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

[Philippe Mathieu-Daudé]

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?

> 
> 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);
>>  
>>
> 
>