From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]) by merlin.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1TNmpZ-00031j-8Q for kexec@lists.infradead.org; Mon, 15 Oct 2012 15:43:50 +0000 Message-ID: <507C2F18.8080904@redhat.com> Date: Mon, 15 Oct 2012 17:43:20 +0200 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [PATCH 0/3] x86: clear vmcss on all cpus when doing kdump if necessary References: <5077BB7B.4030203@cn.fujitsu.com> In-Reply-To: <5077BB7B.4030203@cn.fujitsu.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: kexec-bounces@lists.infradead.org Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Zhang Yanfei Cc: x86@kernel.org, "kvm@vger.kernel.org" , linux-doc@vger.kernel.org, mtosatti@redhat.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org On 10/12/2012 08:40 AM, Zhang Yanfei wrote: > Currently, kdump just makes all the logical processors leave VMX operation by > executing VMXOFF instruction, so any VMCSs active on the logical processors may > be corrupted. But, sometimes, we need the VMCSs to debug guest images contained > in the host vmcore. To prevent the corruption, we should VMCLEAR the VMCSs before > executing the VMXOFF instruction. How have you verified that VMXOFF doesn't flush cached VMCSs already? > > The patch set provides an alternative way to clear VMCSs related to guests > on all cpus when host is doing kdump. > I'm not sure the sysctl is really necessary. The only reason to turn if off is if the corruption is so severe that the loaded vmcs list itself causes a crash. I think it should be rare enough that we can do it unconditionally. -- error compiling committee.c: too many arguments to function _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 0/3] x86: clear vmcss on all cpus when doing kdump if necessary Date: Mon, 15 Oct 2012 17:43:20 +0200 Message-ID: <507C2F18.8080904@redhat.com> References: <5077BB7B.4030203@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, "kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, mtosatti-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Zhang Yanfei Return-path: In-Reply-To: <5077BB7B.4030203-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kexec-bounces-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org Errors-To: kexec-bounces+glkk-kexec=m.gmane.org-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: kvm.vger.kernel.org On 10/12/2012 08:40 AM, Zhang Yanfei wrote: > Currently, kdump just makes all the logical processors leave VMX operation by > executing VMXOFF instruction, so any VMCSs active on the logical processors may > be corrupted. But, sometimes, we need the VMCSs to debug guest images contained > in the host vmcore. To prevent the corruption, we should VMCLEAR the VMCSs before > executing the VMXOFF instruction. How have you verified that VMXOFF doesn't flush cached VMCSs already? > > The patch set provides an alternative way to clear VMCSs related to guests > on all cpus when host is doing kdump. > I'm not sure the sysctl is really necessary. The only reason to turn if off is if the corruption is so severe that the loaded vmcs list itself causes a crash. I think it should be rare enough that we can do it unconditionally. -- error compiling committee.c: too many arguments to function From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752936Ab2JOPnx (ORCPT ); Mon, 15 Oct 2012 11:43:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:16777 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752480Ab2JOPnu (ORCPT ); Mon, 15 Oct 2012 11:43:50 -0400 Message-ID: <507C2F18.8080904@redhat.com> Date: Mon, 15 Oct 2012 17:43:20 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120911 Thunderbird/15.0.1 MIME-Version: 1.0 To: Zhang Yanfei CC: x86@kernel.org, kexec@lists.infradead.org, linux-doc@vger.kernel.org, mtosatti@redhat.com, linux-kernel@vger.kernel.org, "kvm@vger.kernel.org" Subject: Re: [PATCH 0/3] x86: clear vmcss on all cpus when doing kdump if necessary References: <5077BB7B.4030203@cn.fujitsu.com> In-Reply-To: <5077BB7B.4030203@cn.fujitsu.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/12/2012 08:40 AM, Zhang Yanfei wrote: > Currently, kdump just makes all the logical processors leave VMX operation by > executing VMXOFF instruction, so any VMCSs active on the logical processors may > be corrupted. But, sometimes, we need the VMCSs to debug guest images contained > in the host vmcore. To prevent the corruption, we should VMCLEAR the VMCSs before > executing the VMXOFF instruction. How have you verified that VMXOFF doesn't flush cached VMCSs already? > > The patch set provides an alternative way to clear VMCSs related to guests > on all cpus when host is doing kdump. > I'm not sure the sysctl is really necessary. The only reason to turn if off is if the corruption is so severe that the loaded vmcs list itself causes a crash. I think it should be rare enough that we can do it unconditionally. -- error compiling committee.c: too many arguments to function