From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: [PATCH 28/31] memblock: Export MEMBLOCK_ERROR again Date: Wed, 28 Jul 2010 16:29:52 +1000 Message-ID: <1280298592.1970.248.camel@pasglop> References: <1279822864-17154-1-git-send-email-yinghai@kernel.org> <1279822864-17154-29-git-send-email-yinghai@kernel.org> <1280294128.1970.237.camel@pasglop> <1280294376.1970.239.camel@pasglop> <4C4FC5D1.3070708@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from gate.crashing.org ([63.228.1.57]:35151 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752959Ab0G1Ga0 (ORCPT ); Wed, 28 Jul 2010 02:30:26 -0400 In-Reply-To: <4C4FC5D1.3070708@zytor.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: "H. Peter Anvin" Cc: Yinghai Lu , Ingo Molnar , Thomas Gleixner , Andrew Morton , David Miller , Linus Torvalds , Johannes Weiner , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org On Tue, 2010-07-27 at 22:53 -0700, H. Peter Anvin wrote: > On 07/27/2010 10:19 PM, Benjamin Herrenschmidt wrote: > > > > Screw it, I don't like it but I'll just split your patch in two for now > > and keep 0. It's a bit fishy but memblock does mostly top-down > > allocations and so shouldn't hit 0, and in practice the region at 0 is, > > I beleive, reserved, but we need to be extra careful and might need to > > revisit that a bit. > > > > That's an area where I don't completely agree with Linus, ie, 0 is a > > perfectly valid physical address for memblock to return :-) > > > > On x86, physical address 0 contains the real-mode IVT and will thus be > reserved, at least for the forseeable future. Other architectures may > very well have non-special RAM there. Right, that's my point. Anyways, I'm making 0 special for now and adding a wart to prevent the allocator from returning something below PAGE_SIZE. If we want to revisit that later we can. Cheers, Ben.