From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030850Ab2CNN0F (ORCPT ); Wed, 14 Mar 2012 09:26:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:3817 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756854Ab2CNN0B (ORCPT ); Wed, 14 Mar 2012 09:26:01 -0400 Date: Wed, 14 Mar 2012 15:25:52 +0200 From: Gleb Natapov To: Avi Kivity Cc: Wen Congyang , "Daniel P. Berrange" , kvm list , qemu-devel , "linux-kernel@vger.kernel.org" , KAMEZAWA Hiroyuki , Jan Kiszka , Amit Shah Subject: Re: [PATCH 0/2 v3] kvm: notify host when guest panicked Message-ID: <20120314132552.GC2304@redhat.com> References: <4F606A7C.9090900@cn.fujitsu.com> <4F606DCC.3020908@redhat.com> <4F60726E.3090807@cn.fujitsu.com> <4F607325.6050607@redhat.com> <20120314104608.GU2304@redhat.com> <4F607789.4010109@redhat.com> <4F607CE4.2060809@cn.fujitsu.com> <4F609822.7050502@redhat.com> <20120314131415.GB2304@redhat.com> <4F609A15.5020902@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4F609A15.5020902@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 14, 2012 at 03:16:05PM +0200, Avi Kivity wrote: > On 03/14/2012 03:14 PM, Gleb Natapov wrote: > > On Wed, Mar 14, 2012 at 03:07:46PM +0200, Avi Kivity wrote: > > > On 03/14/2012 01:11 PM, Wen Congyang wrote: > > > > > > > > > > I don't think we want to use the driver. Instead, have a small piece of > > > > > code that resets the device and pushes out a string (the panic message?) > > > > > without any interrupts etc. > > > > > > > > > > It's still going to be less reliable than a hypercall, I agree. > > > > > > > > Do you still want to use complicated and less reliable way? > > > > > > Are you willing to try it out and see how complicated it really is? > > > > > > While it's more complicated, it's also more flexible. You can > > > communicate the panic message, whether the guest is attempting a kdump > > > and its own recovery or whether it wants the host to do it, etc., you > > > can communicate less severe failures like oopses. > > > > > hypercall can take arguments to achieve the same. > > It has to be designed in advance; and every time we notice something's > missing we have to update the host kernel. > We and in the designed stage now. Not to late to design something flexible :) Panic hypercall can take GPA of a buffer where host puts panic info as a parameter. This buffer can be read by QEMU and passed to management. > > > > I think the other ones prefer to touch the hypervisor. > > > > > > I understand the sentiment. Your patches are simple and easy. But my > > > feeling is that the kernel has become too complicated already and I'm > > > looking for ways to limit changes. > > > > > Using virtio-serial will not reduce kernel complexity. Quite contrary > > since code that will use virtio-serial will be more complicated. > > The host kernel is unmodified though. > Yes, this is trade-off between complexity in hypervisor and a guest kernel. But in the end we use the same kernel for both. -- Gleb.