Re: [Qemu-devel] [RFC PATCH V6 09/18] cpu: add a tcg_executing flag.

[Frederic Konrad <fred.konrad@greensocs.com>]

On 07/07/2015 15:23, Alex Bennée wrote:
> fred.konrad@greensocs.com writes:
>
>> From: KONRAD Frederic <fred.konrad@greensocs.com>
>>
>> We need to know whether any other VCPU is executing code or not it's possible
>> with this flag.
> Reword: "This flag indicates if the vCPU is currently executing TCG code"?

Ok
>> Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
>> ---
>>   cpu-exec.c        | 1 +
>>   cpus.c            | 1 +
>>   include/qom/cpu.h | 3 +++
>>   qom/cpu.c         | 1 +
>>   4 files changed, 6 insertions(+)
>>
>> diff --git a/cpu-exec.c b/cpu-exec.c
>> index 0644383..de256d6 100644
>> --- a/cpu-exec.c
>> +++ b/cpu-exec.c
>> @@ -390,6 +390,7 @@ int cpu_exec(CPUArchState *env)
>>           cpu->halted = 0;
>>       }
>>   
>> +    cpu->tcg_executing = 1;
>>       current_cpu = cpu;
>>   
>>       rcu_read_lock();
>> diff --git a/cpus.c b/cpus.c
>> index 2541c56..0291620 100644
>> --- a/cpus.c
>> +++ b/cpus.c
>> @@ -1377,6 +1377,7 @@ static int tcg_cpu_exec(CPUArchState *env)
>>       }
>>       qemu_mutex_unlock_iothread();
>>       ret = cpu_exec(env);
>> +    cpu->tcg_executing = 0;
>
> This is an odd pairing, having the set in cpu_exec but the clear in the
> outer call to it. Any particular reason it is unbalanced?

true, no particular reason, I should move the clear in cpu_exec..
>
>>       qemu_mutex_lock_iothread();
>>   #ifdef CONFIG_PROFILER
>>       tcg_time += profile_getclock() - ti;
>> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
>> index af3c9e4..1464afa 100644
>> --- a/include/qom/cpu.h
>> +++ b/include/qom/cpu.h
>> @@ -222,6 +222,7 @@ struct kvm_run;
>>    * @stopped: Indicates the CPU has been artificially stopped.
>>    * @tcg_exit_req: Set to force TCG to stop executing linked TBs for this
>>    *           CPU and return to its top level loop.
>> + * @tcg_executing: This TCG thread is in cpu_exec().
>>    * @singlestep_enabled: Flags for single-stepping.
>>    * @icount_extra: Instructions until next timer event.
>>    * @icount_decr: Number of cycles left, with interrupt flag in high bit.
>> @@ -315,6 +316,8 @@ struct CPUState {
>>          (absolute value) offset as small as possible.  This reduces code
>>          size, especially for hosts without large memory offsets.  */
>>       volatile sig_atomic_t tcg_exit_req;
>> +
>> +    volatile int tcg_executing;
>>   };
>>   
>>   QTAILQ_HEAD(CPUTailQ, CPUState);
>> diff --git a/qom/cpu.c b/qom/cpu.c
>> index 108bfa2..ff41a4c 100644
>> --- a/qom/cpu.c
>> +++ b/qom/cpu.c
>> @@ -249,6 +249,7 @@ static void cpu_common_reset(CPUState *cpu)
>>       cpu->icount_decr.u32 = 0;
>>       cpu->can_do_io = 0;
>>       cpu->exception_index = -1;
>> +    cpu->tcg_executing = 0;
>>       memset(cpu->tb_jmp_cache, 0, TB_JMP_CACHE_SIZE * sizeof(void *));
>>   }