Re: [PATCH] do not enter vcpu again if it was stopped during IO

[Jan Kiszka <jan.kiszka@siemens.com>]

Gleb Natapov wrote:
> To prevent reentering vcpu after IO completion it is not enough
> to set env->stopped since it is checked only in main loop but control
> will not get there until next non-IO exit since kvm_run() will reenter
> vcpu to complete IO instruction. Solve this by sending self-signal to
> request exit after IO instruction completion.
> 
> Signed-off-by: Gleb Natapov <gleb@redhat.com>
> diff --git a/qemu-kvm.c b/qemu-kvm.c
> index be1dac2..4f7cf6d 100644
> --- a/qemu-kvm.c
> +++ b/qemu-kvm.c
> @@ -603,6 +603,10 @@ int kvm_run(CPUState *env)
>      r = pre_kvm_run(kvm, env);
>      if (r)
>          return r;
> +    if (env->exit_request) {
> +        env->exit_request = 0;
> +        pthread_kill(env->kvm_cpu_state.thread, SIG_IPI);
> +    }
>      r = ioctl(fd, KVM_RUN, 0);
>  
>      if (r == -1 && errno != EINTR && errno != EAGAIN) {
> diff --git a/vl.c b/vl.c
> index 9e9c176..dcfab13 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -1817,6 +1817,7 @@ void qemu_system_reset_request(void)
>      }
>      if (cpu_single_env) {
>          cpu_single_env->stopped = 1;
> +        cpu_exit(cpu_single_env);
>      }
>      qemu_notify_event();
>  }

What does this second hunk do, specifically in the context of I/O
processing? The changelog does not mention it explicitly (or I'm missing
the obvious).

Jan

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