* fix qemu-kvm sigsegv at exit
@ 2009-10-26 18:46 Marcelo Tosatti
2009-10-26 18:58 ` Gleb Natapov
0 siblings, 1 reply; 7+ messages in thread
From: Marcelo Tosatti @ 2009-10-26 18:46 UTC (permalink / raw)
To: Avi Kivity; +Cc: kvm
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);
} else {
kvm_main_loop_wait(env, 1000);
}
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: fix qemu-kvm sigsegv at exit
2009-10-26 18:46 fix qemu-kvm sigsegv at exit Marcelo Tosatti
@ 2009-10-26 18:58 ` Gleb Natapov
2009-10-26 19:05 ` Marcelo Tosatti
2009-10-27 15:33 ` [PATCH v2] " Marcelo Tosatti
0 siblings, 2 replies; 7+ messages in thread
From: Gleb Natapov @ 2009-10-26 18:58 UTC (permalink / raw)
To: Marcelo Tosatti; +Cc: Avi Kivity, kvm
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);
> }
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Gleb.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: fix qemu-kvm sigsegv at exit
2009-10-26 18:58 ` Gleb Natapov
@ 2009-10-26 19:05 ` Marcelo Tosatti
2009-10-27 15:33 ` [PATCH v2] " Marcelo Tosatti
1 sibling, 0 replies; 7+ messages in thread
From: Marcelo Tosatti @ 2009-10-26 19:05 UTC (permalink / raw)
To: Gleb Natapov; +Cc: Avi Kivity, kvm
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.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v2] fix qemu-kvm sigsegv at exit
2009-10-26 18:58 ` Gleb Natapov
2009-10-26 19:05 ` Marcelo Tosatti
@ 2009-10-27 15:33 ` Marcelo Tosatti
2009-10-28 9:42 ` Avi Kivity
1 sibling, 1 reply; 7+ messages in thread
From: Marcelo Tosatti @ 2009-10-27 15:33 UTC (permalink / raw)
To: Gleb Natapov; +Cc: Avi Kivity, kvm
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.
Reorder kvm_main_loop_wait and kvm_cpu_exec, as suggested by Gleb.
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..809fd65 100644
--- a/qemu-kvm.c
+++ b/qemu-kvm.c
@@ -1867,8 +1867,8 @@ static int kvm_main_loop_cpu(CPUState *env)
run_cpu = !env->halted;
}
if (run_cpu) {
- kvm_main_loop_wait(env, 0);
kvm_cpu_exec(env);
+ kvm_main_loop_wait(env, 0);
} else {
kvm_main_loop_wait(env, 1000);
}
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v2] fix qemu-kvm sigsegv at exit
2009-10-27 15:33 ` [PATCH v2] " Marcelo Tosatti
@ 2009-10-28 9:42 ` Avi Kivity
2009-10-28 22:38 ` Marcelo Tosatti
0 siblings, 1 reply; 7+ messages in thread
From: Avi Kivity @ 2009-10-28 9:42 UTC (permalink / raw)
To: Marcelo Tosatti; +Cc: Gleb Natapov, kvm
On 10/27/2009 05:33 PM, 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.
>
> Reorder kvm_main_loop_wait and kvm_cpu_exec, as suggested by Gleb.
>
> 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..809fd65 100644
> --- a/qemu-kvm.c
> +++ b/qemu-kvm.c
> @@ -1867,8 +1867,8 @@ static int kvm_main_loop_cpu(CPUState *env)
> run_cpu = !env->halted;
> }
> if (run_cpu) {
> - kvm_main_loop_wait(env, 0);
> kvm_cpu_exec(env);
> + kvm_main_loop_wait(env, 0);
> } else {
> kvm_main_loop_wait(env, 1000);
> }
>
This will miss an event at the very beginning of the loop (powerdown
requested before we had a chance to spin up?). I think it should be
fine since there will be a pending signal which will break us out of
kvm_cpu_exec() before it has a chance to do anything (i.e. spin in the
guest).
So, I think it's fine, but please double check the above.
--
error compiling committee.c: too many arguments to function
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] fix qemu-kvm sigsegv at exit
2009-10-28 9:42 ` Avi Kivity
@ 2009-10-28 22:38 ` Marcelo Tosatti
2009-11-01 15:39 ` Avi Kivity
0 siblings, 1 reply; 7+ messages in thread
From: Marcelo Tosatti @ 2009-10-28 22:38 UTC (permalink / raw)
To: Avi Kivity; +Cc: Gleb Natapov, kvm
On Wed, Oct 28, 2009 at 11:42:56AM +0200, Avi Kivity wrote:
> On 10/27/2009 05:33 PM, 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.
>>
>> Reorder kvm_main_loop_wait and kvm_cpu_exec, as suggested by Gleb.
>>
>> 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..809fd65 100644
>> --- a/qemu-kvm.c
>> +++ b/qemu-kvm.c
>> @@ -1867,8 +1867,8 @@ static int kvm_main_loop_cpu(CPUState *env)
>> run_cpu = !env->halted;
>> }
>> if (run_cpu) {
>> - kvm_main_loop_wait(env, 0);
>> kvm_cpu_exec(env);
>> + kvm_main_loop_wait(env, 0);
>> } else {
>> kvm_main_loop_wait(env, 1000);
>> }
>>
>
> This will miss an event at the very beginning of the loop (powerdown
> requested before we had a chance to spin up?). I think it should be
> fine since there will be a pending signal which will break us out of
> kvm_cpu_exec() before it has a chance to do anything (i.e. spin in the
> guest).
>
> So, I think it's fine, but please double check the above.
That can happen but only with the unpatched version, where
kvm_main_loop_wait eats the signal, sets env->stopped = 1,
and proceeds to kvm_cpu_exec.
With the patch, this is not the case.
As before, the signal sender will send an IPI with smp_send_reschedule
(and vcpu_enter_guest checks sigpending after disabling interrupts).
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] fix qemu-kvm sigsegv at exit
2009-10-28 22:38 ` Marcelo Tosatti
@ 2009-11-01 15:39 ` Avi Kivity
0 siblings, 0 replies; 7+ messages in thread
From: Avi Kivity @ 2009-11-01 15:39 UTC (permalink / raw)
To: Marcelo Tosatti; +Cc: Gleb Natapov, kvm
On 10/29/2009 12:38 AM, Marcelo Tosatti wrote:
>
>> This will miss an event at the very beginning of the loop (powerdown
>> requested before we had a chance to spin up?). I think it should be
>> fine since there will be a pending signal which will break us out of
>> kvm_cpu_exec() before it has a chance to do anything (i.e. spin in the
>> guest).
>>
>> So, I think it's fine, but please double check the above.
>>
> That can happen but only with the unpatched version, where
> kvm_main_loop_wait eats the signal, sets env->stopped = 1,
> and proceeds to kvm_cpu_exec.
> With the patch, this is not the case.
>
> As before, the signal sender will send an IPI with smp_send_reschedule
> (and vcpu_enter_guest checks sigpending after disabling interrupts).
>
Fair enough, double bugfix; applied, thanks.
--
error compiling committee.c: too many arguments to function
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2009-11-01 15:39 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
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2009-10-26 18:46 fix qemu-kvm sigsegv at exit Marcelo Tosatti
2009-10-26 18:58 ` Gleb Natapov
2009-10-26 19:05 ` Marcelo Tosatti
2009-10-27 15:33 ` [PATCH v2] " Marcelo Tosatti
2009-10-28 9:42 ` Avi Kivity
2009-10-28 22:38 ` Marcelo Tosatti
2009-11-01 15:39 ` Avi Kivity
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