From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CE115C28CC6 for ; Tue, 4 Jun 2019 17:15:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B44702075B for ; Tue, 4 Jun 2019 17:15:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727959AbfFDRPz (ORCPT ); Tue, 4 Jun 2019 13:15:55 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:48372 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727822AbfFDRPy (ORCPT ); Tue, 4 Jun 2019 13:15:54 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A091780D; Tue, 4 Jun 2019 10:15:53 -0700 (PDT) Received: from [10.1.196.105] (eglon.cambridge.arm.com [10.1.196.105]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7A7C43F5AF; Tue, 4 Jun 2019 10:15:52 -0700 (PDT) Subject: Re: [PATCH 11/21] EDAC, ghes: Unify trace_mc_event() code with edac_mc driver To: Robert Richter Cc: Borislav Petkov , Tony Luck , Mauro Carvalho Chehab , "linux-edac@vger.kernel.org" , "linux-kernel@vger.kernel.org" References: <20190529084344.28562-1-rrichter@marvell.com> <20190529084344.28562-12-rrichter@marvell.com> <37d47356-a40b-2739-10df-f5ab83fa2b36@arm.com> <20190603131005.e23lovwyvii53vzo@rric.localdomain> From: James Morse Message-ID: <1fac170a-f461-a779-9e82-5b4a0fa2c154@arm.com> Date: Tue, 4 Jun 2019 18:15:50 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190603131005.e23lovwyvii53vzo@rric.localdomain> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Robert, On 03/06/2019 14:10, Robert Richter wrote: > On 29.05.19 16:12:38, James Morse wrote: >> On 29/05/2019 09:44, Robert Richter wrote: >>> Almost duplicate code, remove it. >> >>> Note: there is a difference in the calculation of the grain_bits, >>> using the edac_mc's version here. >> >> But is it the right thing to do? >> >> Is this an off-by-one bug being papered over as some cleanup? >> If so could you post a separate fix that can be picked up for an rc. >> >> Do Marvell have firmware that populates this field? >> >> ... >> >> Unless the argument is no one cares about this... >> >> >From ghes_edac_report_mem_error(): >> | /* Error grain */ >> | if (mem_err->validation_bits & CPER_MEM_VALID_PA_MASK) >> | e->grain = ~(mem_err->physical_addr_mask & ~PAGE_MASK); >> >> Fishy, why would the kernel page-size be relevant here? > > That looked broken to me too, I did not put to much effort in fixing > the grain yet. So I just took the edac_mc version first in the > assumption, that one is working. (Ah, it would have been good to note this in the commit-message) > It looks like the intention here is to limit the grain to the page > size. I'm not convinced that makes sense. If some architecture let you configure the page-size, (as arm64 does), and your hypervisor had a bigger page-size, then any hardware fault would be rounded up to hypervisor's page-size. The kernel's page-size has very little to do with the error, it only matters for when we go unmapping stuff in memory_failure(). > But right, the calculation is wrong here. I am also going to > reply to your patch you sent on this. Thanks! >> If physical_addr_mask were the same as PAGE_MASK this wouldn't this always give ~0? >> (masking logic like this always does my head in) >> >> /me gives it ago: >> | {1}[Hardware Error]: physical_address: 0x00000000deadbeef >> | {1}[Hardware Error]: physical_address_mask: 0xffffffffffff0000 >> | {1}[Hardware Error]: error_type: 6, master abort >> | EDAC MC0: 1 CE Master abort on unknown label ( page:0xdead offset:0xbeef >> | grain:-1 syndrome:0x0 - status(0x0000000000000001): reserved) >> >> That 'grain:-1' is because the calculated e->grain was an unlikely 0xffffffffffffffff. >> Patch incoming, if you could test it on your platform that'd be great. >> >> I don't think ghes_edac.c wants this '+1'. > > The +1 looks odd to me also for the edac_mc driver, but I need to take > a closer look here as well as some logs suggest the grain is > calculated correctly. My theory on this is that ghes_edac.c is generating a grain like 0x1000, fls() does the right thing. Other edac drivers are generating a grain like 0xfff to describe the same size, fls() is now off-by-one, hence the addition. I don't have a platform where I can trigger any other edac driver to test this though. The way round this would be to put the grain_bits in struct edac_raw_error_desc so that ghes_edac.c can calculate it directly. Thanks, James