Re: [Qemu-devel] [PATCH v2 09/12] cpus: introduce cpu_update_icount helper

[Alex Bennée]

Paolo Bonzini <address@hidden> writes:

> On 05/04/2017 15:25, Alex Bennée wrote:
>> +{
>> +    int64_t executed = cpu_get_icount_executed(cpu);
>> +    cpu->icount_budget -= executed;
>> +    atomic_add(&timers_state.qemu_icount, executed);
>> +}
>
> Since there's only one writer, it's also okay to do
>
>       atomic_set(&timers_state.qemu_icount,
>                  atomic_read(&timers_state.qemu_icount) + executed);
>
> (also not just faster, but also simpler to turn into TCG code if we do
> the update in gen_io_start).

OK fair enough. Annoyingly I've just noticed this breaks for 32 bit
hosts because we might not have CONFIG_ATOMIC64. What's the best
approach? #ifdef and handwave?

--
Alex Bennée