From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Olszewski Subject: Shadow MMU state preserved across kvm_mmu_zap_all? Date: Wed, 19 May 2010 22:24:06 -0400 Message-ID: <4BF49D46.5000501@csail.mit.edu> References: <4B9726A7.7000800@csail.mit.edu> <4B976AA8.9030904@redhat.com> <4B9833EE.1070705@csail.mit.edu> <4B989035.4050109@redhat.com> <4B9916DE.30209@csail.mit.edu> <4B9B5225.2050604@redhat.com> <4BA2BC2A.8090803@csail.mit.edu> <4BA33833.8060703@redhat.com> <4BB57596.6090109@csail.mit.edu> <4BB59117.2040903@redhat.com> <4BB614BC.9080608@csail.mit.edu> <4BB8C566.70807@redhat.com> <4BCFDE1C.7080209@csail.mit.edu> <4BCFF241.4080206@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Avi Kivity To: kvm-devel Return-path: Received: from DMZ-MAILSEC-SCANNER-6.MIT.EDU ([18.7.68.35]:42497 "EHLO dmz-mailsec-scanner-6.mit.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751326Ab0ETCYJ (ORCPT ); Wed, 19 May 2010 22:24:09 -0400 In-Reply-To: <4BCFF241.4080206@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Hello, I'm trying to track down a bug I'm observing in a branched version of kvm I'm using for research. I'm hoping someone might be able to point me int to the right direction as I haven't had any luck with it on my own. Here are the details: I have made some changes to kvm that enable guest user applications to use duplicate shadow pages to do interesting things (essentially I duplicate the shadow page table tree for a process multiple times, once for each thread). During my tests, my guest application enables this new feature, completes correctly, and then disables it. Unfortunately, after the test application completes, random programs begin segfaulting for unknown reasons. This is despite the fact that my changes to KVM no longer get executed (verified with a kgdb). At first I thought that I corrupted the shadow pages tables somehow, however, calling kvm_mmu_zap_all does not solve the problem. Thus, I figured I corrupted the guest OS somehow, however, the problem persists even if I reboot the guest OS. So my question is this: Are there any other data structures that survive both a call to kvm_mmu_zap and a guest reboot? Thanks! Marek