Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755361Ab1DRPwf (ORCPT ); Mon, 18 Apr 2011 11:52:35 -0400 Received: from terminus.zytor.com ([198.137.202.10]:43712 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754442Ab1DRPw3 (ORCPT ); Mon, 18 Apr 2011 11:52:29 -0400 Message-ID: <4DAC5E16.1020408@zytor.com> Date: Mon, 18 Apr 2011 08:51:50 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Gecko/20110403 Fedora/3.1.9-6.fc15 Thunderbird/3.1.9 MIME-Version: 1.0 To: "Roedel, Joerg" CC: Ingo Molnar , Thomas Gleixner , "x86@kernel.org" , "linux-kernel@vger.kernel.org" , Yinghai Lu Subject: Re: [PATCH 1/4] x86, gart: Don't enforce GART aperture lower-bound by alignment References: <1303134346-5805-1-git-send-email-joerg.roedel@amd.com> <1303134346-5805-2-git-send-email-joerg.roedel@amd.com> <4DAC4E7F.1010502@zytor.com> <20110418145653.GI2192@amd.com> In-Reply-To: <20110418145653.GI2192@amd.com> 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: 1811 Lines: 41 On 04/18/2011 07:56 AM, Roedel, Joerg wrote: > On Mon, Apr 18, 2011 at 10:45:19AM -0400, H. Peter Anvin wrote: >> On 04/18/2011 06:45 AM, Joerg Roedel wrote: >>> This patch changes the allocation of the GART aperture to >>> enforce only natural alignment instead of aligning it on >>> 512MB. This big alignment was used to force the GART >>> aperture to be over 512MB. This is enforced by using 512MB >>> as the lower-bound address in the allocation range. >>> >>> Cc: Yinghai Lu >>> Signed-off-by: Joerg Roedel >> >> Better implementation of the existing bounds, yes, but I think the >> algorithm is still wrong. Specifically, 512 MiB seems to have been the >> maximum address of the kernel at some point, but that is historic at >> this point, at least on 64 bits. > > I am fine with a smaller lower-bound, but I am not sure what a better > choice is. The comment about kexec seems to be valid. It shouldn't matter > for kdump because in this case the memory is allocated independently and > the kdump kernel will only use this part, but for other kexec uses it is > a bit harder. Probably any number we choose as a lower bound is an > arbitrary choice at some point. But I am open for > suggestions/corrections to this. > The right thing to do for in-place kexec it to turn it off, not rely on any specific magic addresses. We have had this problem with a number of drivers in the context of kexec. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- 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/