Re: [Qemu-devel] [PATCH v7 03/14] replay: exception replay fix

[Paolo Bonzini]

On 25/01/2017 13:27, Pavel Dovgalyuk wrote:
>> From: Paolo Bonzini [mailto:address@hidden
>> On 25/01/2017 12:33, Pavel Dovgalyuk wrote:
>>>> From: Paolo Bonzini [mailto:address@hidden
>>>> On 25/01/2017 12:12, Pavel Dovgalyuk wrote:
>>>>>> From: Paolo Bonzini [mailto:address@hidden
>>>>>> On 24/01/2017 08:17, Pavel Dovgalyuk wrote:
>>>>>>> @@ -451,6 +451,10 @@ static inline bool cpu_handle_exception(CPUState 
>>>>>>> *cpu, int *ret)
>>>>>>>  #ifndef CONFIG_USER_ONLY
>>>>>>>      } else if (replay_has_exception()
>>>>>>>                 && cpu->icount_decr.u16.low + cpu->icount_extra == 0) {
>>>>>>> +        /* Break the execution loop in case of running out of TB cache.
>>>>>>> +           This is needed to make flushing of the TB cache, because
>>>>>>> +           real flush is queued to be executed outside the cpu loop. */
>>>>>>> +        cpu->exception_index = EXCP_INTERRUPT;
>>>>>>>          /* try to cause an exception pending in the log */
>>>>>>>          cpu_exec_nocache(cpu, 1, tb_find(cpu, NULL, 0), true);
>>>>>>>          *ret = -1;
>>>>>>
>>>>>> Why is replay_has_exception() related to be running out of TB cache?
>>>>>
>>>>> It doesn't.
>>>>> Calling tb_find when there is not space in cache causes tb_flush and 
>>>>> cpu_loop_exit.
>>>>> But execution loop will continue, because there is no reason to break it
>>>>> (like setting exception_index).
>>>>
>>>> What about setting cpu->exit_request?  queue_work_on_cpu calls
>>>> qemu_cpu_kick.
>>>
>>> cpu->exit_request does not checked in this loop.
>>> We have to add this checking somewhere then?
>>
>> It's checked by cpu_handle_interrupt.  Are you not reaching
>> cpu_handle_interrupt then?  Why?
> 
> Execution doesn't reach cpu_handle_interrupt, because tb_find 
> calls cpu_loop_exit. And the execution loop enters cpu_handle_exception again 
> and again.

Perhaps tb_gen_code should set cpu->exception_index before calling
cpu_loop_exit.

Paolo

> Pavel Dovgalyuk
>