From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753449Ab2DROGZ (ORCPT ); Wed, 18 Apr 2012 10:06:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:30431 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753174Ab2DROGT (ORCPT ); Wed, 18 Apr 2012 10:06:19 -0400 Message-ID: <4F8ECA4F.7070305@redhat.com> Date: Wed, 18 Apr 2012 17:06:07 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120329 Thunderbird/11.0.1 MIME-Version: 1.0 To: "Nadav Har'El" CC: Anthony Liguori , kvm@vger.kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/4] Export offsets of VMCS fields as note information for kdump References: <4F84E0DF.8040206@cn.fujitsu.com> <4F8D1F46.3090901@redhat.com> <4F8D9F20.9050507@codemonkey.ws> <4F8EAFF7.2040505@redhat.com> <20120418134743.GA25786@fermat.math.technion.ac.il> In-Reply-To: <20120418134743.GA25786@fermat.math.technion.ac.il> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/18/2012 04:47 PM, Nadav Har'El wrote: > On Wed, Apr 18, 2012, Avi Kivity wrote about "Re: [PATCH 0/4] Export offsets of VMCS fields as note information for kdump": > > Right; they're also not required to be in memory at all - the processor > > can cache them, even for VMCSs that are not active at this time. > > Running VMXOFF at panic time can fix that, but you have to broadcast it > > to all processors, probably using NMI... > > I believe that a VMCLEAR ensures that the VMCS is written back to > memory. KVM uses this fact when migrating a VMCS between two separate > physical CPUs - it runs VMCLEAR on the old CPU, to write the VMCS to > memory, and then VMPTRLD on the new CPU. > > So you don't need to VMXOFF, but do need to VMCLEAR. But there's still > the complication that you mention - you need to do the VMCLEAR on the right > processor... VMCLEAR only clears one VMCS; several may be cached by a processor at one time. Presumably VMXOFF flushes everything. -- error compiling committee.c: too many arguments to function