Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751374AbbF3T50 (ORCPT ); Tue, 30 Jun 2015 15:57:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40100 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750821AbbF3T5R (ORCPT ); Tue, 30 Jun 2015 15:57:17 -0400 Message-ID: <5592F49A.9080205@redhat.com> Date: Tue, 30 Jun 2015 13:57:14 -0600 From: Al Stone User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: "Rafael J. Wysocki" CC: Sudeep Holla , Al Stone , "linux-acpi@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "rjw@rjwysocki.net" , "lenb@kernel.org" , Catalin Marinas , Will Deacon , "tglx@linutronix.de" , "jason@lakedaemon.net" , "linux-kernel@vger.kernel.org" , "linaro-acpi@lists.linaro.org" , "linaro-kernel@lists.linaro.org" , "patches@linaro.org" Subject: Re: [PATCH v2 0/3] Correct for ACPI 5.1->6.0 spec changes in MADT GICC entries References: <1434666968-1543-1-git-send-email-al.stone@linaro.org> <5592CCE6.6040604@arm.com> <5592D1FF.7040208@redhat.com> <5592E26D.4070200@redhat.com> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4704 Lines: 116 On 06/30/2015 01:05 PM, Rafael J. Wysocki wrote: > Hi Al, > > On Tue, Jun 30, 2015 at 8:39 PM, Al Stone wrote: >> On 06/30/2015 12:25 PM, Rafael J. Wysocki wrote: >>> Hi Al, >>> >>> On Tue, Jun 30, 2015 at 7:29 PM, Al Stone wrote: >>>> On 06/30/2015 11:07 AM, Sudeep Holla wrote: >>>>> Hi Al, >>>>> >>>>> On 18/06/15 23:36, Al Stone wrote: >>>>>> In the ACPI 5.1 version of the spec, the struct for the GICC subtable >>>>>> (struct acpi_madt_generic_interrupt) of the MADT is 76 bytes long; in >>>>>> ACPI 6.0, the struct is 80 bytes long. But, there is only one definition >>>>>> in ACPICA for this struct -- and that is the 6.0 version. Hence, when >>>>>> BAD_MADT_ENTRY() compares the struct size to the length in the GICC >>>>>> subtable, it fails if 5.1 structs are in use, and there are systems in >>>>>> the wild that have them. >>>>>> >>>>>> Note that this was found in linux-next and these patches apply against >>>>>> that tree and the arm64 kernel tree; 4.1-rc8 does not appear to have this >>>>>> problem since it still has the 5.1 struct definition. >>>>>> >>>>>> Even though there is precendent in ia64 code for ignoring the changes in >>>>>> size, this patch set instead tries to verify correctness. The first patch >>>>>> in the set adds macros for easily using the ACPI spec version. The second >>>>>> patch adds the BAD_MADT_GICC_ENTRY() macro that uses the version macros to >>>>>> check the GICC subtable only, accounting for the difference in specification >>>>>> versions that are possible. The final patch replaces BAD_MADT_ENTRY usage >>>>>> with the BAD_MADT_GICC_ENTRY macro in arm64 code, which is currently the >>>>>> only architecture affected. The BAD_MADT_ENTRY() will continue to work as >>>>>> is for all other MADT subtables. >>>>>> >>>>> >>>>> We need to get this series or a patch to remove the check(similar to >>>>> ia64) based on what Rafael prefers. Without that, platforms using ACPI >>>>> on ARM64 fails to boot with latest mainline. This blocks any testing on >>>>> ARM64/ACPI systems. >>>>> >>>>> Regards, >>>>> Sudeep >>>> >>>> I have not received any other feedback than some Reviewed-bys from >>>> Hanjun and an ACK from Will for the arm64 patch. >>>> >>>> And absolutely agreed: this is a blocker for arm64/ACPI, starting with >>>> the ACPICA 20150515 patches which appear to have gone in with 4.2-rc1. >>>> >>>> Rafael? Ping? >>> >>> I overlooked the fact that this was needed to fix a recent regression, >>> sorry about that. >>> >>> Actually, if your patch fixes an error introduced by a specific >>> commit, it is good to use the Fixes: tag to indicate that. Which I >>> still would like to do, so which commit is fixed by this? >>> >>>> Do we need these to go through your tree or the arm64 >>>> tree? Without this series (or an ia64-like solution), we have ACPI >>>> systems in the field that cannot boot. >>> >>> I'm not quite sure why the definition of BAD_MADT_GICC_ENTRY has to go >>> into include/linux/acpi.h. Why is it necessary in there? >> >> I only placed it there since it seemed to make sense, and the issue is >> generic to ACPI, not just ARM. Granted ARM is the only arch using the >> GICC subtable in MADT, > > Precisely. > >> but this is fixing how ACPICA implemented the spec, > > So that should be fixed in ACPICA eventually and linux/acpi.h is not > an ACPICA file even. > > It is possible to apply an ACPICA fix to Linux before it goes to > upstream ACPICA if it fixes a real problem in Linux. We've done > things like that. Fair enough. I've been reluctant to add further divergence, personally. >> which in turn was ambiguous (and an errata is forthcoming to fix that). >> >> That being said, though, I'm definitely open to other possibilities. > > So I'd prefer an ACPICA fix and if that's not viable, an ARM-specific > fix to fill the gap while ACPICA is being updated. > > Thanks, > Rafael Hrm. I'll look into the ACPICA fix. I'm sure it's possible, but it may be messy. I will talk to Bob Moore and Lv Zheng about that, too. This sort of thing has surely happened before, though. In the meantime, I'll put together a new version of this patch that is ARM-specific to fill the gap. Using linux/irqchip/arm-gic-acpi.h does make sense. Thanks for all the feedback, Rafael. -- ciao, al ----------------------------------- Al Stone Software Engineer Red Hat, Inc. ahs3@redhat.com ----------------------------------- -- 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/