Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753612Ab3IMSHb (ORCPT ); Fri, 13 Sep 2013 14:07:31 -0400 Received: from g5t0008.atlanta.hp.com ([15.192.0.45]:22895 "EHLO g5t0008.atlanta.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752046Ab3IMSHb (ORCPT ); Fri, 13 Sep 2013 14:07:31 -0400 Message-ID: <1379095648.2197.27.camel@buesod1.americas.hpqcorp.net> Subject: Re: GPT detection regression in efi.c from commit 27a7c64 From: Davidlohr Bueso To: Matt Porter Cc: Karel Zak , Matt Fleming , Linux Kernel Mailing List , torvalds@linux-foundation.org Date: Fri, 13 Sep 2013 11:07:28 -0700 In-Reply-To: <52334506.9030802@linaro.org> References: <20130913145033.GA8502@ohporter.com> <1379089736.2197.14.camel@buesod1.americas.hpqcorp.net> <52334506.9030802@linaro.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.4 (3.4.4-2.fc17) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1841 Lines: 42 On Fri, 2013-09-13 at 13:01 -0400, Matt Porter wrote: > On 09/13/2013 12:28 PM, Davidlohr Bueso wrote: > > Cc'ing Linus. > > > > On Fri, 2013-09-13 at 10:50 -0400, Matt Porter wrote: > >> The commit, "27a7c64 partitions/efi: account for pmbr size in lba", that > >> was just merged in 3.12-rc caused a regression on my system with a GPT > >> formatted eMMC device. In 3.11, the GPT partition table was detected > >> fine but now a partition table is not detected. > >> > >> Not being a GPT expert, I did some research and found that the tool used > >> to create the PMBR on my system shares characteristics with what is > >> mentioned in an explanation of Microsoft created PMBRs [1]. In short, > >> the size_in_lba field incorrectly has 0xffffffff even though I have a > >> <2TiB drive (16GiB eMMC). > > > > *sigh*. So Microsoft decided to do its own version of the GPT specs. > > Don't sound so surprised. :) > > > Up until now, Linux was incorrectly enforcing pMBR checks: not > > recognizing valid labels and vice versa, as with the case you are > > mentioning now. The changes that went in the 3.12 merge window attempt > > to address those concerns, enforcing the correct checks - which is also > > how Linux partitioning tools do it (fdisk, parted). > > Understood, and we are fixing our own manufacturing tool that was used > to prepopulate the eMMC. I definitely prefer to have this correct for my > case. Come to think of it, we do have a long existing workaround: the force_gpt option. Setting it will bypass any MBR checking (is_pmbr_valid(), specifically). Thanks, Davidlohr -- 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/