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spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732122AbeGaCJK (ORCPT ); Mon, 30 Jul 2018 22:09:10 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:48102 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732009AbeGaCJJ (ORCPT ); Mon, 30 Jul 2018 22:09:09 -0400 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.22/8.16.0.22) with SMTP id w6V0TL0o051046; Tue, 31 Jul 2018 00:31:18 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=Vza+M7HZa0POrLWJ9es7E64+cpDMtjGGL4/kKVG6OVI=; b=ZfrQG286GJLMevzhFThs98eW00x5TDlHWbhuFwCsFvY5fOOXfG/DbWcOffe3Ox7+TWNj o1kefZiZEAnAN/vP7gDLLrqTF++fRa937L9RR1pdBMPucdC1lSqFAaMgD5HRqiyHnAwS J9lNhZvLPyItYK7QLD0hOTnrkc5Ui5IRbbvgFGX1tWBVw/94uslzv8Er/5YXhMzw1Vpf TD5jgXnLBF3rWBw/25o7o7H2tXzouuN2bPgZr6uyd3Zyh/yzyCTSDGmSEKJD5FaYFalP ClaLifrq4I4RRr0rwg2SxjE58ligi3HLjU6QFCJESmHwIeGnsi4QUWJcR1dqFUteyluq 5A== Received: from userv0021.oracle.com (userv0021.oracle.com [156.151.31.71]) by userp2120.oracle.com with ESMTP id 2kgh4pxp0q-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 31 Jul 2018 00:31:18 +0000 Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userv0021.oracle.com (8.14.4/8.14.4) with ESMTP id w6V0VHAt025033 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 31 Jul 2018 00:31:17 GMT Received: from abhmp0006.oracle.com (abhmp0006.oracle.com [141.146.116.12]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id w6V0VGBe003403; Tue, 31 Jul 2018 00:31:17 GMT Received: from [192.168.1.93] (/99.156.91.244) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 30 Jul 2018 17:31:16 -0700 Subject: Re: [PATCH 1/1] arm64: kexec: machine_kexec should call __flush_icache_range To: AKASHI Takahiro , Will Deacon , Catalin Marinas , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20180730161641.6zxxy3lxp27tznck@armageddon.cambridge.arm.com> <20180730162235.GC4276@arm.com> <2651847f-79ea-fe2a-c1d7-efe4d11702b4@oracle.com> <20180730165757.GF4276@arm.com> <20180731002830.GJ11258@linaro.org> From: Dave Kleikamp Openpgp: preference=signencrypt Message-ID: <86e4ea58-a9d7-c4ab-97e4-b8be256fc954@oracle.com> Date: Mon, 30 Jul 2018 19:31:16 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180731002830.GJ11258@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8970 signatures=668706 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1806210000 definitions=main-1807310004 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/30/2018 07:28 PM, AKASHI Takahiro wrote: > On Mon, Jul 30, 2018 at 04:36:28PM -0500, Dave Kleikamp wrote: >> On 07/30/2018 11:57 AM, Will Deacon wrote: >>> On Mon, Jul 30, 2018 at 11:46:24AM -0500, Dave Kleikamp wrote: >>>> On 07/30/2018 11:22 AM, Will Deacon wrote: >>>>> On Mon, Jul 30, 2018 at 05:16:42PM +0100, Catalin Marinas wrote: >>>>>> On Mon, Jul 30, 2018 at 10:29:21AM -0500, Dave Kleikamp wrote: >>>>>>> machine_kexec flushes the reboot_code_buffer from the icache >>>>>>> after stopping the other cpus. >>>>>>> >>>>>>> Commit 3b8c9f1cdfc5 ("arm64: IPI each CPU after invalidating the I-cache >>>>>>> for kernel mappings") added an IPI call to flush_icache_range, which >>>>>>> causes a hang here, so replace the call with __flush_icache_range >>>>>> >>>>>> While machine_kexec() may be called with interrupts disabled (IIUC) and >>>>>> we shouldn't IPI other CPUs, I don't understand why it hangs here. Are >>>>>> there any other CPUs online at this point? >>>>> >>>>> The BUG_ON and WARN_ON at the start of machine_kexec() suggest to me that >>>>> this should only happen if we're kexec'ing a crash kernel and >>>>> smp_crash_stop_failed(). Is that something we need to care about? >>>> >>>> I observed the hang trying to kexec a crash kernel and I did not see the >>>> warning that smp_crash_stop_failed(). I'm not exactly sure why >>>> flush_icache_range() hung (but it did), but I think that >>>> __flush_icache_range() makes more sense here anyway. >>> >>> Yeah, I'll pick the patch up, but it would be nice to understand the >>> failure case you observed. >> >> I see why it failed. ipi_cpu_crash_stop() does not call >> set_cpu_online(cpu, false) the way ipi_cpu_stop() does. So >> cpu_online_mask is still populated with the stopped cpus. >> >> Any reason why it isn't called there? > > Because I wanted that saved cpu-related state be as close to as it was > at panic. > If cpus go offline, the core dump would show that all the cores but > a panicked one be offline whether or not they actually were. That makes sense. Thanks, Dave > > Thanks, > -Takahiro AKASHI > >> Thanks, >> Dave >> >>> >>> Will >>>