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

["Alex Bennée" <alex.bennee@linaro.org>]

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"?
>
> 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?

>      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 *));
>  }

-- 
Alex Bennée