From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754812Ab0FXU6q (ORCPT ); Thu, 24 Jun 2010 16:58:46 -0400 Received: from terminus.zytor.com ([198.137.202.10]:50114 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751483Ab0FXU6p (ORCPT ); Thu, 24 Jun 2010 16:58:45 -0400 Message-ID: <4C23C6F0.50206@zytor.com> Date: Thu, 24 Jun 2010 13:58:24 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.10) Gecko/20100621 Fedora/3.0.5-1.fc13 Thunderbird/3.0.5 MIME-Version: 1.0 To: Josh Triplett CC: Ben Hutchings , x86@kernel.org, 584846@bugs.debian.org, LKML Subject: Re: Bug#584846: Detects only 64MB and fails to boot on Intel Green City board if e820 hooked by GRUB2 References: <20100612185538.GA4511@feather> <4C13F102.7000509@zytor.com> <20100612222634.GA1785@feather> <4C141214.5050601@zytor.com> <20100613000742.GA3469@feather> <4C14235B.7030605@zytor.com> <20100622052236.GA9130@feather> <4C205323.3010509@zytor.com> <20100624072729.GA7952@feather> <4C23693A.9040107@zytor.com> <20100624190107.GA15329@feather> In-Reply-To: <20100624190107.GA15329@feather> 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 On 06/24/2010 12:01 PM, Josh Triplett wrote: > On Thu, Jun 24, 2010 at 07:18:34AM -0700, H. Peter Anvin wrote: >> On 06/24/2010 12:27 AM, Josh Triplett wrote: >>> The following patch fixes GRUB; with this patch, I can reserve memory >>> (such as with drivemap), boot 2.6.35-rc3 successfully, and it detects >>> all of my RAM. >> >> Congratulations! You have just committed the single most common BIOS >> implementation bug. (Sorry for the sarcasm, but this seems to be a bug >> that almost everyone who tries to implement BIOS makes at one point or >> another... even the original IBM BIOS had it in at least one place.) > > And a rather large number of sample interrupt code found on the web, > including the e820 hook from the version of gPXE/Etherboot that I used > as an example. :) Given that I just tested against Linux, which very > carefully works around that particular BIOS bug, I didn't run into any > issue. > > So, how high does GRUB's bug ("stc ; iret"/"clc ; iret") rank on the > list of common BIOS implementation bugs? > Less common, since that one is apparently more obvious to people (you only have to think one step ahead instead of two steps ahead.) There is a reason Linux works around this and similar bugs... it truly is extremely common (and does cause real problems in real code.) -hpa