Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751716AbaG1SPZ (ORCPT ); Mon, 28 Jul 2014 14:15:25 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:45828 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751151AbaG1SPX (ORCPT ); Mon, 28 Jul 2014 14:15:23 -0400 Date: Mon, 28 Jul 2014 19:14:56 +0100 From: Will Deacon To: Konstantin Khlebnikov Cc: Russell King , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Vitaly Andrianov , Cyril Chemparathy Subject: Re: [PATCH 2/2] ARM: LPAE: reduce damage caused by idmap to virtual memory layout Message-ID: <20140728181456.GO15536@arm.com> References: <20140722153623.25088.37742.stgit@buzz> <20140722153635.25088.14197.stgit@buzz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140722153635.25088.14197.stgit@buzz> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 22, 2014 at 04:36:35PM +0100, Konstantin Khlebnikov wrote: > idmap layout combines both phisical and virtual addresses. > Everything works fine if ram physically lays below PAGE_OFFSET. > Otherwise idmap starts punching huge holes in virtual memory layout. > It maps ram by 2MiB sections, but when it allocates new pmd page it > cuts 1GiB at once. > > This patch makes a copy of all affected pmds from init_mm. > Only few (usually one) 2MiB sections will be lost. > This is not eliminates problem but makes it 512 times less likely. I'm struggling to understand your commit message, but making a problem `512 times less likely' does sound like a bit of a hack to me. Can't we fix this properly instead? Will -- 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/