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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,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 2D815C282E1 for ; Thu, 25 Apr 2019 10:22:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E50A6217D7 for ; Thu, 25 Apr 2019 10:22:40 +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="KqwenI2J" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729489AbfDYKWj (ORCPT ); Thu, 25 Apr 2019 06:22:39 -0400 Received: from merlin.infradead.org ([205.233.59.134]:49512 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726120AbfDYKWj (ORCPT ); Thu, 25 Apr 2019 06:22:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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=LkolO5taBVs8THus8l4rmFbZgwW8DG+31ulE6mh/IpA=; b=KqwenI2JUsDtJI80PRTy8Ge0Z FBmdx8ItgqZeZ5zwAt+7iIIzatkoT+yE37umBSuMRKt8o/ECl7Tw+fb7bQmeET/4STG2laWhlHDdv Mkx6LNdl2WSARDz6V36vciV+KoAme4e5baNQr2Otm+HaV8ax05BbaYiVYlA+ywmga3jBZ8MrHSTYU 2imGUOMmTpclqEbZEk7r9LjLac7WhAwvVNVY8Ae1phzV4GyEoC/FPjE6TU6iVEpgpcCNKQ3693OEq ftbjohl3fcy04oYSwuBMrlaQdOiZ7dS42KJ6UYBTxIyKbzKggWjSt25btShDVnRRMjusiFGoAmXGs jgdX9LzSA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hJbW9-0002fD-Du; Thu, 25 Apr 2019 10:22:34 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 8CA0A2395002B; Thu, 25 Apr 2019 12:22:10 +0200 (CEST) Date: Thu, 25 Apr 2019 12:22:10 +0200 From: Peter Zijlstra To: Ingo Molnar Cc: Thomas Gleixner , LKML , x86@kernel.org, Juergen Gross , Andi Kleen Subject: Re: x86/paravirt: Detect over-sized patching bugs in paravirt_patch_call() Message-ID: <20190425102210.GM4038@hirez.programming.kicks-ass.net> References: <20190424134115.091452807@linutronix.de> <20190424134223.690835713@linutronix.de> <20190425065209.GA89582@gmail.com> <20190425081012.GA115378@gmail.com> <20190425091717.GA72229@gmail.com> <20190425092131.GL4038@hirez.programming.kicks-ass.net> <20190425095039.GC115378@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190425095039.GC115378@gmail.com> 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 Thu, Apr 25, 2019 at 11:50:39AM +0200, Ingo Molnar wrote: > > * Peter Zijlstra wrote: > > > On Thu, Apr 25, 2019 at 11:17:17AM +0200, Ingo Molnar wrote: > > > It basically means that we silently won't do any patching and the kernel > > > will crash later on in mysterious ways, because paravirt patching is > > > usually relied on. > > > > That's OK. The compiler emits an indirect CALL/JMP to the pv_ops > > structure contents. That _should_ stay valid and function correctly at > > all times. > > It might result in a correctly executing kernel in terms of code > generation, but it doesn't result in a viable kernel: some of the places > rely on the patching going through and don't know what to do when it > doesn't and misbehave or crash in interesting ways. > > Guess how I know this. ;-) What sites would that be? It really should work AFAIK.