From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758755Ab3LFVeO (ORCPT ); Fri, 6 Dec 2013 16:34:14 -0500 Received: from terminus.zytor.com ([198.137.202.10]:32946 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752511Ab3LFVeM (ORCPT ); Fri, 6 Dec 2013 16:34:12 -0500 Message-ID: <52A242BE.3010701@zytor.com> Date: Fri, 06 Dec 2013 13:33:50 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: "Liu, Jinsong" , Paolo Bonzini , "Ren, Qiaowei" CC: "kvm@vger.kernel.org" , "x86@kernel.org" , Xudong Hao , "qemu-devel@nongnu.org" , "linux-kernel@vger.kernel.org" , Ingo Molnar , Thomas Gleixner Subject: Re: [Qemu-devel] [PATCH v2 3/3] X86, mpx: Intel MPX xstate feature definition References: <1386375658-2191-1-git-send-email-qiaowei.ren@intel.com> <1386375658-2191-3-git-send-email-qiaowei.ren@intel.com> <52A20AD6.8080706@redhat.com> In-Reply-To: X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/06/2013 12:05 PM, Liu, Jinsong wrote: >> >> Since Peter already said the same, please undo these changes. >> >> Also, how is XSTATE_EAGER used? Should MPX be disabled when xsaveopt >> is disabled on the kernel command line? (Liu, how would this affect >> the KVM patches, too?) >> >> Paolo > > Currently seems no, and if needed we can add a new patch at kvm side accordingly when native mpx patches checked in. > We need to either disable these features in lazy mode, or we need to force eager mode if these features are to be supported. The problem with the latter is that it means forcing eager mode regardless of if anything actually *uses* these features. A third option would be to require applications to use a prctl() or similar to enable eager-save features. Thoughts? -hpa