From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 0/30] nVMX: Nested VMX, v9 Date: Mon, 23 May 2011 18:19:54 +0300 Message-ID: <4DDA7B1A.7060403@redhat.com> References: <20110512163115.GA13138@fermat.math.technion.ac.il> <20110512165157.GC20193@redhat.com> <20110522193239.GA13130@fermat.math.technion.ac.il> <4DDA2E72.8070907@redhat.com> <20110523130226.GC23407@8bytes.org> <4DDA5C30.10107@redhat.com> <20110523134052.GD23407@8bytes.org> <4DDA66AF.7020505@redhat.com> <20110523142846.GE23407@8bytes.org> <4DDA706C.1000200@redhat.com> <20110523145855.GF23407@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "Nadav Har'El" , Gleb Natapov , kvm@vger.kernel.org, abelg@il.ibm.com To: Joerg Roedel Return-path: Received: from mx1.redhat.com ([209.132.183.28]:64463 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752758Ab1EWPUF (ORCPT ); Mon, 23 May 2011 11:20:05 -0400 In-Reply-To: <20110523145855.GF23407@8bytes.org> Sender: kvm-owner@vger.kernel.org List-ID: On 05/23/2011 05:58 PM, Joerg Roedel wrote: > On Mon, May 23, 2011 at 05:34:20PM +0300, Avi Kivity wrote: > > On 05/23/2011 05:28 PM, Joerg Roedel wrote: > > >> To user-space we can provide a VCPU_FREEZE/VCPU_UNFREEZE ioctl which > >> does all the necessary things. > > > > Or we can automatically flush things on any exit to userspace. They > > should be very rare in guest mode. > > This would make nesting mostly transparent to migration, so it sounds > good in this regard. > > I do not completly agree that user-space exits in guest-mode are rare, > this depends on the hypervisor in the L1. In Hyper-V for example the > root-domain uses hardware virtualization too and has direct access to > devices (at least to some degree). IOIO is not intercepted in the > root-domain, for example. Not sure about the MMIO regions. Good point. We were also talking about passing through virtio (or even host) devices to the guest. So an ioctl to flush volatile state to memory would be a good idea. -- error compiling committee.c: too many arguments to function