Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751320Ab3IPQX5 (ORCPT ); Mon, 16 Sep 2013 12:23:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56046 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750932Ab3IPQXz (ORCPT ); Mon, 16 Sep 2013 12:23:55 -0400 Message-ID: <523730F2.40408@redhat.com> Date: Mon, 16 Sep 2013 18:25:22 +0200 From: Laszlo Ersek User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130806 Thunderbird/17.0.8 MIME-Version: 1.0 To: Josh Triplett CC: Matt Fleming , jerry.hoemann@hp.com, Andrew Fish , edk2-devel@lists.sourceforge.net, linux-efi@vger.kernel.org, Gleb Natapov , lkml , David Woodhouse , Matthew Garrett , Brian Richardson , Colin Ian King , Randy Wright , Linn Crosetto , terry.lee@hp.com, samer.el-haj-mahmoud@hp.com, randy.pawell@hp.com, chrisp@hp.com, linda.knippers@hp.com, dong.wei@hp.com, "H. Peter Anvin" , Borislav Petkov , Chao Zhang , Yao Jiewen Subject: Re: [edk2] Corrupted EFI region References: <20130806141036.GD14891@pd.tnic> <520116D1.2010000@redhat.com> <20130807151935.GJ17920@pd.tnic> <20130807201908.GG2515@console-pimps.org> <20130808101730.GJ2515@console-pimps.org> <20130913203812.GA312@anatevka.fc.hp.com> <20130916105920.GB2697@console-pimps.org> <5236F096.8040702@redhat.com> <20130916155751.GA3636@leaf> In-Reply-To: <20130916155751.GA3636@leaf> 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 Content-Length: 2275 Lines: 58 On 09/16/13 17:57, Josh Triplett wrote: >> The edk2 commit that flipped the memory type underneath the image data >> from EfiReservedMemoryType to EfiBootServicesData is: >> >> https://github.com/tianocore/edk2/commit/4c58575e >> >> I think this commit is wrong. It's fine for OSPM to release the image >> data at some point, but not right after ExitBootServices(), because >> referencing pointers in ACPI tables survive strictly longer. >> >> ... Actually, the commit does follow the ACPI spec 5.0: >> >> 5.2.22.4 Image Address >> >> The Image Address contains the location in memory where an >> in-memory copy of the boot image can be found. The image should be >> stored in EfiBootServicesData, allowing the system to reclaim >> the memory when the image is no longer needed. >> >> The ACPI spec 5.0 should recommend EfiACPIReclaimMemory here IMO. (I >> take the current wording ("should be stored") as a recommendation only.) > > I agree that UEFI *should* store the BGRT in EfiACPIReclaimMemory, but > in practice the UEFI firmware I've seen with a BGRT does follow that > recommendation and store it in EfiBootServicesData. So, even if the > recommendation in the spec changed, the kernel would still have to > accomodate both possibilities. Just for the theoretical debate: The edk2 commit linked above is 5 days old. All UEFI firmware in the wild (on released hardware) should be using EfiReservedMemoryType (the pre-patch memory type), which is even stricter. EfiReservedMemoryType can never be released & repurposed, so it should make no difference for crash kernel allocation, shouldn't it? - call efi_free_boot_services() -- doesn't touch the image data (which is in RAM of EfiReservedMemoryType), - reserve crash kernel, - access BGRT via ACPI. BGRT had appeared in edk2 with https://github.com/tianocore/edk2/commit/0284e90c and EfiReservedMemoryType used to be the allocation type until commit 4c58575e. Or are you alluding to UEFI firmware that's not based on TianoCore? Laszlo -- 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/