From patchwork Thu Oct 31 16:14:04 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 287551 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 7268B2C03DB for ; Fri, 1 Nov 2013 03:12:32 +1100 (EST) Received: from localhost ([::1]:58172 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VburG-00020j-9W for incoming@patchwork.ozlabs.org; Thu, 31 Oct 2013 12:12:30 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51502) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VbuqG-00014C-9u for qemu-devel@nongnu.org; Thu, 31 Oct 2013 12:11:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VbuqA-0004nH-5Q for qemu-devel@nongnu.org; Thu, 31 Oct 2013 12:11:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38919) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Vbuq9-0004ly-RK for qemu-devel@nongnu.org; Thu, 31 Oct 2013 12:11:22 -0400 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r9VGBFYd010315 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Thu, 31 Oct 2013 12:11:16 -0400 Received: from redhat.com (vpn1-5-193.ams2.redhat.com [10.36.5.193]) by int-mx02.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with SMTP id r9VGBAjY005805; Thu, 31 Oct 2013 12:11:11 -0400 Date: Thu, 31 Oct 2013 18:14:04 +0200 From: "Michael S. Tsirkin" To: Paolo Bonzini Message-ID: <20131031161404.GA10710@redhat.com> References: <20131024023903.GD16757@G08FNSTD100614.fnst.cn.fujitsu.com> <20131031143004.GA9948@redhat.com> <52726A0B.4080805@redhat.com> <52726B95.6020006@redhat.com> <20131031145234.GC9948@redhat.com> <52726FAA.6000502@redhat.com> <20131031150955.GE9948@redhat.com> <52727695.8080007@redhat.com> <20131031154556.GB10424@redhat.com> <52727D97.3070209@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <52727D97.3070209@redhat.com> X-Scanned-By: MIMEDefang 2.67 on 10.5.11.12 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: pkrempa@redhat.com, lersek@redhat.com, marcel.a@redhat.com, libvir-list@redhat.com, Hu Tao , qemu-devel@nongnu.org, armbru@redhat.com, rhod@redhat.com, kraxel@redhat.com, anthony@codemonkey.ws, lcapitulino@redhat.com, afaerber@suse.de Subject: Re: [Qemu-devel] pvpanic plans? X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org On Thu, Oct 31, 2013 at 04:56:07PM +0100, Paolo Bonzini wrote: > Il 31/10/2013 16:45, Michael S. Tsirkin ha scritto: > > On Thu, Oct 31, 2013 at 04:26:13PM +0100, Paolo Bonzini wrote: > >> Il 31/10/2013 16:09, Michael S. Tsirkin ha scritto: > >>> On Thu, Oct 31, 2013 at 03:56:42PM +0100, Paolo Bonzini wrote: > >>>> Il 31/10/2013 15:52, Michael S. Tsirkin ha scritto: > >>>>>>> Yes, it does. > >>>>> What does it break exactly? > >>>> > >>>> The point of a panicked event is to examine the guest at a particular > >>>> moment in time (e.g. host-initiated crash dump). If you let the guest > >>>> run, it may reboot and prevent you from getting a meaningful dump. > >>> > >>> Well we trust guest anyway, so I think we can trust it to call halt. > >> > >> No, we cannot. Reboot-in-guest-after-dump-on-host is a perfectly fine > >> configuration. > >> > >>>>>>> But I think that, once we make the pvpanic device is > >>>>>>> optional, to a large extent there is no bug. Adding the pvpanic > >>>>>>> device to the VM will make libvirt obey instead of the > >>>>>>> in-guest setting, and that's it. > >>>>>>> > >>>>>>> Two months have passed and no casualties have been reported due to > >>>>>>> pvpanic. Let's just remove the auto-pvpanic from all machine types in > >>>>>>> 1.7 (yes, that's backwards incompatible in a strict sense), document > >>>>>>> it in the release notes, and hope that the old QEMU versions with > >>>>>>> mandatory pvpanic die of old age. > >>>>> > >>>>> Nod. I'm fine with that. > >>>>> > >>>>> I think we still need to do get rid of the PANICKED state somehow. > >>>>> If we can't replace it with RUNNING state, let's replace it with PAUSED. > >>>>> > >>>>> For example, you can't continue from panicked for some reason. > >>>>> You can't do a reset. But you can pause and then continue. > >>>> > >>>> We need to keep the PANICKED state, but we can make it a normal > >>>> "resumable" state. > >>> > >>> If it's resumable how is it different from PAUSED? > >> > >> If the guest panics while for some reason libvirtd went down, libvirt > >> can see what happened. It is similar to the "I/O error" state in this > >> respect. > >> > >>> Looks like all transitions from paused state should be allowed from panicked > >>> state. So why keep it separate? > >> > >> Because you can poll for the state instead of watching an event. > > > > I see. Maybe it was a mistake to use a separate runtime state for > > this, but oh well. > > Yes, we should have had a list of "reasons" why a guest is stopped (I/O > error, panic, gdb, ...) and a command to clear one or more of them; > there can be paused/running/waiting-for-migration/... states, but many > of the states we have are not necessarily in mutual exclusion. > > But we cannot really choose now. > > > So it should be exactly like paused, we can just find all transitions > > from PAUSED and it should be same for PANICKED? > > Why isn't DEBUG allowed from PAUSED but allowed from PANICKED then? > > Maybe it should be allowed for PAUSED? > > PANICKED->DEBUG was added by commit bc7d0e667. That commit can be > reverted if the panicked state is removed from runstate_needs_reset. > > Paolo Okay so let's drop the code duplication and explicitly make them the same? Signed-off-by: Michael S. Tsirkin diff --git a/vl.c b/vl.c index 46c29c4..e12d317 100644 --- a/vl.c +++ b/vl.c @@ -638,10 +638,6 @@ static const RunStateTransition runstate_transitions_def[] = { { RUN_STATE_WATCHDOG, RUN_STATE_RUNNING }, { RUN_STATE_WATCHDOG, RUN_STATE_FINISH_MIGRATE }, - { RUN_STATE_GUEST_PANICKED, RUN_STATE_PAUSED }, - { RUN_STATE_GUEST_PANICKED, RUN_STATE_FINISH_MIGRATE }, - { RUN_STATE_GUEST_PANICKED, RUN_STATE_DEBUG }, - { RUN_STATE_MAX, RUN_STATE_MAX }, }; @@ -660,6 +656,12 @@ static void runstate_init(void) for (p = &runstate_transitions_def[0]; p->from != RUN_STATE_MAX; p++) { runstate_valid_transitions[p->from][p->to] = true; + /* Panicked state is same as paused, we only made it different so + * management can detect a panic. + */ + if (p->from == RUN_STATE_PAUSED) { + runstate_valid_transitions[RUN_STATE_GUEST_PANICKED][p->to] = true; + } } } @@ -686,8 +688,7 @@ int runstate_is_running(void) bool runstate_needs_reset(void) { return runstate_check(RUN_STATE_INTERNAL_ERROR) || - runstate_check(RUN_STATE_SHUTDOWN) || - runstate_check(RUN_STATE_GUEST_PANICKED); + runstate_check(RUN_STATE_SHUTDOWN); } StatusInfo *qmp_query_status(Error **errp)