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=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 B070EC10F11 for ; Thu, 25 Apr 2019 03:18:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 87B1F2084B for ; Thu, 25 Apr 2019 03:18:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388873AbfDYDSp (ORCPT ); Wed, 24 Apr 2019 23:18:45 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:39738 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388178AbfDYDSp (ORCPT ); Wed, 24 Apr 2019 23:18:45 -0400 Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x3P394eo146998 for ; Wed, 24 Apr 2019 23:18:44 -0400 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0a-001b2d01.pphosted.com with ESMTP id 2s31bd72k6-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 24 Apr 2019 23:18:44 -0400 Received: from localhost by e06smtp03.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 25 Apr 2019 04:18:42 +0100 Received: from b06cxnps4076.portsmouth.uk.ibm.com (9.149.109.198) by e06smtp03.uk.ibm.com (192.168.101.133) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 25 Apr 2019 04:18:40 +0100 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x3P3IcIV49676478 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 25 Apr 2019 03:18:39 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B978A52054; Thu, 25 Apr 2019 03:18:38 +0000 (GMT) Received: from JAVRIS.in.ibm.com (unknown [9.124.31.152]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTPS id 867335205F; Thu, 25 Apr 2019 03:18:37 +0000 (GMT) Date: Thu, 25 Apr 2019 08:48:32 +0530 From: Kamalesh Babulal To: Petr Mladek Cc: Jiri Kosina , Josh Poimboeuf , Miroslav Benes , Joe Lawrence , live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] livepatch: Convert error about unsupported reliable stacktrace into a warning References: <20190424085550.29612-1-pmladek@suse.com> <20190424085550.29612-2-pmladek@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190424085550.29612-2-pmladek@suse.com> User-Agent: Mutt/1.11.3 (2019-02-01) X-TM-AS-GCONF: 00 x-cbid: 19042503-0012-0000-0000-00000313E92A X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19042503-0013-0000-0000-0000214C40D6 Message-Id: <20190425031832.GA24416@JAVRIS.in.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-04-25_03:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=974 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904250020 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 24, 2019 at 10:55:48AM +0200, Petr Mladek wrote: > The commit d0807da78e11d46f ("livepatch: Remove immediate feature") caused > that any livepatch was refused when reliable stacktraces were not supported > on the given architecture. > > The limitation is too strong. User space processes are safely migrated > even when entering or leaving the kernel. Kthreads transition would > need to get forced. But it is safe when: > > + The livepatch does not change the semantic of the code. > + Callbacks do not depend on a safely finished transition. > > Suggested-by: Josh Poimboeuf > Signed-off-by: Petr Mladek Reviewed-by: Kamalesh Babulal -- Kamalesh