Re: [KVMTOOL][PATCH] Handle KVM_EXIT_SYSTEM_EVENT on any VCPU

[Mark Rutland <mark.rutland@arm.com>]

On Thu, Sep 03, 2015 at 11:24:29AM +0100, Suzuki Poulose wrote:
> On Wed, Sep 2, 2015 at 11:50 AM, Mark Rutland <mark.rutland@arm.com> wrote:
> >
> > When VCPU #0 exits (e.g. due to KVM_EXIT_SYSTEM_EVENT), it sends
> > SIGKVMEXIT to all other VCPUs, waits for them to exit, then tears down
> > any remaining context. The signalling of SIGKVMEXIT is critical to
> > forcing VCPUs to shut down in response to a system event (e.g. PSCI
> > SYSTEM_OFF).
> >
> > VCPUs other that VCPU #0 simply exit in kvm_cpu_thread without forcing
> > other CPUs to shut down. Thus if a system event is taken on a VCPU other
> > than VCPU #0, the remaining CPUs are left online. This results in KVM
> > tool not exiting as expected when a system event is taken on a VCPU
> > other than VCPU #0 (as may happen if the guest panics).
> >
> > Fix this by signalling SIGKVMEXIT to VCPU #0 when a system event is
> > taken on other CPUs, so that it may tear things down as usual.
> >
> > Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> > Cc: Will Deacon <will.deacon@arm.com>
> > Cc: Marc Zyngier <marc.zyngier@arm.com>
> > ---
> >  kvm-cpu.c | 15 +++++++++++----
> >  1 file changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/kvm-cpu.c b/kvm-cpu.c
> > index 5d90664..f47e3db 100644
> > --- a/kvm-cpu.c
> > +++ b/kvm-cpu.c
> > @@ -166,13 +166,20 @@ int kvm_cpu__start(struct kvm_cpu *cpu)
> >                          * treat all system events as shutdown request.
> >                          */
> >                         switch (cpu->kvm_run->system_event.type) {
> > -                       case KVM_SYSTEM_EVENT_RESET:
> > -                               /* Fall through for now */
> > -                       case KVM_SYSTEM_EVENT_SHUTDOWN:
> > -                               goto exit_kvm;
> >                         default:
> >                                 pr_warning("unknown system event type %d",
> >                                            cpu->kvm_run->system_event.type);
> > +                               /* fall through for now */
> > +                       case KVM_SYSTEM_EVENT_RESET:
> > +                               /* Fall through for now */
> > +                       case KVM_SYSTEM_EVENT_SHUTDOWN:
> > +                               /*
> > +                                * Ensure that VCPU #0 tears everything down if
> > +                                * the event was taken on a different VCPU.
> > +                                */
> > +                               if (cpu->cpu_id != 0)
> > +                                       pthread_kill(cpu->kvm->cpus[0]->thread,
> > +                                                    SIGKVMEXIT);
> 
> Could we use kvm_cpu__reboot() instead ?
> 
> That sends SIGKVMEXIT to all the VCPUs, and is used by the other
> paths which trigger a reboot/shutdown.

Sure; I'll spin a v2 with that and an updated comment.

Thanks,
Mark.