From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: [Qemu-devel] [PATCH v2 3/3] X86, mpx: Intel MPX xstate feature definition Date: Fri, 06 Dec 2013 13:33:50 -0800 Message-ID: <52A242BE.3010701@zytor.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: "kvm@vger.kernel.org" , "x86@kernel.org" , Xudong Hao , "qemu-devel@nongnu.org" , "linux-kernel@vger.kernel.org" , Ingo Molnar , Thomas Gleixner To: "Liu, Jinsong" , Paolo Bonzini , "Ren, Qiaowei" Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.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 From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48071) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Vp32P-0001P5-0s for qemu-devel@nongnu.org; Fri, 06 Dec 2013 16:34:25 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Vp32G-0004WW-D5 for qemu-devel@nongnu.org; Fri, 06 Dec 2013 16:34:16 -0500 Received: from terminus.zytor.com ([2001:1868:205::10]:49421 helo=mail.zytor.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Vp32G-0004WC-3o for qemu-devel@nongnu.org; Fri, 06 Dec 2013 16:34:08 -0500 Message-ID: <52A242BE.3010701@zytor.com> Date: Fri, 06 Dec 2013 13:33:50 -0800 From: "H. Peter Anvin" MIME-Version: 1.0 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 3/3] X86, mpx: Intel MPX xstate feature definition List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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" , Thomas Gleixner , Ingo Molnar 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