From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH v4 00/13] "Task_isolation" mode Date: Thu, 23 Jul 2020 16:26:23 +0200 Message-ID: <20200723142623.GS5523@worktop.programming.kicks-ass.net> References: <04be044c1bcd76b7438b7563edc35383417f12c8.camel@marvell.com> <87imeextf3.fsf@nanos.tec.linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48840 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726089AbgGWO0g (ORCPT ); Thu, 23 Jul 2020 10:26:36 -0400 Content-Disposition: inline In-Reply-To: <87imeextf3.fsf@nanos.tec.linutronix.de> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Thomas Gleixner Cc: Alex Belits , "frederic@kernel.org" , "rostedt@goodmis.org" , Prasun Kapoor , "mingo@kernel.org" , "davem@davemloft.net" , "linux-api@vger.kernel.org" , "linux-arch@vger.kernel.org" , "catalin.marinas@arm.com" , "will@kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" On Thu, Jul 23, 2020 at 03:17:04PM +0200, Thomas Gleixner wrote: > 2) Instruction synchronization > > Trying to do instruction synchronization delayed is a clear recipe > for hard to diagnose failures. Just because it blew not up in your > face does not make it correct in any way. It's broken by design and > violates _all_ rules of safe instruction patching and introduces a > complete trainwreck in x86 NMI processing. > > If you really think that this is correct, then please have at least > the courtesy to come up with a detailed and precise argumentation > why this is a valid approach. > > While writing that up you surely will find out why it is not. So delaying the sync_core() IPIs for kernel text patching _might_ be possible, but it very much wants to be a separate patchset and not something hidden inside a 'gem' like this.