Re: [PATCH v2] replay: notify CPU on event

[Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru>]

On 29.03.2021 13:29, Paolo Bonzini wrote:
> On 29/03/21 09:43, Pavel Dovgalyuk wrote:
>> This patch enables vCPU notification to wake it up
>> when new async event comes in replay mode.
>>
>> The motivation of this patch is the following.
>> Consider recorded block async event. It is saved into the log
>> with one of the checkpoints. This checkpoint may be passed in
>> vCPU loop. In replay mode when this async event is read from
>> the log, and block thread task is not finished yet, vCPU thread
>> goes to sleep. That is why this patch adds waking up the vCPU
>> to process this finished event.
>>
>> Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
>> ---
>>   replay/replay-events.c |    1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/replay/replay-events.c b/replay/replay-events.c
>> index a1c6bb934e..92dc800219 100644
>> --- a/replay/replay-events.c
>> +++ b/replay/replay-events.c
>> @@ -126,6 +126,7 @@ void replay_add_event(ReplayAsyncEventKind 
>> event_kind,
>>       g_assert(replay_mutex_locked());
>>       QTAILQ_INSERT_TAIL(&events_list, event, events);
>> +    qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
>>   }
> 
> I still do not understand why the qemu_clock_notify function is used to 
> notify the CPU.  It would be nice to have a description of the call 
> chain in a comment or to have a more appropriate API.  I can queue the 
> patch since it's deep in replay-events.c and not in common code, but if 
> you post a short description here I'll integrate it.

Maybe I missed something.
This call is needed for the case when vCPU is waiting in rr_wait_io_event.
You mean that we can use qemu_cpu_kick instead?

Pavel Dovgalyuk