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Message-ID: <20120308115656.GD25529@redhat.com>
Date: Thu, 8 Mar 2012 11:56:56 +0000
From: "Daniel P. Berrange" <berrange@...hat.com>
To: Avi Kivity <avi@...hat.com>
Cc: Wen Congyang <wency@...fujitsu.com>,
kvm list <kvm@...r.kernel.org>,
qemu-devel <qemu-devel@...gnu.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Jan Kiszka <jan.kiszka@...mens.com>,
Gleb Natapov <gleb@...hat.com>
Subject: Re: [RESEND][PATCH 2/2 v3] deal with guest panicked event
On Thu, Mar 08, 2012 at 01:52:45PM +0200, Avi Kivity wrote:
> On 03/08/2012 01:36 PM, Daniel P. Berrange wrote:
> > On Thu, Mar 08, 2012 at 01:28:56PM +0200, Avi Kivity wrote:
> > > On 03/08/2012 12:15 PM, Wen Congyang wrote:
> > > > When the host knows the guest is panicked, it will set
> > > > exit_reason to KVM_EXIT_GUEST_PANICKED. So if qemu receive
> > > > this exit_reason, we can send a event to tell management
> > > > application that the guest is panicked and set the guest
> > > > status to RUN_STATE_PANICKED.
> > > >
> > > > Signed-off-by: Wen Congyang <wency@...fujitsu.com>
> > > > ---
> > > > kvm-all.c | 5 +++++
> > > > monitor.c | 3 +++
> > > > monitor.h | 1 +
> > > > qapi-schema.json | 2 +-
> > > > qmp.c | 3 ++-
> > > > vl.c | 1 +
> > > > 6 files changed, 13 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/kvm-all.c b/kvm-all.c
> > > > index 77eadf6..b3c9a83 100644
> > > > --- a/kvm-all.c
> > > > +++ b/kvm-all.c
> > > > @@ -1290,6 +1290,11 @@ int kvm_cpu_exec(CPUState *env)
> > > > (uint64_t)run->hw.hardware_exit_reason);
> > > > ret = -1;
> > > > break;
> > > > + case KVM_EXIT_GUEST_PANICKED:
> > > > + monitor_protocol_event(QEVENT_GUEST_PANICKED, NULL);
> > > > + vm_stop(RUN_STATE_PANICKED);
> > > > + ret = -1;
> > > > + break;
> > > >
> > >
> > > If the management application is not aware of this event, then it will
> > > never resume the guest, so it will appear hung.
> >
> > Even if the mgmt app doesn't know about the QEVENT_GUEST_PANICKED, it should
> > still see a QEVENT_STOP event emitted by vm_stop() surely ? So it will
> > know the guest CPUs have been stopped, even if it isn't aware of the
> > reason why, which seems fine to me.
>
> No. The guest is stopped, and there's no reason to suppose that the
> management app will restart it. Behaviour has changed.
>
> Suppose the guest has reboot_on_panic set; now the behaviour change is
> even more visible - service will stop completely instead of being
> interrupted for a bit while the guest reboots.
Hmm, so this calls for a new command line argument to control behaviour,
similar to what we do for disk werror, eg something like
--onpanic "report|pause|stop|..."
where
report - emit QEVENT_GUEST_PANICKED only
pause - emit QEVENT_GUEST_PANICKED and pause VM
stop - emit QEVENT_GUEST_PANICKED and quit VM
stop - emit QEVENT_GUEST_PANICKED and quit VM
This would map fairly well into libvirt, where we already have config
parameters for controlling what todo with a guest when it panics.
Regards,
Daniel
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