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=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,WEIRD_PORT autolearn=no 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 08AB9C433DB for ; Wed, 24 Feb 2021 08:54:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A01C664ECB for ; Wed, 24 Feb 2021 08:54:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234418AbhBXIxw (ORCPT ); Wed, 24 Feb 2021 03:53:52 -0500 Received: from mail.kernel.org ([198.145.29.99]:37460 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234598AbhBXIxO (ORCPT ); Wed, 24 Feb 2021 03:53:14 -0500 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 378FF64ECB; Wed, 24 Feb 2021 08:52:33 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94) (envelope-from ) id 1lEpuI-00Fe18-UX; Wed, 24 Feb 2021 08:52:31 +0000 Date: Wed, 24 Feb 2021 08:52:30 +0000 Message-ID: <877dmx26gh.wl-maz@kernel.org> From: Marc Zyngier To: Guillaume Tucker Cc: Will Deacon , Catalin Marinas , David Brazdil , Ard Biesheuvel , Amit Daniel Kachhap , Vincenzo Frascino , linux-arm-kernel@lists.infradead.org, Mark Brown , Mark Rutland , linux-kernel@vger.kernel.org, Andrey Konovalov , Remi Denis-Courmont , "kernelci-results@groups.io" Subject: Re: mainline/master bisection: baseline.login on meson-sm1-khadas-vim3l In-Reply-To: References: <6033a5da.1c69fb81.9be93.66e6@mx.google.com> <00e098ec-671b-1117-c9c6-7f8fa96519f7@collabora.com> <87blca27fy.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: guillaume.tucker@collabora.com, will@kernel.org, catalin.marinas@arm.com, dbrazdil@google.com, ardb@kernel.org, amit.kachhap@arm.com, vincenzo.frascino@arm.com, linux-arm-kernel@lists.infradead.org, broonie@kernel.org, mark.rutland@arm.com, linux-kernel@vger.kernel.org, andreyknvl@google.com, remi.denis.courmont@huawei.com, kernelci-results@groups.io X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 23 Feb 2021 21:03:52 +0000, Guillaume Tucker wrote: > > On 23/02/2021 14:18, Marc Zyngier wrote: > > Hi Guillaume, > > > > On Tue, 23 Feb 2021 09:46:30 +0000, > > Guillaume Tucker wrote: > >> > >> Hello Marc, > >> > >> Please see the bisection report below about a boot failure on > >> meson-sm1-khadas-vim3l on mainline. It seems to only be > >> affecting kernels built with CONFIG_ARM64_64K_PAGES=y. > >> > >> Reports aren't automatically sent to the public while we're > >> trialing new bisection features on kernelci.org but this one > >> looks valid. > >> > >> There's no output in the log, so the kernel is most likely > >> crashing early. Some more details can be found here: > >> > >> https://kernelci.org/test/case/id/6034bed3b344e2860daddcc8/ > >> > >> Please let us know if you need any help to debug the issue or try > >> a fix on this platform. > > > > Thanks for the heads up. > > > > There is actually a fundamental problem with the patch you bisected > > to: it provides no guarantee that the point where we enable the EL2 > > MMU is in the idmap and, as it turns out, the code we're running from > > disappears from under our feet, leading to a translation fault we're > > not prepared to handle. > > > > How does it work with 4kB pages? Luck. > > There may be a fascinating explanation for it, but luck works > too. It really seems to be booting happily with 4k pages: > > https://kernelci.org/test/plan/id/60347b358de339d1b7addcc5/ Oh, I know it boots fine with 4k, that's what I used everywhere. We're just lucky that the bit of code that deals with the MMU happens to *also* be in the idmap. With 64k pages, it gets pushed further down the line, and bad things happen. Short of explicit statements in the code, luck rules. > > > Do you mind giving the patch below a go? It does work on my vim3l and > > on a FVP, so odds are that it will solve it for you too. > > Sure, and that worked here as well: > > http://lava.baylibre.com:10080/scheduler/job/752416 > > and here's the test branch where I applied your fix, for > completeness: > > https://gitlab.collabora.com/gtucker/linux/-/commits/v5.11-vim3l-vhe/ Awesome. thanks for having tested it. > As always, if you do send a patch with the fix, please give some > credit to the bot: > > Reported-by: "kernelci.org bot" Will do. Mind if I credit you too for the testing? Thanks, M. -- Without deviation from the norm, progress is not possible.