Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1752547AbcKIE0H (ORCPT <rfc822;w@1wt.eu>);
        Tue, 8 Nov 2016 23:26:07 -0500
Received: from mga07.intel.com ([134.134.136.100]:33644 "EHLO mga07.intel.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1751647AbcKIE0E (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 8 Nov 2016 23:26:04 -0500
X-ExtLoop1: 1
X-IronPort-AV: E=Sophos;i="5.31,612,1473145200"; 
   d="scan'208";a="189291404"
Message-ID: <1478665563.2533.3.camel@ranerica-desktop>
Subject: Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention
From: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@amacapital.net>,
        Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        X86 ML <x86@kernel.org>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Borislav Petkov <bp@suse.de>, Brian Gerst <brgerst@gmail.com>,
        Chen Yucong <slaoub@gmail.com>, Chris Metcalf <cmetcalf@mellanox.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Fenghua Yu <fenghua.yu@intel.com>, Huang Rui <ray.huang@amd.com>,
        Jiri Slaby <jslaby@suse.cz>, Jonathan Corbet <corbet@lwn.net>,
        "Michael S . Tsirkin" <mst@redhat.com>,
        Paul Gortmaker <paul.gortmaker@windriver.com>,
        "Ravi V . Shankar" <ravi.v.shankar@intel.com>,
        Vlastimil Babka <vbabka@suse.cz>, Shuah Khan <shuah@kernel.org>
Date: Tue, 08 Nov 2016 20:26:03 -0800
In-Reply-To: <alpine.DEB.2.20.1611081750360.3501@nanos>
References: <1478585533-19406-1-git-send-email-ricardo.neri-calderon@linux.intel.com>
         <20161108131600.GF3117@twins.programming.kicks-ass.net>
         <CALCETrV+c4Rw9zbB3=Jc2F6jtxib3prxNqMXgnUSyMc5QnU9fA@mail.gmail.com>
         <alpine.DEB.2.20.1611081750360.3501@nanos>
Content-Type: text/plain; charset="UTF-8"
X-Mailer: Evolution 3.10.4-0ubuntu2 
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 1179
Lines: 27

On Tue, 2016-11-08 at 17:52 +0100, Thomas Gleixner wrote:
> On Tue, 8 Nov 2016, Andy Lutomirski wrote:
> > On Tue, Nov 8, 2016 at 5:16 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> > > On Mon, Nov 07, 2016 at 10:12:09PM -0800, Ricardo Neri wrote:
> > >> There is a caveat, however. Certain applications running in virtual-8086
> > >> mode, such as DOSEMU[1] and Wine[2], want to utilize the SGDT, SIDT and
> > >> SLDT instructions for legitimate reasons. In order to keep such
> > >> applications working, UMIP must be disabled/enabled when entering/exiting
> > >> virtual-8086 mode.
> > >
> > > Would it not be better to emulate these instructions for them? What way
> > > we can verify they're not malicious.
> > 
> > Forget malice -- if they are really needed for some silly vm86-using
> > program, let's trap them and emulate them so they return dummy values.
> 
> handle_vm86_fault() already does instruction emulation, so adding the few
> bits there is the right thing to do. Then we just can enable UMIP
> unconditionally and be done with it.

Ah. I didn't think about that. It make sense to me. I will rework this
series with this approach.
> 
> Thanks,
> 
> 	tglx