Re: [Qemu-devel] [RFC v3 09/13] cpus.c: introduce simple callback support

[Paolo Bonzini <pbonzini@redhat.com>]

On 10/07/2015 10:23, Alvise Rigo wrote:
> In order to perfom "lazy" TLB invalidation requests, introduce a
> queue of callbacks at every vCPU disposal that will be fired just
> before entering the next TB.
> 
> Suggested-by: Jani Kokkonen <jani.kokkonen@huawei.com>
> Suggested-by: Claudio Fontana <claudio.fontana@huawei.com>
> Signed-off-by: Alvise Rigo <a.rigo@virtualopensystems.com>

Why is async_run_on_cpu not enough?

Paolo

> ---
>  cpus.c            | 34 ++++++++++++++++++++++++++++++++++
>  exec.c            |  1 +
>  include/qom/cpu.h | 20 ++++++++++++++++++++
>  3 files changed, 55 insertions(+)
> 
> diff --git a/cpus.c b/cpus.c
> index f4d938e..b9f0329 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -1421,6 +1421,7 @@ static int tcg_cpu_exec(CPUArchState *env)
>          cpu->icount_extra = count;
>      }
>      qemu_mutex_unlock_iothread();
> +    cpu_exit_callbacks_call_all(cpu);
>      ret = cpu_exec(env);
>      cpu->tcg_executing = 0;
>  
> @@ -1469,6 +1470,39 @@ static void tcg_exec_all(CPUState *cpu)
>      cpu->exit_request = 0;
>  }
>  
> +void cpu_exit_callback_add(CPUState *cpu, CPUExitCallback callback,
> +                           void *opaque)
> +{
> +    CPUExitCB *cb;
> +
> +    cb = g_malloc(sizeof(*cb));
> +    cb->callback = callback;
> +    cb->opaque = opaque;
> +
> +    qemu_mutex_lock(&cpu->exit_cbs.mutex);
> +    QTAILQ_INSERT_TAIL(&cpu->exit_cbs.exit_callbacks, cb, entry);
> +    qemu_mutex_unlock(&cpu->exit_cbs.mutex);
> +}
> +
> +void cpu_exit_callbacks_call_all(CPUState *cpu)
> +{
> +    CPUExitCB *cb, *next;
> +
> +    if (QTAILQ_EMPTY(&cpu->exit_cbs.exit_callbacks)) {
> +        return;
> +    }
> +
> +    QTAILQ_FOREACH_SAFE(cb, &cpu->exit_cbs.exit_callbacks, entry, next) {
> +        cb->callback(cpu, cb->opaque);
> +
> +        /* one-shot callbacks, remove it after using it */
> +        qemu_mutex_lock(&cpu->exit_cbs.mutex);
> +        QTAILQ_REMOVE(&cpu->exit_cbs.exit_callbacks, cb, entry);
> +        g_free(cb);
> +        qemu_mutex_unlock(&cpu->exit_cbs.mutex);
> +    }
> +}
> +
>  void list_cpus(FILE *f, fprintf_function cpu_fprintf, const char *optarg)
>  {
>      /* XXX: implement xxx_cpu_list for targets that still miss it */
> diff --git a/exec.c b/exec.c
> index 51958ed..322f2c6 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -531,6 +531,7 @@ void cpu_exec_init(CPUArchState *env)
>      cpu->numa_node = 0;
>      QTAILQ_INIT(&cpu->breakpoints);
>      QTAILQ_INIT(&cpu->watchpoints);
> +    QTAILQ_INIT(&cpu->exit_cbs.exit_callbacks);
>  #ifndef CONFIG_USER_ONLY
>      cpu->as = &address_space_memory;
>      cpu->thread_id = qemu_get_thread_id();
> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> index 8d121b3..0ec020b 100644
> --- a/include/qom/cpu.h
> +++ b/include/qom/cpu.h
> @@ -201,6 +201,24 @@ typedef struct CPUWatchpoint {
>      QTAILQ_ENTRY(CPUWatchpoint) entry;
>  } CPUWatchpoint;
>  
> +/* vCPU exit callbacks */
> +typedef void (*CPUExitCallback)(CPUState *cpu, void *opaque);
> +struct CPUExitCBs {
> +    QemuMutex mutex;
> +    QTAILQ_HEAD(exit_callbacks_head, CPUExitCB) exit_callbacks;
> +};
> +
> +typedef struct CPUExitCB {
> +    CPUExitCallback callback;
> +    void *opaque;
> +
> +    QTAILQ_ENTRY(CPUExitCB) entry;
> +} CPUExitCB;
> +
> +void cpu_exit_callback_add(CPUState *cpu, CPUExitCallback callback,
> +                           void *opaque);
> +void cpu_exit_callbacks_call_all(CPUState *cpu);
> +
>  /* Rendezvous support */
>  #define TCG_RDV_POLLING_PERIOD 10
>  typedef struct CpuExitRendezvous {
> @@ -305,6 +323,8 @@ struct CPUState {
>  
>      void *opaque;
>  
> +    /* One-shot callbacks for stopping requests. */
> +    struct CPUExitCBs exit_cbs;
>      volatile int pending_rdv;
>  
>      /* In order to avoid passing too many arguments to the MMIO helpers,
>