From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:35003) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S2gaU-0005If-PV for qemu-devel@nongnu.org; Wed, 29 Feb 2012 05:16:52 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S2ga7-0001fj-6S for qemu-devel@nongnu.org; Wed, 29 Feb 2012 05:16:46 -0500 Received: from [222.73.24.84] (port=64441 helo=song.cn.fujitsu.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S2ga6-0001f7-Rb for qemu-devel@nongnu.org; Wed, 29 Feb 2012 05:16:23 -0500 Message-ID: <4F4DFB37.8060208@cn.fujitsu.com> Date: Wed, 29 Feb 2012 18:17:27 +0800 From: Wen Congyang MIME-Version: 1.0 References: <4F4AF1FB.6000903@cn.fujitsu.com> <4F4CB926.6050600@redhat.com> <4F4D7F5E.5040202@cn.fujitsu.com> <4F4DF4C6.90609@redhat.com> <20120229095557.GE24600@redhat.com> <4F4DF749.7060507@redhat.com> <20120229100550.GF24600@redhat.com> <4F4DF913.5030809@redhat.com> In-Reply-To: <4F4DF913.5030809@redhat.com> Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1 Subject: Re: [Qemu-devel] [PATCH] kvm: notify host when guest paniced List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Avi Kivity Cc: Gleb Natapov , kvm list , qemu-devel , linux-kernel@vger.kernel.org, KAMEZAWA Hiroyuki At 02/29/2012 06:08 PM, Avi Kivity Wrote: > On 02/29/2012 12:05 PM, Gleb Natapov wrote: >> On Wed, Feb 29, 2012 at 12:00:41PM +0200, Avi Kivity wrote: >>> On 02/29/2012 11:55 AM, Gleb Natapov wrote: >>>>>> >>>>> >>>>> How about using a virtio-serial channel for this? You can transfer any >>>>> amount of information (including the dump itself). >>>>> >>>> Isn't it unreliable after the guest panicked? >>> >>> So is calling hypercalls, or dumping, or writing to the screen. Of >>> course calling a hypercall is simpler and so is more reliable. >>> >> Yes, crash can be so severe that it is not even detected by a kernel >> itself, so not OOPS message even printed. But in most cases if kernel is >> functional enough to print OOPS it is functional enough to call single >> hypercall instruction. > > Why not print the oops to virtio-serial? Or even just a regular serial > port? That's what bare metal does. If virtio-serial's driver has bug or the guest doesn't have such device... > >>>> Having special kdump >>>> kernel that transfers dump to a host via virtio-serial channel though >>>> sounds interesting. May be that's what you mean. >>> >>> Yes. The "panic, starting dump" signal should be initiated by the >>> panicking kernel though, in case the dump fails. >>> >> Then panic hypercall sounds like a reasonable solution. > > It is, but I'm trying to see if we can get away with doing nothing. > If we have a reliable way with doing nothing, it is better. But I donot find such way. Thanks Wen Congyang