Re: fix qemu-kvm sigsegv at exit

[Gleb Natapov <gleb@redhat.com>]

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?

>          } else {
>              kvm_main_loop_wait(env, 1000);
>          }
> --
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--
			Gleb.