From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937717AbdCJOSu (ORCPT ); Fri, 10 Mar 2017 09:18:50 -0500 Received: from mail-ua0-f169.google.com ([209.85.217.169]:36016 "EHLO mail-ua0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935224AbdCJOSp (ORCPT ); Fri, 10 Mar 2017 09:18:45 -0500 MIME-Version: 1.0 In-Reply-To: <63231222-5b42-c8c9-02f0-0afbe702d8b5@list.ru> References: <20170308003254.27833-1-ricardo.neri-calderon@linux.intel.com> <79ba0fff-4c01-2bfa-06cb-5cfc98dd710c@list.ru> <997ba581-ecfa-b773-a48e-85b92a439836@list.ru> <1489022122.131264.33.camel@ranerica-desktop> <63231222-5b42-c8c9-02f0-0afbe702d8b5@list.ru> From: Andy Lutomirski Date: Fri, 10 Mar 2017 06:17:45 -0800 Message-ID: Subject: Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention To: Stas Sergeev Cc: Ricardo Neri , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Andy Lutomirski , Borislav Petkov , Peter Zijlstra , Andrew Morton , Brian Gerst , Chris Metcalf , Dave Hansen , Paolo Bonzini , Liang Z Li , Masami Hiramatsu , Huang Rui , Jiri Slaby , Jonathan Corbet , "Michael S. Tsirkin" , Paul Gortmaker , Vlastimil Babka , Chen Yucong , Alexandre Julliard , Fenghua Yu , "Ravi V. Shankar" , Shuah Khan , "linux-kernel@vger.kernel.org" , X86 ML , linux-msdos@vger.kernel.org, wine-devel@winehq.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id v2AEIwps027722 On Fri, Mar 10, 2017 at 3:33 AM, Stas Sergeev wrote: > 10.03.2017 05:39, Andy Lutomirski пишет: > >> On Thu, Mar 9, 2017 at 2:10 PM, Stas Sergeev wrote: >>> >>> 09.03.2017 04:15, Ricardo Neri пишет: >>> >>>> On Wed, 2017-03-08 at 08:46 -0800, Andy Lutomirski wrote: >>>>> >>>>> On Wed, Mar 8, 2017 at 8:29 AM, Stas Sergeev wrote: >>>>>> >>>>>> 08.03.2017 19:06, Andy Lutomirski пишет: >>>>>>> >>>>>>> On Wed, Mar 8, 2017 at 6:08 AM, Stas Sergeev wrote: >>>>>>>> >>>>>>>> 08.03.2017 03:32, Ricardo Neri пишет: >>>>>>>>> >>>>>>>>> These are the instructions covered by UMIP: >>>>>>>>> * SGDT - Store Global Descriptor Table >>>>>>>>> * SIDT - Store Interrupt Descriptor Table >>>>>>>>> * SLDT - Store Local Descriptor Table >>>>>>>>> * SMSW - Store Machine Status Word >>>>>>>>> * STR - Store Task Register >>>>>>>>> >>>>>>>>> This patchset initially treated tasks running in virtual-8086 >>>>> >>>>> mode as a >>>>>>>>> >>>>>>>>> special case. However, I received clarification that DOSEMU[8] >>>>> >>>>> does not >>>>>>>>> >>>>>>>>> support applications that use these instructions. >>>>>>> >>>>>>> Can you remind me what was special about it? It looks like you >>>>> >>>>> still >>>>>>> >>>>>>> emulate them in v8086 mode. >>>>>> >>>>>> Indeed, sorry, I meant prot mode here. :) >>>>>> So I wonder what was cited to be special about v86. >>>> >>>> Initially my patches disabled UMIP on virtual-8086 instructions, without >>>> regards of protected mode (i.e., UMIP was always enabled). I didn't have >>>> emulation at the time. Then, I added emulation code that now covers >>>> protected and virtual-8086 modes. I guess it is not special anymore. >>> >>> But isn't SLDT&friends just throw UD in v86? >>> How does UMIP affect this? How does your patch affect >>> this? >> >> Er, right. Ricardo, your code may need fixing. But don't you have a >> test case for this? > > Why would you need one? > Or do you really want to allow these instructions > in v86 by the means of emulation? If so - this wasn't > clearly stated in the patch description, neither it was > properly discussed, it seems. What I meant was: if the patches incorrectly started making these instructions work in vm86 mode where they used to cause a vm86 exit, then that's a bug that the selftest should have caught.