From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751529AbdITDF4 (ORCPT ); Tue, 19 Sep 2017 23:05:56 -0400 Received: from ozlabs.org ([103.22.144.67]:55531 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751284AbdITDFz (ORCPT ); Tue, 19 Sep 2017 23:05:55 -0400 From: Michael Ellerman To: Guenter Roeck , Christophe Leroy Cc: linux-kernel@vger.kernel.org, Benjamin Herrenschmidt , linuxppc-dev@lists.ozlabs.org, Paul Mackerras Subject: Re: Traceback due to 'powerpc/mm: Fix kernel RAM protection...' when running ppc image in qemu In-Reply-To: <20170919182459.GA7933@roeck-us.net> References: <20170919182459.GA7933@roeck-us.net> User-Agent: Notmuch/0.21 (https://notmuchmail.org) Date: Wed, 20 Sep 2017 13:05:48 +1000 Message-ID: <8760ce9iib.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Guenter Roeck writes: > Hi, > > I see a the following traceback when running an SMP image based on > 85xx/mpc85xx_cds_defconfig in qemu. > > ------------[ cut here ]------------ > WARNING: CPU: 0 PID: 1 at kernel/smp.c:416 smp_call_function_many+0xcc/0x2fc > CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.14.0-rc1-00009-g0666f56 #1 > task: cf830000 task.stack: cf82e000 > NIP: c00a93c8 LR: c00a9634 CTR: 00000001 > REGS: cf82fde0 TRAP: 0700 Not tainted (4.14.0-rc1-00009-g0666f56) > MSR: 00021000 CR: 24000082 XER: 00000000 > > GPR00: c00a9634 cf82fe90 cf830000 c050ad3c c0015a54 00000000 00000001 00000001 > GPR08: 00000001 00000000 00000000 cf82e000 24000084 00000000 c0003150 00000000 > GPR16: 00000000 00000000 00000000 00000000 00000000 00000001 00000000 c0510000 > GPR24: 00000000 c0015a54 00000000 c050ad3c c051823c c050ad3c 00000025 00000000 > NIP [c00a93c8] smp_call_function_many+0xcc/0x2fc > LR [c00a9634] smp_call_function+0x3c/0x50 > Call Trace: > [cf82fe90] [00000010] 0x10 (unreliable) > [cf82fed0] [c00a9634] smp_call_function+0x3c/0x50 > [cf82fee0] [c0015d2c] flush_tlb_kernel_range+0x20/0x38 > [cf82fef0] [c001524c] mark_initmem_nx+0x154/0x16c > [cf82ff20] [c001484c] free_initmem+0x20/0x4c > [cf82ff30] [c000316c] kernel_init+0x1c/0x108 > [cf82ff40] [c000f3a8] ret_from_kernel_thread+0x5c/0x64 > Instruction dump: > 7c0803a6 7d808120 38210040 4e800020 3d20c052 812981a0 2f890000 40beffac > 3d20c051 8929ac64 2f890000 40beff9c <0fe00000> 4bffff94 7fc3f378 7f64db78 > ---[ end trace 7da7bdcf8b15ddb3 ]--- Thanks. I guess the system still runs OK otherwise, you're just seeing the warning? > A complete log is available at: > http://kerneltests.org/builders/qemu-ppc-master/builds/814/steps/qemubuildcommand/logs/stdio > > Bisect points to commit 3184cc4b6f6a1dc0 ("powerpc/mm: Fix kernel RAM protection > after freeing unused memory on PPC32"). Bisect log is attached. A quick look > suggests that mark_initmem_nx() is called with interrupts disabled, which > triggers the traceback. Hmm. Yes the MSR says you have interrupts disabled (EE missing). But I don't see why. start_kernel() did local_irq_enable(), so I don't understand why we got to mark_initmem_nx() with them disabled. I'll hope that Christophe has some idea. cheers