Re: [patch uq/master 2/4] qemu: kvm specific wait_io_event

[Avi Kivity <avi@redhat.com>]

On 02/18/2010 12:14 AM, Marcelo Tosatti wrote:
> In KVM mode the global mutex is released when vcpus are executing,
> which means acquiring the fairness mutex is not required.
>
> Also for KVM there is one thread per vcpu, so tcg_has_work is meaningless.
>
> Add a new qemu_wait_io_event_common function to hold common code
> between TCG/KVM.
>
> Signed-off-by: Marcelo Tosatti<mtosatti@redhat.com>
>
> Index: qemu/vl.c
> ===================================================================
> --- qemu.orig/vl.c
> +++ qemu/vl.c
> @@ -3382,6 +3382,7 @@ static QemuCond qemu_pause_cond;
>   static void block_io_signals(void);
>   static void unblock_io_signals(void);
>   static int tcg_has_work(void);
> +static int cpu_has_work(CPUState *env);
>
>   static int qemu_init_main_loop(void)
>   {
> @@ -3402,6 +3403,15 @@ static int qemu_init_main_loop(void)
>       return 0;
>   }
>
> +static void qemu_wait_io_event_common(CPUState *env)
> +{
> +    if (env->stop) {
> +        env->stop = 0;
> +        env->stopped = 1;
> +        qemu_cond_signal(&qemu_pause_cond);
> +    }
> +}
> +
>   static void qemu_wait_io_event(CPUState *env)
>   {
>       while (!tcg_has_work())
> @@ -3418,11 +3428,15 @@ static void qemu_wait_io_event(CPUState
>       qemu_mutex_unlock(&qemu_fair_mutex);
>
>       qemu_mutex_lock(&qemu_global_mutex);
> -    if (env->stop) {
> -        env->stop = 0;
> -        env->stopped = 1;
> -        qemu_cond_signal(&qemu_pause_cond);
> -    }
> +    qemu_wait_io_event_common(env);
> +}
> +
> +static void qemu_kvm_wait_io_event(CPUState *env)
> +{
> +    while (!cpu_has_work(env))
> +        qemu_cond_timedwait(env->halt_cond,&qemu_global_mutex, 1000);
> +
> +    qemu_wait_io_event_common(env);
>   }
>    

Shouldn't kvm specific code be in kvm-all.c?

>
>   static int qemu_cpu_exec(CPUState *env);
> @@ -3448,7 +3462,7 @@ static void *kvm_cpu_thread_fn(void *arg
>       while (1) {
>           if (cpu_can_run(env))
>               qemu_cpu_exec(env);
> -        qemu_wait_io_event(env);
> +        qemu_kvm_wait_io_event(env);
>       }
>
>       return NULL;
>    

Well, kvm_cpu_thread_fn() apparently isn't.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.