From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756829Ab2ISR0b (ORCPT ); Wed, 19 Sep 2012 13:26:31 -0400 Received: from terminus.zytor.com ([198.137.202.10]:54156 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756624Ab2ISR03 (ORCPT ); Wed, 19 Sep 2012 13:26:29 -0400 Message-ID: <505A002E.6050304@zytor.com> Date: Wed, 19 Sep 2012 10:26:06 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0 MIME-Version: 1.0 To: Avi Kivity CC: Suresh Siddha , mingo@kernel.org, torvalds@linux-foundation.org, andreas.herrmann3@amd.com, bp@amd64.org, robert.richter@amd.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/6] x86, kvm: use kernel_fpu_begin/end() in kvm_load/put_guest_fpu() References: <1345842782-24175-1-git-send-email-suresh.b.siddha@intel.com> <1345842782-24175-4-git-send-email-suresh.b.siddha@intel.com> <50599AE2.80601@redhat.com> <1348075103.26695.301.camel@sbsiddha-desk.sc.intel.com> <5059FF67.6050005@redhat.com> In-Reply-To: <5059FF67.6050005@redhat.com> X-Enigmail-Version: 1.4.3 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 09/19/2012 10:22 AM, Avi Kivity wrote: > > Note, we could also go in a different direction and make > kernel_fpu_begin() use preempt notifiers and thus make its users > preemptible. But that's for a separate patchset. > Where would you put the state if you were preempted? You want to allocate a full extra buffer for the kernel xstate for each thread just in case? ("Yes" is a valid answer to that question, but it is a fair chunk of memory.) -hpa