Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758700AbXHXRHz (ORCPT ); Fri, 24 Aug 2007 13:07:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755493AbXHXRHq (ORCPT ); Fri, 24 Aug 2007 13:07:46 -0400 Received: from mx2.suse.de ([195.135.220.15]:54229 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754029AbXHXRHq (ORCPT ); Fri, 24 Aug 2007 13:07:46 -0400 Date: Fri, 24 Aug 2007 19:07:44 +0200 From: Andi Kleen To: Andy Whitcroft Cc: Andi Kleen , Mel Gorman , linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86 Boot NUMA kernels on non-NUMA hardware with DISCONTIG memory model Message-ID: <20070824170744.GB16227@bingen.suse.de> References: <20070824162814.GD26374@skynet.ie> <20070824163521.GA16227@bingen.suse.de> <46CF0CCF.7010702@shadowen.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <46CF0CCF.7010702@shadowen.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1408 Lines: 37 On Fri, Aug 24, 2007 at 05:52:31PM +0100, Andy Whitcroft wrote: > Andi Kleen wrote: > >> This reserved portion of the KVA must be PMD aligned. > > > > Why do they need to be PMD aligned? > > That comes from the fact that the KVA in x86 has traditionally been Where does this KVA acronym come from? In Linux this is traditionally called direct or linear mapping. KVA sounds foreign. > mapped with huge pages where at all possible, for performance reasons. It was partly a rhetorical question. My point is that we don't make any effort to PMD align end_pfn, so there is also no reason to PMD align any of the other boundaries. The only reason in theory is to avoid virtual aliases with uncached areas, but there are no uncached areas in highmem so this shouldn't be a concern. There might be overlap into the PCI hole though which is uncached and needs care rgarding virtual aliases, but that could be handled by teaching change_page_attr() to handle the overlap too. I think that would be a better fix -- do that and then drop that PMD align requirement. Essentially you need a end_pfn_map like x86_64 has and use that in change_page_attr(). -Andi - 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/