From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755518AbYIRWSh (ORCPT ); Thu, 18 Sep 2008 18:18:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757257AbYIRWS0 (ORCPT ); Thu, 18 Sep 2008 18:18:26 -0400 Received: from gw.goop.org ([64.81.55.164]:46543 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755161AbYIRWSZ (ORCPT ); Thu, 18 Sep 2008 18:18:25 -0400 Message-ID: <48D2D3B2.10503@goop.org> Date: Thu, 18 Sep 2008 15:18:26 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.16 (X11/20080723) MIME-Version: 1.0 To: Avi Kivity CC: Nick Piggin , Hugh Dickens , Linux Memory Management List , Linux Kernel Mailing List , Avi Kivity , Andrew Morton , Rik van Riel , Marcelo Tosatti Subject: Re: Populating multiple ptes at fault time References: <48D142B2.3040607@goop.org> <48D17E75.80807@redhat.com> <48D1851B.70703@goop.org> <48D18919.9060808@redhat.com> <48D18C6B.5010407@goop.org> <48D2B970.7040903@redhat.com> In-Reply-To: <48D2B970.7040903@redhat.com> X-Enigmail-Version: 0.95.7 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 Avi Kivity wrote: >> Do you need to set the A bit synchronously? > > Yes, of course (if no guest cooperation). Is the A bit architecturally guaranteed to be synchronously set? Can speculative accesses set it? SDM vol 3 is a bit vague about it. > I'll fail my own unit tests. > > If we add an async mode for guests that can cope, maybe this is > workable. I guess this is what you're suggesting. > Yes. At worst Linux would underestimate the process RSS a bit (depending on how many unsynchronized ptes you leave lying around). I bet there's an appropriate pvop hook you could use to force synchronization just before the kernel actually inspects the bits (leaving lazy mode sounds good). J