From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: KVM & VMX root mode Date: Sat, 01 Sep 2007 18:59:15 +0300 Message-ID: <46D98C53.4070604@qumranet.com> References: <46D81156.8050100@innotek.de> <46D97669.7050609@qumranet.com> <46D980C2.3040501@innotek.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Sander van Leeuwen Return-path: In-Reply-To: <46D980C2.3040501-2taLTamkYL2ELgA04lAiVw@public.gmane.org> 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 Sander van Leeuwen wrote: > Hi Avi, > > Our non-vmx mode fails, because the cpu is in vmx root mode. > > Two products that use vt-x for virtualization could perfectly co-exist > if both comply with the way Intel recommends people to use vt-x. > See figure 19.1 in chapter 19.4 of the 'Intel 64 and IA-32 > Architectures Software Developer's Manual'. VirtualBox is programmed to > follow these rules and therefor allows any other virtualizer to run > side-by-side. As far as I understand, kvm follows these rules. It enables vmx when loaded and disables then when unloaded. > > Currently KVM prevents us from using our generic virtualization engine > and does not allow anybody else to use the vt-x extensions (without > explicitely leaving vmx root mode). Well, obviously kvm can't operate if you disable cr4.vmxe and/or switch paging off. The two solutions are not run-time compatible. I don't see why this is a problem as you should simply not run the product you aren't using, and everything should just work. > > As your product is included in the mainline Linux kernel and enabled > by default, it would be nice if you could follow Intel's recommendations. kvm isn't enabled by default. It requires explicit user action to enter vmx mode ('modprobe kvm-intel'). -- Any sufficiently difficult bug is indistinguishable from a feature. ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/