Re: [RFC PATCH v2 6/8] cpu: Declare cpu_has_work() in 'sysemu/tcg.h'

[Claudio Fontana]

On 3/4/21 11:23 PM, Philippe Mathieu-Daudé wrote:
> We can only check if a vCPU has work with TCG.
> Move the cpu_has_work() prototype to "sysemu/tcg.h".
> 
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
> RFC: could another accelerator do that?
>      can we rename this tcg_vcpu_has_work()?
> ---
>  include/hw/core/cpu.h | 16 ----------------
>  include/sysemu/tcg.h  | 11 +++++++++++
>  accel/tcg/cpu-exec.c  |  7 +++++++
>  softmmu/cpus.c        |  1 +
>  4 files changed, 19 insertions(+), 16 deletions(-)
> 
> diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
> index 1376e496a3f..66109bcca35 100644
> --- a/include/hw/core/cpu.h
> +++ b/include/hw/core/cpu.h
> @@ -670,22 +670,6 @@ CPUState *cpu_create(const char *typename);
>   */
>  const char *parse_cpu_option(const char *cpu_option);
>  
> -/**
> - * cpu_has_work:
> - * @cpu: The vCPU to check.
> - *
> - * Checks whether the CPU has work to do.
> - *
> - * Returns: %true if the CPU has work, %false otherwise.
> - */
> -static inline bool cpu_has_work(CPUState *cpu)
> -{
> -    CPUClass *cc = CPU_GET_CLASS(cpu);
> -
> -    g_assert(cc->has_work);
> -    return cc->has_work(cpu);
> -}
> -
>  /**
>   * qemu_cpu_is_self:
>   * @cpu: The vCPU to check against.
> diff --git a/include/sysemu/tcg.h b/include/sysemu/tcg.h
> index c16c13c3c69..3d46b0a7a93 100644
> --- a/include/sysemu/tcg.h
> +++ b/include/sysemu/tcg.h
> @@ -10,6 +10,7 @@
>  
>  #ifndef CONFIG_TCG
>  #define tcg_enabled() 0
> +#define cpu_has_work(cpu) false


I am not sure I like this approach,

it is misleading for the reader: cpu_has_work should not be called for TCG at 
all,
or at least a clue should be given that it is indeed a TCG-only function.

Otherwise, from the common code, the reader does not have any clue from the 
context that this is actually meaningful for TCG only.

Where is this actually used..?


>  #else
>  
>  void tcg_exec_init(unsigned long tb_size, int splitwx);
> @@ -26,6 +27,16 @@ extern bool tcg_allowed;
>  extern bool mttcg_enabled;
>  #define qemu_tcg_mttcg_enabled() (mttcg_enabled)
>  
> +/**
> + * cpu_has_work:
> + * @cpu: The vCPU to check.
> + *
> + * Checks whether the CPU has work to do.
> + *
> + * Returns: %true if the CPU has work, %false otherwise.
> + */
> +bool cpu_has_work(CPUState *cpu);
> +
>  #endif /* CONFIG_TCG */
>  
>  #endif
> diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
> index 7e67ade35b9..b9ce36e59e2 100644
> --- a/accel/tcg/cpu-exec.c
> +++ b/accel/tcg/cpu-exec.c
> @@ -447,6 +447,13 @@ static inline TranslationBlock *tb_find(CPUState *cpu,
>      return tb;
>  }
>  
> +bool cpu_has_work(CPUState *cpu)
> +{
> +    CPUClass *cc = CPU_GET_CLASS(cpu);
> +
> +    return cc->has_work(cpu);
> +}
> +
>  static inline bool cpu_handle_halt(CPUState *cpu)
>  {
>      if (cpu->halted) {
> diff --git a/softmmu/cpus.c b/softmmu/cpus.c
> index a7ee431187a..548ab9236f1 100644
> --- a/softmmu/cpus.c
> +++ b/softmmu/cpus.c
> @@ -42,6 +42,7 @@
>  #include "sysemu/runstate.h"
>  #include "sysemu/cpu-timers.h"
>  #include "sysemu/whpx.h"
> +#include "sysemu/tcg.h"
>  #include "hw/boards.h"
>  #include "hw/hw.h"
>  
>