From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: Plan 9 install problems Date: Sat, 16 Dec 2006 09:58:21 +0200 Message-ID: <4583A71D.50300@qumranet.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Return-path: To: James Morris In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org James Morris wrote: > I just tried installing Plan 9 from the current CD ISO (see > http://plan9.bell-labs.com/plan9/download.html) under KVM and didn't get > very far. > > It boots, then hangs after some initialization. Screenshot of the guest > at this point: http://namei.org/images/p9-kvm.png > > On the host, the startup messages look like: > > set_vram_mapping: memory: e0000000 - e0800000 > set_vram_mapping: return 0x2b03ced87000 > vga_update_vram: base 0x2b03ced87000 ptr 0x2b03ce585010 > vga_update_vram: done > > kernel: kvm: unhandled rdmsr: 1 > > This is an old Penium msr related to machine checks. > When the guest hangs, the host starts logging this repeatedly: > > kernel: double fault 0x80031b30 @ 0xf01003c9 > Since we don't handle the rdmsr, we inject a general protection fault. The guest isn't ready to handle this, so we inject a double fault. The guest isn't ready to handle a double fault either -- at this point we should triple fault but we don't. > This is with the 2.6.20-rc1 kernel and kvm-6 userland. > > Seems to work as expected with the kvm kernel module unloaded (i.e. plain > qemu). > The way to fix is to add handling to {svm,vmx}_get_msr() for msr 1 (and any other pointless msrs the guest reads or writes). From a cursory reading of the machine check docs, returning 0 should be fine for msr 1. [those common msrs should really be moved to kvm_main.c one day] -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV