From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752734AbYL1UIp (ORCPT ); Sun, 28 Dec 2008 15:08:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752656AbYL1UIe (ORCPT ); Sun, 28 Dec 2008 15:08:34 -0500 Received: from mx2.redhat.com ([66.187.237.31]:43329 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750881AbYL1UIe (ORCPT ); Sun, 28 Dec 2008 15:08:34 -0500 Message-ID: <4957DCC3.3060505@redhat.com> Date: Sun, 28 Dec 2008 22:08:35 +0200 From: Avi Kivity User-Agent: Thunderbird 2.0.0.18 (X11/20081119) MIME-Version: 1.0 To: Andi Kleen , Ingo Molnar CC: x86@kernel.org, linux-kernel , KVM list Subject: Re: [PATCH 0/3] Remove interrupt stack table usage from x86_64 kernel References: <1230238726-17506-1-git-send-email-avi@redhat.com> <87vdt5vfxc.fsf@basil.nowhere.org> <4956A0B1.1060908@redhat.com> <20081227224029.GB496@one.firstfloor.org> <49573FE7.9090802@redhat.com> <20081228131605.GC496@one.firstfloor.org> <49578896.8030703@redhat.com> <20081228190840.GD496@one.firstfloor.org> <4957CE78.6030706@redhat.com> <4957D14B.60805@redhat.com> In-Reply-To: <4957D14B.60805@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Avi Kivity wrote: > Avi Kivity wrote: >> 1. Add per-cpu IDT > > Or we could have just two IDTs - one with IST and one without. I > clocked LIDT at 58 cycles (and we need two per heavyweight switch), so > it's not that wonderful. This makes the whole thing unworthwhile. The vmload/vmsave pair costs only 200 cycles (I should have started with this), and 120 cycles on the heavyweight path plus complexity are not worth 200 cycles on the lightweight path. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.