Re: [PULL 3/5] softmmu/cpus: Only set parallel_cpus for SMP

[Claudio Fontana]

On 9/7/20 12:20 PM, Philippe Mathieu-Daudé wrote:
> On 9/7/20 12:05 PM, Claudio Fontana wrote:
>> Hi Richard,
>>
>> currently rebasing on top of this one,
>> just a question, why is the patch not directly using "current_machine"?
> 
> For user mode?

In user mode I'd not expect softmmu/cpus.c to be built at all...

Ciao,

Claudio

> 
>>
>> Is using MACHINE(qdev_get_machine()) preferrable here?
>>
>> Thanks,
>>
>> Claudio
>>
>> On 9/3/20 11:40 PM, Richard Henderson wrote:
>>> Do not set parallel_cpus if there is only one cpu instantiated.
>>> This will allow tcg to use serial code to implement atomics.
>>>
>>> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>>> ---
>>>  softmmu/cpus.c | 11 ++++++++++-
>>>  1 file changed, 10 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/softmmu/cpus.c b/softmmu/cpus.c
>>> index a802e899ab..e3b98065c9 100644
>>> --- a/softmmu/cpus.c
>>> +++ b/softmmu/cpus.c
>>> @@ -1895,6 +1895,16 @@ static void qemu_tcg_init_vcpu(CPUState *cpu)
>>>      if (!tcg_region_inited) {
>>>          tcg_region_inited = 1;
>>>          tcg_region_init();
>>> +        /*
>>> +         * If MTTCG, and we will create multiple cpus,
>>> +         * then we will have cpus running in parallel.
>>> +         */
>>> +        if (qemu_tcg_mttcg_enabled()) {
>>> +            MachineState *ms = MACHINE(qdev_get_machine());
>>
>> MachineState *ms = current_machine;
>> ?
>>
>>
>>> +            if (ms->smp.max_cpus > 1) {
>>> +                parallel_cpus = true;
>>> +            }
>>> +        }
>>>      }
>>>  
>>>      if (qemu_tcg_mttcg_enabled() || !single_tcg_cpu_thread) {
>>> @@ -1904,7 +1914,6 @@ static void qemu_tcg_init_vcpu(CPUState *cpu)
>>>  
>>>          if (qemu_tcg_mttcg_enabled()) {
>>>              /* create a thread per vCPU with TCG (MTTCG) */
>>> -            parallel_cpus = true;
>>>              snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/TCG",
>>>                   cpu->cpu_index);
>>>  
>>>
>>
>>