Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933387Ab1DMWbg (ORCPT ); Wed, 13 Apr 2011 18:31:36 -0400 Received: from terminus.zytor.com ([198.137.202.10]:55971 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933313Ab1DMWbf (ORCPT ); Wed, 13 Apr 2011 18:31:35 -0400 Message-ID: <4DA6242D.90408@zytor.com> Date: Wed, 13 Apr 2011 15:31:09 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Gecko/20110307 Fedora/3.1.9-0.39.b3pre.fc14 Thunderbird/3.1.9 MIME-Version: 1.0 To: Joerg Roedel CC: Yinghai Lu , Ingo Molnar , Alex Deucher , Linus Torvalds , Linux Kernel Mailing List , dri-devel@lists.freedesktop.org, Thomas Gleixner , Tejun Heo Subject: Re: Linux 2.6.39-rc3 References: <20110412090207.GE19819@8bytes.org> <20110412184433.GF19819@8bytes.org> <20110413064609.GA18777@elte.hu> <20110413172147.GI19819@8bytes.org> <4DA5F62F.3030504@kernel.org> <20110413193459.GL19819@8bytes.org> <4DA60C30.4060606@kernel.org> <20110413215025.GA18463@8bytes.org> <4DA61D26.8050500@zytor.com> <20110413222207.GB18463@8bytes.org> In-Reply-To: <20110413222207.GB18463@8bytes.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1829 Lines: 40 On 04/13/2011 03:22 PM, Joerg Roedel wrote: > On Wed, Apr 13, 2011 at 03:01:10PM -0700, H. Peter Anvin wrote: >> On 04/13/2011 02:50 PM, Joerg Roedel wrote: >>> On Wed, Apr 13, 2011 at 01:48:48PM -0700, Yinghai Lu wrote: >>>> - addr = memblock_find_in_range(0, 1ULL<<32, aper_size, 512ULL<<20); >>>> + addr = memblock_find_in_range(0, 1ULL<<32, aper_size, 512ULL<<21); >>> >>> Btw, while looking at this code I wondered why the 512M goal is enforced >>> by the alignment. Start could be set to 512M instead and the alignment >>> can be aper_size as it should. Any reason for such a big alignment? >>> >>> Joerg >>> >>> P.S.: The box is still in the office, I will try this debug-patch >>> tomorrow. >> >> The only reason that I can think of is that the aperture itself can be >> huge, and perhaps 512 MiB is the biggest such known. > > Well, that would work as well by just using aper_size as alignment, the > aperture needs to be aligned on its size anyway. This code only runs > when Linux allocates the aperture itself and if I am mistaken is uses > always 64MB when doing this. Yes, I would agree with that. The sane thing would be to set the base to whatever address needs to be guarded against (WHICH SHOULD BE MOTIVATED), and use aper_size as alignment, *unless* we are only using the initial portion of a much larger hardware structure that needs natural alignment (which isn't clear to me, I do know we sometimes use only a fraction of the GART, but that doesn't mean we need to naturally-align the entire thing, nor that 512 MiB is sufficient to do so.) -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/