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, URIBL_BLOCKED,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 71BFCC34047 for ; Wed, 19 Feb 2020 15:05:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 44F74208C4 for ; Wed, 19 Feb 2020 15:05:28 +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="1YTSyvj8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726773AbgBSPF1 (ORCPT ); Wed, 19 Feb 2020 10:05:27 -0500 Received: from merlin.infradead.org ([205.233.59.134]:50850 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726528AbgBSPF0 (ORCPT ); Wed, 19 Feb 2020 10:05:26 -0500 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; bh=CmpNQkTd3vKnTq7/TH/RtMx5e3zbH2m4y+mEOQjw6BA=; b=1YTSyvj8g/pdWWys4wIaEv5bRJ qJyFJIjYB4oK5I7Iy0dp2rthMCM03ED3LLgk6XlGpU5goYtIqBYawszo4VXN+zS/vHonBsS9RjbZl 9rgiiswz71jqImDv0ysKRU1jeYLEA/NDfJcjym7gT3//6hiskVsHQZarFROJQD1jmOGTZ16p+EwnT mJ+CZwF6A4sO3s3kZRli9MhFHjLNsKJDZBjtlzB9vNXmXrc6HK66RGK+DA3IrpAZuIUF4uYTMy8zj TtvL2T9s+da9RUlqLsEVQv6hJmk5qCJ4YIJ/bsEuaLy+3+GoDSLy8iLbTp6QqaG2j9JHvm4zykXEq p4CKmuAg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1j4QuU-0007V7-IS; Wed, 19 Feb 2020 15:05:10 +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 5D9A1300565; Wed, 19 Feb 2020 16:03:15 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 58B032871C337; Wed, 19 Feb 2020 16:05:07 +0100 (CET) Date: Wed, 19 Feb 2020 16:05:07 +0100 From: Peter Zijlstra To: Steven Rostedt Cc: Andy Lutomirski , Borislav Petkov , Tony Luck , x86-ml , lkml Subject: Re: [RFC] #MC mess Message-ID: <20200219150507.GD18400@hirez.programming.kicks-ass.net> References: <20200218173150.GK14449@zn.tnic> <20200219081541.GG14914@hirez.programming.kicks-ass.net> <20200219092115.3b3cccd9@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200219092115.3b3cccd9@gandalf.local.home> 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 Wed, Feb 19, 2020 at 09:21:15AM -0500, Steven Rostedt wrote: > 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. I don't think that matters much; alternatives should be able to deal with all that either which way around.