From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:35100) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QYu4f-0003IO-Vy for qemu-devel@nongnu.org; Tue, 21 Jun 2011 02:04:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QYu4e-00037V-HN for qemu-devel@nongnu.org; Tue, 21 Jun 2011 02:04:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:20043) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QYu4d-00037D-Vq for qemu-devel@nongnu.org; Tue, 21 Jun 2011 02:04:32 -0400 Date: Tue, 21 Jun 2011 09:04:28 +0300 From: Gleb Natapov Message-ID: <20110621060428.GC491@redhat.com> References: <1308577094-17551-1-git-send-email-gollub@b1-systems.de> <20110620153825.GH13042@redhat.com> <4DFF6B20.7090107@redhat.com> <201106201826.32975.gollub@b1-systems.de> <4DFF76B1.8020509@redhat.com> <4DFF7FD0.4070002@siemens.com> <4DFF8208.7060401@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4DFF8208.7060401@redhat.com> Subject: Re: [Qemu-devel] [PATCH 0/2] Introduce panic hypercall List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Avi Kivity Cc: Jan Kiszka , Daniel Gollub , qemu-devel , kvm@vger.kernel.org On Mon, Jun 20, 2011 at 08:23:20PM +0300, Avi Kivity wrote: > On 06/20/2011 08:13 PM, Jan Kiszka wrote: > >> A watchdog has the advantage that is also detects lockups. > >> > >> In fact you could implement the panic device via the existing > >> watchdogs. Simply program the timer for the minimum interval and > >> *don't* service the interrupt. This would work for non-virt setups as > >> well as another way to issue a reset. > > > >If you manage to bring down the other guest CPUs fast enough. Otherwise, > >they may corrupt your crashdump before the host had a chance to collect > >all pieces. Synchronous signaling to the hypervisor is a bit safer. > > You could NMI-IPI them. But I agree a synchronous signal is better > (note it's not race-free itself). > But kexec/kdump has exactly same race, so this is at least not worse that alternative. -- Gleb.