From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755192AbXHVG2e (ORCPT ); Wed, 22 Aug 2007 02:28:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751294AbXHVG21 (ORCPT ); Wed, 22 Aug 2007 02:28:27 -0400 Received: from gw.goop.org ([64.81.55.164]:50807 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750919AbXHVG2Z (ORCPT ); Wed, 22 Aug 2007 02:28:25 -0400 Message-ID: <46CBD78C.3020804@goop.org> Date: Tue, 21 Aug 2007 23:28:28 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.5 (X11/20070719) MIME-Version: 1.0 To: Zachary Amsden CC: Virtualization Mailing List , Linux Kernel Mailing List , Linus Torvalds , Chris Wright , Rusty Russell , Andi Kleen , Andrew Morton , Ben Collins Subject: Re: [PATCH] Fix lazy mode vmalloc synchronization for paravirt References: <46CB91BC.2010808@vmware.com> In-Reply-To: <46CB91BC.2010808@vmware.com> X-Enigmail-Version: 0.95.3 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Zachary Amsden wrote: > Found this looping Ubuntu installs with VMI. > > If unlucky enough to hit a vmalloc sync fault during a lazy mode > operation (from an IRQ handler for a module which was not yet > populated in current page directory, or from inside copy_one_pte, > which touches swap_map, and hit in an unused 4M region), the required > PDE update would never get flushed, causing an infinite page fault loop. Ah, good catch. > This bug affects any paravirt-ops backend which uses lazy updates, I > believe that makes it a bug in Xen, VMI and lguest. It only happens > on LOWMEM kernels. No, under Xen the kernel/hypervisor PMD is not shared between processes, so this is still used when PAE is enabled. J