-23297-1-git-send-email-yinghai@kernel.org> <20130311144853.GB8482@redhat.com> <20130311150256.GC8482@redhat.com> <20130311182655.GB12107@redhat.com> <513E2695.3080707@zytor.com> <513E28B8.3000502@zytor.com> <87r4jllpfb.fsf@xmission.com> <20130311192247.GG12107@redhat.com> In-Reply-To: <20130311192247.GG12107@redhat.com> X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 942 Lines: 21 On 03/11/2013 12:22 PM, Vivek Goyal wrote: > > So always reserving memory at highest address will break all the cases > which work without iommu and rely on swiotlb. I think first we need > to make sure that kdump works reliably with iommu on, and then try > to move to always reserving memory at higest possible address. > We should clearly always reserve an swiotlb window, *or*, probably much better, teach the kdump kernel to *make* an swiotlb window (by having a memory buffer in its reserved memory area into which it copies a chunk of low memory, just as we do for the bottom megabyte. If we are already in low memory that buffer becomes the swiotlb window, no copy necessary.) -hpa -- 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/