From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: fix qemu-kvm sigsegv at exit
Date: Mon, 26 Oct 2009 17:05:14 -0200
Message-ID: <20091026190514.GA6736@amt.cnet>
References: <20091026184602.GB6016@amt.cnet> <20091026185849.GA5930@redhat.com>
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Cc: Avi Kivity <avi@redhat.com>, kvm <kvm@vger.kernel.org>
To: Gleb Natapov <gleb@redhat.com>
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On Mon, Oct 26, 2009 at 08:58:49PM +0200, Gleb Natapov wrote:
> On Mon, Oct 26, 2009 at 04:46:02PM -0200, Marcelo Tosatti wrote:
> > 
> > Michael reported a qemu-kvm SIGSEGV at shutdown:
> > 
> > Program received signal SIGSEGV, Segmentation fault.
> > [Switching to Thread 0x411d0940 (LWP 14446)]
> > 0x000000000040afb4 in qemu_mod_timer (ts=0x19f0fd0,
> > expire_time=62275467335)
> >     at /home/mst/scm/qemu-kvm/vl.c:1009
> > 1009            if ((alarm_timer->flags & ALARM_FLAG_EXPIRED) == 0)
> > {
> > (gdb) l
> > 1004        ts->next = *pt;
> > 1005        *pt = ts;
> > 1006
> > 1007        /* Rearm if necessary  */
> > 1008        if (pt == &active_timers[ts->clock->type]) {
> > 1009            if ((alarm_timer->flags & ALARM_FLAG_EXPIRED) == 0)
> > {
> > 1010          	qemu_rearm_alarm_timer(alarm_timer);
> > 1011            }
> > 1012            /* Interrupt execution to force deadline
> > recalculation.  */
> > 1013            if (use_icount)
> > (gdb) p alarm_timer
> > $1 = (struct qemu_alarm_timer *) 0x0
> > 
> > Problem is kvm_main_loop_wait(env, 0) can process the stop request
> > (signalling iothread that vcpu is stopped, so its OK to exit) and
> > continue to kvm_cpu_exec.
> > 
> > Make sure cpu is not stopped before proceeding to kvm_cpu_exec.
> > 
> > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> > Reported-by: "Michael S. Tsirkin" <mst@redhat.com>
> > 
> > diff --git a/qemu-kvm.c b/qemu-kvm.c
> > index 4c13628..ab8f0e4 100644
> > --- a/qemu-kvm.c
> > +++ b/qemu-kvm.c
> > @@ -1868,7 +1868,8 @@ static int kvm_main_loop_cpu(CPUState *env)
> >          }
> >          if (run_cpu) {
> >              kvm_main_loop_wait(env, 0);
> > -            kvm_cpu_exec(env);
> > +            if (!is_cpu_stopped(env))
> > +                kvm_cpu_exec(env);
> I wonder if calling kvm_cpu_exec() after kvm_main_loop_wait() will fix
> the problem?

Yeah, that would also do it.