From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 0/24] Nested VMX, v5 Date: Sun, 11 Jul 2010 16:12:10 +0300 Message-ID: <4C39C32A.5000403@redhat.com> References: <1276431753-nyh@il.ibm.com> <1A42CE6F5F474C41B63392A5F80372B21F70B7B1@shsmsx501.ccr.corp.intel.com> <20100711082703.GA37@fermat.math.technion.ac.il> <1FEA66BE-8BFC-4158-A0F1-CDD8E595D0D7@suse.de> <20100711124937.GA11157@fermat.math.technion.ac.il> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Alexander Graf , "Dong, Eddie" , "kvm@vger.kernel.org" To: "Nadav Har'El" Return-path: Received: from mx1.redhat.com ([209.132.183.28]:12414 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752997Ab0GKNMV (ORCPT ); Sun, 11 Jul 2010 09:12:21 -0400 In-Reply-To: <20100711124937.GA11157@fermat.math.technion.ac.il> Sender: kvm-owner@vger.kernel.org List-ID: On 07/11/2010 03:49 PM, Nadav Har'El wrote: > > In any case, the obvious problem with this whole idea on VMX is that it > requires a modified guest hypervisor, which reduces its usefulness. > This is why we didn't think we should "advertise" the ability to bypass > vmread/vmwrite in L1 and write directly to the vmcs12's. But Avi Kivity > already asked me to add a document about the vmcs12 internal structure, > and once I've done that, I guess you can now consider it "fair" for nesting- > aware L1 guest hypervisors to actually use that internal structure to modify > vmcs12 directly, without vmread/vmwrite and exits. > No, they can't, since (for writes) L0 might cache the information and not read it again. For reads, L0 might choose to update vmcs12 on demand. A pvvmread/write needs to communicate with L0 about what fields are valid (likely using available and dirty bitmaps). -- error compiling committee.c: too many arguments to function