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

Marcelo Tosatti
2010-06-21T20:45:22Z

On Mon, Jun 21, 2010 at 12:01:52PM +0300, 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);

Can't you check for env->stopped instead?

>
> 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();
> }
> --
> Gleb.