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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 5E14EC34047 for ; Wed, 19 Feb 2020 14:21:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2DAFF24656 for ; Wed, 19 Feb 2020 14:21:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727851AbgBSOVR (ORCPT ); Wed, 19 Feb 2020 09:21:17 -0500 Received: from mail.kernel.org ([198.145.29.99]:51100 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726736AbgBSOVR (ORCPT ); Wed, 19 Feb 2020 09:21:17 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B03B6206ED; Wed, 19 Feb 2020 14:21:16 +0000 (UTC) Date: Wed, 19 Feb 2020 09:21:15 -0500 From: Steven Rostedt To: Peter Zijlstra Cc: Andy Lutomirski , Borislav Petkov , Tony Luck , x86-ml , lkml Subject: Re: [RFC] #MC mess Message-ID: <20200219092115.3b3cccd9@gandalf.local.home> In-Reply-To: <20200219081541.GG14914@hirez.programming.kicks-ass.net> References: <20200218173150.GK14449@zn.tnic> <20200219081541.GG14914@hirez.programming.kicks-ass.net> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 19 Feb 2020 09:15:41 +0100 Peter Zijlstra wrote: > > > > Tony, etc, can you ask your Intel contacts who care about this kind of > > thing to stop twiddling their thumbs and FIX IT? The easy fix is > > utterly trivial. Add a new instruction IRET_NON_NMI. It does > > *exactly* the same thing as IRET except that it does not unmask NMIs. > > (It also doesn't unmask NMIs if it faults.) No fancy design work. > > Future improvements can still happen on top of this. > > Yes please! Of course, we're stuck with the existing NMI entry crap > forever because legacy, but it would make all things NMI so much saner. What would be nice is to have a NMI_IRET, that is defined as something that wont break legacy CPUs. Where it could be just a nop iret, or maybe if possible a "lock iret"? That is, not have a IRET_NON_NMI, as that would be all over the place, but just the iret for NMI itself. As that's in one place. -- Steve