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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_NEOMUTT 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 F28D9C10F11 for ; Wed, 24 Apr 2019 15:51:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CB17F21903 for ; Wed, 24 Apr 2019 15:51:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731875AbfDXPve (ORCPT ); Wed, 24 Apr 2019 11:51:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42110 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730625AbfDXPve (ORCPT ); Wed, 24 Apr 2019 11:51:34 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D036F30BDA05; Wed, 24 Apr 2019 15:51:32 +0000 (UTC) Received: from treble (ovpn-123-99.rdu2.redhat.com [10.10.123.99]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B74BB60C64; Wed, 24 Apr 2019 15:51:23 +0000 (UTC) Date: Wed, 24 Apr 2019 10:51:20 -0500 From: Josh Poimboeuf To: Petr Mladek Cc: Jiri Kosina , Miroslav Benes , Joe Lawrence , Kamalesh Babulal , 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 Message-ID: <20190424155120.pnau7k4qaavplpnv@treble> References: <20190424085550.29612-1-pmladek@suse.com> <20190424085550.29612-2-pmladek@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190424085550.29612-2-pmladek@suse.com> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Wed, 24 Apr 2019 15:51:33 +0000 (UTC) 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 > --- > kernel/livepatch/core.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c > index eb0ee10a1981..14f33ab6c583 100644 > --- a/kernel/livepatch/core.c > +++ b/kernel/livepatch/core.c > @@ -1003,11 +1003,10 @@ int klp_enable_patch(struct klp_patch *patch) > return -ENODEV; > > if (!klp_have_reliable_stack()) { > - pr_err("This architecture doesn't have support for the livepatch consistency model.\n"); > - return -EOPNOTSUPP; > + pr_warn("This architecture doesn't have support for the livepatch consistency model.\n"); > + pr_warn("The livepatch transition may never complete.\n"); > } > > - > mutex_lock(&klp_mutex); > > ret = klp_init_patch_early(patch); > -- > 2.16.4 > Acked-by: Josh Poimboeuf -- Josh