Re: [PATCH v3 57/68] accel/tcg: Expose vcpu_[un]register() for MTTCG

[Richard Henderson <richard.henderson@linaro.org>]

On 7/1/25 08:40, Philippe Mathieu-Daudé wrote:
> Allocate ForceRcuNotifier on the Heap.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>   accel/tcg/tcg-accel-ops-mttcg.c | 30 ++++++++++++++++++++++++------
>   1 file changed, 24 insertions(+), 6 deletions(-)

Please document the motivation.

r~

> 
> diff --git a/accel/tcg/tcg-accel-ops-mttcg.c b/accel/tcg/tcg-accel-ops-mttcg.c
> index 4de506a80ca..2d31b00ee59 100644
> --- a/accel/tcg/tcg-accel-ops-mttcg.c
> +++ b/accel/tcg/tcg-accel-ops-mttcg.c
> @@ -55,6 +55,27 @@ static void mttcg_force_rcu(Notifier *notify, void *data)
>       async_run_on_cpu(cpu, do_nothing, RUN_ON_CPU_NULL);
>   }
>   
> +static void *mttcg_vcpu_register(CPUState *cpu)
> +{
> +    MttcgForceRcuNotifier *force_rcu = g_new(MttcgForceRcuNotifier, 1);
> +
> +    force_rcu->notifier.notify = mttcg_force_rcu;
> +    force_rcu->cpu = cpu;
> +    rcu_add_force_rcu_notifier(&force_rcu->notifier);
> +    tcg_register_thread();
> +
> +    return force_rcu;
> +}
> +
> +static void mttcg_vcpu_unregister(CPUState *cpu, void *opaque)
> +{
> +    MttcgForceRcuNotifier *force_rcu = opaque;
> +
> +    rcu_remove_force_rcu_notifier(&force_rcu->notifier);
> +
> +    g_free(force_rcu);
> +}
> +
>   /*
>    * In the multi-threaded case each vCPU has its own thread. The TLS
>    * variable current_cpu can be used deep in the code to find the
> @@ -63,17 +84,14 @@ static void mttcg_force_rcu(Notifier *notify, void *data)
>   
>   void *mttcg_cpu_thread_routine(void *arg)
>   {
> -    MttcgForceRcuNotifier force_rcu;
> +    MttcgForceRcuNotifier *force_rcu;
>       CPUState *cpu = arg;
>   
>       assert(tcg_enabled());
>       g_assert(!icount_enabled());
>   
>       rcu_register_thread();
> -    force_rcu.notifier.notify = mttcg_force_rcu;
> -    force_rcu.cpu = cpu;
> -    rcu_add_force_rcu_notifier(&force_rcu.notifier);
> -    tcg_register_thread();
> +    force_rcu = mttcg_vcpu_register(cpu);
>   
>       bql_lock();
>       qemu_thread_get_self(cpu->thread);
> @@ -121,7 +139,7 @@ void *mttcg_cpu_thread_routine(void *arg)
>   
>       tcg_cpu_destroy(cpu);
>       bql_unlock();
> -    rcu_remove_force_rcu_notifier(&force_rcu.notifier);
> +    mttcg_vcpu_unregister(cpu, force_rcu);
>       rcu_unregister_thread();
>       return NULL;
>   }