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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 351A6CA9EBC for ; Fri, 25 Oct 2019 08:43:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0DA732070B for ; Fri, 25 Oct 2019 08:43:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="D8BWFPd3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2408413AbfJYInN (ORCPT ); Fri, 25 Oct 2019 04:43:13 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:58154 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2408361AbfJYInN (ORCPT ); Fri, 25 Oct 2019 04:43:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=/9XjHHhi9cmHqBCDafIhrq5RljTOrxtN4eiY5hNBvRw=; b=D8BWFPd3KhZg5ubJIgIjUHoO6 7lbcZxfhDOuR8J8Ne1ba5PEghIoeC8Bq3rNF+b+jNOirqQx2WARbWho8w7sy+gPTIO+p5snNBPLh9 +ASQb/C6jqvqsZzs1Vaf0bB7xzqbUxwTiPH24ze2HDrSN4+0xSLcdzX1H/opAcBt6Z9Sf9/5R7p3b dmNYaMTXq4uPTT6mgRHd4LrLoPiYFjkY8sSt4WP4jWDyu1pTITquH/+Ch/uFABr0QuVlJqtPxAROB arFPZQIfT1JXQAyhJ+TW+DYMM14fPcwZ+N7fE4ClKRf0rHBrPxntz089yDd5Q2DbE0u0PWgQhqBFT Z+bgFkw/w==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iNvBW-0004YE-JM; Fri, 25 Oct 2019 08:43:02 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 91DF9303DA1; Fri, 25 Oct 2019 10:42:01 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 64768201A660C; Fri, 25 Oct 2019 10:43:00 +0200 (CEST) Date: Fri, 25 Oct 2019 10:43:00 +0200 From: Peter Zijlstra To: Petr Mladek Cc: Josh Poimboeuf , x86@kernel.org, linux-kernel@vger.kernel.org, rostedt@goodmis.org, mhiramat@kernel.org, bristot@redhat.com, jbaron@akamai.com, torvalds@linux-foundation.org, tglx@linutronix.de, mingo@kernel.org, namit@vmware.com, hpa@zytor.com, luto@kernel.org, ard.biesheuvel@linaro.org, jeyu@kernel.org, live-patching@vger.kernel.org Subject: Re: [PATCH v4 15/16] module: Move where we mark modules RO,X Message-ID: <20191025084300.GG4131@hirez.programming.kicks-ass.net> References: <20191018073525.768931536@infradead.org> <20191018074634.801435443@infradead.org> <20191021135312.jbbxsuipxldocdjk@treble> <20191021141402.GI1817@hirez.programming.kicks-ass.net> <20191023114835.GT1817@hirez.programming.kicks-ass.net> <20191023170025.f34g3vxaqr4f5gqh@treble> <20191024131634.GC4131@hirez.programming.kicks-ass.net> <20191025064456.6jjrngm4m3mspaxw@pathway.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191025064456.6jjrngm4m3mspaxw@pathway.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 25, 2019 at 08:44:56AM +0200, Petr Mladek wrote: > On Thu 2019-10-24 15:16:34, Peter Zijlstra wrote: > > On Wed, Oct 23, 2019 at 12:00:25PM -0500, Josh Poimboeuf wrote: > > > > > > This then raises a number of questions: > > > > > > > > 1) why is that RELA (that obviously does not depend on any module) > > > > applied so late? > > > > > > Good question. The 'pv_ops' symbol is exported by the core kernel, so I > > > can't see any reason why we'd need to apply that rela late. In theory, > > > kpatch-build isn't supposed to convert that to a klp rela. Maybe > > > something went wrong in the patch creation code. > > > > > > I'm also questioning why we even need to apply the parainstructions > > > section late. Maybe we can remove that apply_paravirt() call > > > altogether, along with .klp.arch.parainstruction sections. > > Hmm, the original bug report against livepatching was actually about > paravirt ops, see below. Yes, I found that. > > > I'm not sure about alternatives, but maybe we can enforce such > > > limitations with tooling and/or kernel checks. > > > > Right, so on IRC you implied you might have some additional details on > > how alternatives were affected; did you manage to dig that up? > > I am not sure what Josh had in mind. But the problem with livepatches, > paravort ops, and alternatives was described in the related patchset, see > https://lkml.kernel.org/r/1471481911-5003-1-git-send-email-jeyu@redhat.com Yes, and my complaint there is that that thread is void of useful content. > The original bug report is > https://lkml.kernel.org/r/20160329120518.GA21252@canonical.com I found the github (*groan*) link in the thread above. >From all that I could only make that the paravirt stuff is just doing it wrong (see earlier emails, core-kernel RELAs really should be applied at the time of patch-module load, there's no excuse for them to be delayed to the .klp.rela. section) at which point paravirt will also magically work. But none of that explains why apply_alternatives() is also delayed. So I'm very tempted to just revert that patchset for doing it all wrong.