Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933519AbYB2S5K (ORCPT ); Fri, 29 Feb 2008 13:57:10 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760939AbYB2S4z (ORCPT ); Fri, 29 Feb 2008 13:56:55 -0500 Received: from out3.smtp.messagingengine.com ([66.111.4.27]:40246 "EHLO out3.smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758161AbYB2S4y (ORCPT ); Fri, 29 Feb 2008 13:56:54 -0500 Message-Id: <1204311412.28554.1239873349@webmail.messagingengine.com> X-Sasl-Enc: K8EyqEwKdtpSOjc+SAYjsuTe69DMPJCZvj8g3tPtaIkm 1204311412 From: "Alexander van Heukelum" To: "H. Peter Anvin" Cc: "Mark McLoughlin" , "Alexander van Heukelum" , "Ingo Molnar" , "Ian Campbell" , "Andi Kleen" , "Thomas Gleixner" , "Jeremy Fitzhardinge" , "LKML" Content-Disposition: inline Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="ISO-8859-1" MIME-Version: 1.0 X-Mailer: MessagingEngine.com Webmail Interface References: <20080224174605.GA21661@mailshack.com> <47C22568.1010405@zytor.com> <1203958478.20033.1239002461@webmail.messagingengine.com> <20080225170134.GA15839@elte.hu> <20080225180750.GA31054@mailshack.com> <20080228131341.GA25213@mailshack.com> <1204232996.28798.8.camel@cthulhu.hellion.org.uk> <20080229114943.GA1909@mailshack.com> <1204305247.2037.2.camel@muff> <1204310323.24514.1239870063@webmail.messagingengine.com> <47C85294.9030902@zytor.com> Subject: Re: [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit In-Reply-To: <47C85294.9030902@zytor.com> Date: Fri, 29 Feb 2008 19:56:52 +0100 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1375 Lines: 48 On Fri, 29 Feb 2008 10:44:36 -0800, "H. Peter Anvin" said: > Alexander van Heukelum wrote: > > > > My first guess is that the BIOS data area is completely non-existent for > > Xen. > > Is it guaranteed that the memory is zeroed out on boot? In that case we > > can > > special-case it easily: > > > > change: > > /* Paranoia: should never happen, but... */ > > if (lowmem >= 0x100000) > > lowmem = 0xa0000; > > > > into: > > /* Strange case, like Xen ;) */ > > if (lowmem == 0 || lowmem >= 0x100000) > > lowmem = 0x9f000; > > > > Can you test that? > > > > The EBDA is optional anyway; I presume it should have a zero pointer if > it isn't present. Correct, but the value that indicates the size of the conventional memory area must be set. At least on any real hardware. My guess is that both values read as 0 on Xen, which causes 0-0x100000 to be reserved. If that is always the case the workaround is fine, I think. Alexander > -hpa -- Alexander van Heukelum heukelum@fastmail.fm -- http://www.fastmail.fm - mmm... Fastmail... -- 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/