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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7D14DC433EF for ; Mon, 18 Oct 2021 03:08:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 549B561050 for ; Mon, 18 Oct 2021 03:08:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230121AbhJRDLE (ORCPT ); Sun, 17 Oct 2021 23:11:04 -0400 Received: from foss.arm.com ([217.140.110.172]:60082 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229445AbhJRDLD (ORCPT ); Sun, 17 Oct 2021 23:11:03 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 10A9B11D4; Sun, 17 Oct 2021 20:08:52 -0700 (PDT) Received: from [10.163.74.6] (unknown [10.163.74.6]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A75F33F73D; Sun, 17 Oct 2021 20:08:49 -0700 (PDT) Subject: Re: [PATCH v2] coresight: trbe: Defer the probe on offline CPUs To: Suzuki K Poulose , mathieu.poirier@linaro.org Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, coresight@lists.linaro.org, Bransilav Rankov , Mike Leach , Leo Yan References: <20211014142238.2221248-1-suzuki.poulose@arm.com> From: Anshuman Khandual Message-ID: Date: Mon, 18 Oct 2021 08:38:48 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20211014142238.2221248-1-suzuki.poulose@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/14/21 7:52 PM, Suzuki K Poulose wrote: > If a CPU is offline during the driver init, we could end up causing > a kernel crash trying to register the coresight device for the TRBE > instance. The trbe_cpudata for the TRBE instance is initialized only > when it is probed. Otherwise, we could end up dereferencing a NULL > cpudata->drvdata. > > e.g: > > [ 0.149999] coresight ete0: CPU0: ete v1.1 initialized > [ 0.149999] coresight-etm4x ete_1: ETM arch init failed > [ 0.149999] coresight-etm4x: probe of ete_1 failed with error -22 > [ 0.150085] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000050 > [ 0.150085] Mem abort info: > [ 0.150085] ESR = 0x96000005 > [ 0.150085] EC = 0x25: DABT (current EL), IL = 32 bits > [ 0.150085] SET = 0, FnV = 0 > [ 0.150085] EA = 0, S1PTW = 0 > [ 0.150085] Data abort info: > [ 0.150085] ISV = 0, ISS = 0x00000005 > [ 0.150085] CM = 0, WnR = 0 > [ 0.150085] [0000000000000050] user address but active_mm is swapper > [ 0.150085] Internal error: Oops: 96000005 [#1] PREEMPT SMP > [ 0.150085] Modules linked in: > [ 0.150085] Hardware name: FVP Base RevC (DT) > [ 0.150085] pstate: 00800009 (nzcv daif -PAN +UAO -TCO BTYPE=--) > [ 0.150155] pc : arm_trbe_register_coresight_cpu+0x74/0x144 > [ 0.150155] lr : arm_trbe_register_coresight_cpu+0x48/0x144 > ... > > [ 0.150237] Call trace: > [ 0.150237] arm_trbe_register_coresight_cpu+0x74/0x144 > [ 0.150237] arm_trbe_device_probe+0x1c0/0x2d8 > [ 0.150259] platform_drv_probe+0x94/0xbc > [ 0.150259] really_probe+0x1bc/0x4a8 > [ 0.150266] driver_probe_device+0x7c/0xb8 > [ 0.150266] device_driver_attach+0x6c/0xac > [ 0.150266] __driver_attach+0xc4/0x148 > [ 0.150266] bus_for_each_dev+0x7c/0xc8 > [ 0.150266] driver_attach+0x24/0x30 > [ 0.150266] bus_add_driver+0x100/0x1e0 > [ 0.150266] driver_register+0x78/0x110 > [ 0.150266] __platform_driver_register+0x44/0x50 > [ 0.150266] arm_trbe_init+0x28/0x84 > [ 0.150266] do_one_initcall+0x94/0x2bc > [ 0.150266] do_initcall_level+0xa4/0x158 > [ 0.150266] do_initcalls+0x54/0x94 > [ 0.150319] do_basic_setup+0x24/0x30 > [ 0.150319] kernel_init_freeable+0xe8/0x14c > [ 0.150319] kernel_init+0x14/0x18c > [ 0.150319] ret_from_fork+0x10/0x30 > [ 0.150319] Code: f94012c8 b0004ce2 9134a442 52819801 (f9402917) > [ 0.150319] ---[ end trace d23e0cfe5098535e ]--- > [ 0.150346] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b > > Fix this by skipping the step, if we are unable to probe the CPU. > > Fixes: 3fbf7f011f24 ("coresight: sink: Add TRBE driver") > Reported-by: Bransilav Rankov > Cc: Anshuman Khandual > Cc: Mathieu Poirier > Cc: Mike Leach > Cc: Leo Yan > Tested-by: Branislav Rankov > Signed-off-by: Suzuki K Poulose Reviewed-by: Anshuman Khandual > --- > Changes since v1: > - Explain why we crash > - Add a WARN_ON to ensure the probe was successful. > --- > drivers/hwtracing/coresight/coresight-trbe.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c > index 5d350acef798..27225b88a2fc 100644 > --- a/drivers/hwtracing/coresight/coresight-trbe.c > +++ b/drivers/hwtracing/coresight/coresight-trbe.c > @@ -1182,6 +1182,10 @@ static void arm_trbe_register_coresight_cpu(struct trbe_drvdata *drvdata, int cp > if (WARN_ON(trbe_csdev)) > return; > > + /* If the TRBE was not probed on the CPU, we shouldn't be here */ > + if (WARN_ON(!cpudata->drvdata)) > + return; > + > dev = &cpudata->drvdata->pdev->dev; > desc.name = devm_kasprintf(dev, GFP_KERNEL, "trbe%d", cpu); > if (!desc.name) > @@ -1286,7 +1290,9 @@ static int arm_trbe_probe_coresight(struct trbe_drvdata *drvdata) > return -ENOMEM; > > for_each_cpu(cpu, &drvdata->supported_cpus) { > - smp_call_function_single(cpu, arm_trbe_probe_cpu, drvdata, 1); > + /* If we fail to probe the CPU, let us defer it to hotplug callbacks */ > + if (smp_call_function_single(cpu, arm_trbe_probe_cpu, drvdata, 1)) > + continue; > if (cpumask_test_cpu(cpu, &drvdata->supported_cpus)) > arm_trbe_register_coresight_cpu(drvdata, cpu); > if (cpumask_test_cpu(cpu, &drvdata->supported_cpus)) >