From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:40427) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SAQpx-0007Or-4f for qemu-devel@nongnu.org; Wed, 21 Mar 2012 15:04:47 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SAQpq-0003Qx-Ph for qemu-devel@nongnu.org; Wed, 21 Mar 2012 15:04:44 -0400 Received: from mail-ob0-f173.google.com ([209.85.214.173]:63588) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SAQpq-0003Qn-KG for qemu-devel@nongnu.org; Wed, 21 Mar 2012 15:04:38 -0400 Received: by obbwd20 with SMTP id wd20so998269obb.4 for ; Wed, 21 Mar 2012 12:04:37 -0700 (PDT) Message-ID: <4F6A2642.1060107@redhat.com> Date: Wed, 21 Mar 2012 14:04:34 -0500 From: Anthony Liguori MIME-Version: 1.0 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 Subject: Re: [Qemu-devel] [PATCH 0/2 v3] kvm: notify host when guest panicked List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Avi Kivity Cc: kvm list , Gleb Natapov , Jan Kiszka , "linux-kernel@vger.kernel.org" , qemu-devel , KAMEZAWA Hiroyuki 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 >