From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752774AbcHIQMX (ORCPT ); Tue, 9 Aug 2016 12:12:23 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:35758 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751088AbcHIQMT (ORCPT ); Tue, 9 Aug 2016 12:12:19 -0400 Date: Tue, 9 Aug 2016 09:12:08 -0700 From: Guenter Roeck To: Gregory CLEMENT Cc: Russell King - ARM Linux , Will Deacon , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: "Failed to create /dev/root: -14" after commit e6978e4bf1 ("ARM: save and reset the address limit when entering an exception") Message-ID: <20160809161208.GA11747@roeck-us.net> References: <57A15C41.6000804@roeck-us.net> <20160803083822.GI1041@n2100.armlinux.org.uk> <57A20896.30300@roeck-us.net> <20160804100748.GP1041@n2100.armlinux.org.uk> <87eg5y3rsk.fsf@free-electrons.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87eg5y3rsk.fsf@free-electrons.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-Authenticated_sender: guenter@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: guenter@roeck-us.net X-Authenticated-Sender: bh-25.webhostbox.net: guenter@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 09, 2016 at 05:06:51PM +0200, Gregory CLEMENT wrote: > Hi Russell King, > > On jeu., août 04 2016, Russell King - ARM Linux wrote: > > > On Wed, Aug 03, 2016 at 08:07:02AM -0700, Guenter Roeck wrote: > >> On 08/03/2016 01:38 AM, Russell King - ARM Linux wrote: > >> >On Tue, Aug 02, 2016 at 07:51:45PM -0700, Guenter Roeck wrote: > >> >>Hi, > >> >> > >> >>I see the following crash when running a qemu arm 'kzm' runtime test with > >> >>the current mainline. > >> >>... > >> >>Failed to create /dev/root: -14 > >> >> > >> >>[ followed by panic ] > >> >> > >> >>A complete log file is at [1]. > >> > > >> >I think it's because of those undefined instructions you're hitting > >> >with the hw-breakpoint code... can you try the patch below please? > >> > > >> > arch/arm/kernel/entry-armv.S | 1 + > >> > 1 file changed, 1 insertion(+) > >> > > >> >diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S > >> >index bc5f50799d75..9f157e7c51e7 100644 > >> >--- a/arch/arm/kernel/entry-armv.S > >> >+++ b/arch/arm/kernel/entry-armv.S > >> >@@ -295,6 +295,7 @@ __und_svc_fault: > >> > bl __und_fault > >> > > >> > __und_svc_finish: > >> >+ get_thread_info tsk > >> > ldr r5, [sp, #S_PSR] @ Get SVC cpsr > >> > svc_exit r5 @ return from exception > >> > UNWIND(.fnend ) > >> > > >> > >> Yes, that fixes the problem. > >> > >> Assuming you'll create a patch: > >> > >> Tested-by: Guenter Roeck > >> > >> Does that need to be addressed in qemu, or is it a Linux bug ? > > > > It's a Linux bug provoked by qemu not implementing the hardware > > breakpoints. Well worth fixing in Linux. > > The Armada XP base platform were hit by the same bug as we can see on > kernlci: > https://storage.kernelci.org/mainline/v4.8-rc1/arm-mvebu_v7_defconfig/lab-baylibre-seattle/boot-armada-xp-openblocks-ax3-4.html > > Your patch solves the issue too. > > Will you push this patch for v4.8-rc2 ? > > Also I wonder if it is something expected to have this issue on a "real" > hardware. > It would be expected if hardware breakpoint implementation is optional and not all real CPUs implement it. Guenter