From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:43213) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S2gSr-0001x1-Ce for qemu-devel@nongnu.org; Wed, 29 Feb 2012 05:08:57 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S2gSR-0008Ch-JN for qemu-devel@nongnu.org; Wed, 29 Feb 2012 05:08:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:3697) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S2gSR-0008C8-BR for qemu-devel@nongnu.org; Wed, 29 Feb 2012 05:08:27 -0500 Message-ID: <4F4DF913.5030809@redhat.com> Date: Wed, 29 Feb 2012 12:08:19 +0200 From: Avi Kivity 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> In-Reply-To: <20120229100550.GF24600@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] kvm: notify host when guest paniced List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gleb Natapov Cc: kvm list , qemu-devel , linux-kernel@vger.kernel.org, KAMEZAWA Hiroyuki 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. > > > 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. -- error compiling committee.c: too many arguments to function