From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756310Ab2CUTEj (ORCPT ); Wed, 21 Mar 2012 15:04:39 -0400 Received: from mail-yx0-f174.google.com ([209.85.213.174]:45253 "EHLO mail-yx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751054Ab2CUTEh (ORCPT ); Wed, 21 Mar 2012 15:04:37 -0400 Message-ID: <4F6A2642.1060107@redhat.com> Date: Wed, 21 Mar 2012 14:04:34 -0500 From: Anthony Liguori User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.2) Gecko/20120216 Thunderbird/10.0.2 MIME-Version: 1.0 To: Avi Kivity CC: "Daniel P. Berrange" , kvm list , Jan Kiszka , "linux-kernel@vger.kernel.org" , Gleb Natapov , qemu-devel , KAMEZAWA Hiroyuki Subject: Re: [Qemu-devel] [PATCH 0/2 v3] kvm: notify host when guest panicked References: <4F58664D.1070800@cn.fujitsu.com> <4F58943E.1050402@redhat.com> <4F595B31.9090301@cn.fujitsu.com> <4F5DBC26.7060204@cn.fujitsu.com> <4F5DD0FD.9070904@redhat.com> <20120313091843.GB3800@redhat.com> <4F5F25BF.7060100@redhat.com> In-Reply-To: <4F5F25BF.7060100@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/13/2012 05:47 AM, Avi Kivity wrote: > On 03/13/2012 11:18 AM, Daniel P. Berrange wrote: >> On Mon, Mar 12, 2012 at 12:33:33PM +0200, Avi Kivity wrote: >>> On 03/12/2012 11:04 AM, Wen Congyang wrote: >>>> Do you have any other comments about this patch? >>>> >>> >>> Not really, but I'm not 100% convinced the patch is worthwhile. It's >>> likely to only be used by Linux, which has kexec facilities, and you can >>> put talk to management via virtio-serial and describe the crash in more >>> details than a simple hypercall. >> >> As mentioned before, I don't think virtio-serial is a good fit for this. >> We want something that is simple& guaranteed always available. Using >> virtio-serial requires significant setup work on both the host and guest. > > So what? It needs to be done anyway for the guest agent. > >> Many management application won't know to make a vioserial device available >> to all guests they create. > > Then they won't know to deal with the panic event either. > >> Most administrators won't even configure kexec, >> let alone virtio serial on top of it. > > It should be done by the OS vendor, not the individual admin. > >> The hypercall requires zero host >> side config, and zero guest side config, which IMHO is what we need for >> this feature. > > If it was this one feature, yes. But we keep getting more and more > features like that and we bloat the hypervisor. There's a reason we > have a host-to-guest channel, we should use it. The problem is that virtio-serial sucks for something like this. We have two options I think: 1) We could reserve a portion of the hypercall space to be deferred to userspace for stuff like this. 2) We could invent a new hypercall like facility that was less bloated than virtio-serial for stuff like this using MMIO/PIO. Regards, Anthony Liguori >