Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754477AbdCJCkI (ORCPT ); Thu, 9 Mar 2017 21:40:08 -0500 Received: from mail-ua0-f182.google.com ([209.85.217.182]:36484 "EHLO mail-ua0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753524AbdCJCkG (ORCPT ); Thu, 9 Mar 2017 21:40:06 -0500 MIME-Version: 1.0 In-Reply-To: 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> From: Andy Lutomirski Date: Thu, 9 Mar 2017 18:39:38 -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 v2A2eDPM026864 Content-Length: 1892 Lines: 54 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? The behavior should be the same with and without your patches applied. The exception is #UD, not #GP, so maybe your code just never executes in the vm86 case. --Andy