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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 4F8D1C4332B for ; Mon, 8 Feb 2021 10:44:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F419864E76 for ; Mon, 8 Feb 2021 10:44:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232749AbhBHKnp (ORCPT ); Mon, 8 Feb 2021 05:43:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48630 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232513AbhBHKeZ (ORCPT ); Mon, 8 Feb 2021 05:34:25 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 234EBC061786 for ; Mon, 8 Feb 2021 02:33:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=xDQrJfPpzq6OCLUikNQvBLFdBb366qW2vGqM3YLeABw=; b=tabAUv/VgjwIRD97ABYPW2f3IP 6CN8F7V/rctbyOLPeRO/y+0Jzqx7nmKyBLgls5hk/exbySGeo7DWbsOlFh6pL/GbK98BvuzSb7clw VzpHZQGKTQJEpr9TTExZOnMSCRJvb8RWLzLZaoIZ4fWmP5SC5wgmPBrxWTNZb9Yoa/48Y7YZTGGl5 BxwI91Bxymd7SzMHomkoIMqd7bI7YWjrh2C33HEiUlr0Jg77fRSRqfWnRu6tVx5dy9MZ7lvtxnmj8 j0aJcAD0vjfLa5JMKXTEEKx1N9DAqiMrce1f2RK0ipzxKjP9Cm2bbNewT5jAgsrC2gbrSLeJ8ISzI cbYuaZNA==; 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 1l93rI-0007i5-K1; Mon, 08 Feb 2021 10:33:32 +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 788ED3010D2; Mon, 8 Feb 2021 11:33:30 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 651792BF248D3; Mon, 8 Feb 2021 11:33:30 +0100 (CET) Date: Mon, 8 Feb 2021 11:33:30 +0100 From: Peter Zijlstra To: Andy Lutomirski Cc: Dave Hansen , Borislav Petkov , Linus Torvalds , Steven Rostedt , x86-ml , lkml Subject: Re: [GIT PULL] x86/urgent for v5.11-rc7 Message-ID: References: <661b9809-2c6a-5fc8-163b-a159b84c9ab8@intel.com> <2BFAADF3-EBAA-46D6-B1F6-7A41CB85DA1C@amacapital.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <2BFAADF3-EBAA-46D6-B1F6-7A41CB85DA1C@amacapital.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Feb 07, 2021 at 10:31:32AM -0800, Andy Lutomirski wrote: > > > On Feb 7, 2021, at 10:19 AM, Dave Hansen wrote: > > > > On 2/7/21 9:58 AM, Borislav Petkov wrote: > >>> On Sun, Feb 07, 2021 at 09:49:18AM -0800, Linus Torvalds wrote: > >>> On Sun, Feb 7, 2021 at 2:40 AM Borislav Petkov wrote: > >>>> - Disable CET instrumentation in the kernel so that gcc doesn't add > >>>> ENDBR64 to kernel code and thus confuse tracing. > >>> So this is clearly the right thing to do for now, but I wonder if > >>> people have a plan for actually enabling CET and endbr at cpl0 at some > >>> point? > >> It probably is an item on some Intel manager's to-enable list. So far, > >> the CET enablement concentrates only on userspace but dhansen might know > >> more about future plans. CCed. > > > > It's definitely on our radar to look at after CET userspace. > > > > The only question for me is whether it will be worth doing with the > > exiting kernel entry/exit architecture. > > I assume you mean: is anyone sufficiently inspired to try to handle > NMI correctly? I have a whole pile of nacks saved up for incorrect > implementations, although I will try to wrap them in polite > explanations of precisely what is wrong :) Yeah, the IST stack recursion possibilities are 'fun'. But IIRC CET-SS has far more problems than just NMI. It will also run into all the ROP tricks we pull for return tracing, CALL emulation and other lovely things.