From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752523AbdKIGTV (ORCPT ); Thu, 9 Nov 2017 01:19:21 -0500 Received: from mga05.intel.com ([192.55.52.43]:25402 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750743AbdKIGTT (ORCPT ); Thu, 9 Nov 2017 01:19:19 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.44,368,1505804400"; d="scan'208";a="147781200" Date: Wed, 8 Nov 2017 22:17:39 -0800 From: Ricardo Neri To: Paolo Bonzini Cc: Denys Vlasenko , Linus Torvalds , Peter Anvin , Borislav Petkov , Vlastimil Babka , Tony Luck , Fenghua Yu , Josh Poimboeuf , Borislav Petkov , Brian Gerst , Jonathan Corbet , "Ravi V. Shankar" , Chris Metcalf , Andrew Morton , Paul Gortmaker , Masami Hiramatsu , Andrew Lutomirski , Dave Hansen , ray.huang@amd.com, "Michael S. Tsirkin" , Linux Kernel Mailing List , Peter Zijlstra , Chen Yucong , Ingo Molnar , Jiri Slaby , Shuah Khan , Thomas Gleixner , "linux-tip-commits@vger.kernel.org" Subject: Re: [tip:x86/asm] x86/umip: Add emulation code for UMIP instructions Message-ID: <20171109061739.GF30507@voyager> References: <1509935277-22138-8-git-send-email-ricardo.neri-calderon@linux.intel.com> <3cdde8ac-500c-ddad-5ea5-a733e2c98d84@redhat.com> <68c11f7a-cd26-0fdc-0ac5-939a72c22227@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 08, 2017 at 06:14:12PM +0100, Paolo Bonzini wrote: > On 08/11/2017 18:09, Denys Vlasenko wrote: > > On 11/08/2017 05:57 PM, Linus Torvalds wrote: > >> On Wed, Nov 8, 2017 at 8:53 AM, Denys Vlasenko > >> wrote: > >>> We can postpone enabling UMIP by default by a year or so. > >>> By this time, new Wine will be on majority of users' machines. > >> > >> So you are suggesting we run unnecessarily insecure, only in order to > >> not do the emulation that we already have the code for and that the > >> patch implements? > > > > We ran insecure in this way for ~25 years. > > > >> Why? > > > > To avoid having to maintain more obscure, rarely executed code. > > As a start, you could propose a patch to disable the emulation code > through a sysctl or Kconfig symbol. I would be surprised if it takes > more time than what you've spent writing emails in this thread. Indeed, Andy Lutomirski suggested something similar in the past, but as a separate series [1]. Plus, the Wine team was also interested in receiving the SIGSEGV that UMIP would generate, but also acknowledged that it would break existing versions[2]. Thanks and BR, Ricardo [1]. https://lkml.org/lkml/2017/3/8/735 [2]. https://www.winehq.org/pipermail/wine-devel/2016-November/115321.html