From mboxrd@z Thu Jan 1 00:00:00 1970 From: Muli Ben-Yehuda Subject: Re: [PATCH 1/7] Nested VMX patch 1 implements vmon and vmoff Date: Mon, 21 Dec 2009 17:52:06 +0200 Message-ID: <20091221155206.GE2500@il.ibm.com> References: <1260470309-7166-1-git-send-email-oritw@il.ibm.com> <1260470309-7166-2-git-send-email-oritw@il.ibm.com> <20091220142018.GI4490@redhat.com> <87eimpefpn.fsf@basil.nowhere.org> <4B2E7551.6050201@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andi Kleen , Gleb Natapov , Orit Wasserman , kvm@vger.kernel.org, Ben-Ami Yassour1 , Abel Gordon , aliguori@us.ibm.com, mdday@us.ibm.com To: Avi Kivity Return-path: Received: from mtagate1.uk.ibm.com ([194.196.100.161]:34747 "EHLO mtagate1.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756107AbZLUPwJ (ORCPT ); Mon, 21 Dec 2009 10:52:09 -0500 Received: from d06nrmr1806.portsmouth.uk.ibm.com (d06nrmr1806.portsmouth.uk.ibm.com [9.149.39.193]) by mtagate1.uk.ibm.com (8.13.1/8.13.1) with ESMTP id nBLFq8YP023180 for ; Mon, 21 Dec 2009 15:52:08 GMT Received: from d06av01.portsmouth.uk.ibm.com (d06av01.portsmouth.uk.ibm.com [9.149.37.212]) by d06nrmr1806.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id nBLFq8UU1351732 for ; Mon, 21 Dec 2009 15:52:08 GMT Received: from d06av01.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av01.portsmouth.uk.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id nBLFq74H012543 for ; Mon, 21 Dec 2009 15:52:08 GMT Content-Disposition: inline In-Reply-To: <4B2E7551.6050201@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Sun, Dec 20, 2009 at 09:04:49PM +0200, Avi Kivity wrote: > >Since VMX was not originally designed to be nested that wouldn't > >surprise me. > > vmx was designed to correct the non-virtualizability of x86. It > would have been criminal to design it without nesting in mind, > especially given all the prior art. > > vmx does support nesting, albeit not very efficiently. I would say that VMX only supports nesting if you define "supports" as "does not make it impossible". The fact that VMX operations in executed in non-root mode are trapped is welcome, but there's so much more that could be done in hardware to make nesting "better supported" that I would hesitate to say that the current generation of VMX supports nesting. Cheers, Muli -- Muli Ben-Yehuda | muli@il.ibm.com | +972-4-8281080 Manager, Virtualization and Systems Architecture Master Inventor, IBM Research -- Haifa Second Workshop on I/O Virtualization (WIOV '10): http://sysrun.haifa.il.ibm.com/hrl/wiov2010/