How does Xen's Guest Domain wake up..?

叫醒Guest Domain，别总睡啦，Xen喊你干活啦!!

void vcpu_unblock(struct vcpu *v)
{
if ( !test_and_clear_bit(_VPF_blocked, &v->pause_flags) )
return;

/* Polling period ends when a VCPU is unblocked. */
if ( unlikely(v->poll_evtchn != 0) ){
v->poll_evtchn = 0;
/*
* We *must* re-clear _VPF_blocked to avoid racing other wakeups of
* this VCPU (and it then going back to sleep on poll_mask).
* Test-and-clear is idiomatic and ensures clear_bit not reordered.
*/
if ( test_and_clear_bit(v->vcpu_id, v->domain->poll_mask) )
clear_bit(_VPF_blocked, &v->pause_flags);
}

vcpu_wake(v);
}

void vcpu_wake(struct vcpu *v)
{
unsigned long flags;

vcpu_schedule_lock_irqsave(v, flags);

if ( likely(vcpu_runnable(v)) ) {
if ( v->runstate.state == RUNSTATE_blocked||v->runstate.state == RUNSTATE_offline)

vcpu_runstate_change(v, RUNSTATE_runnable, NOW());

SCHED_OP(wake, v);
} else if ( !test_bit(_VPF_blocked, &v->pause_flags) ) {
if ( v->runstate.state == RUNSTATE_blocked )
vcpu_runstate_change(v, RUNSTATE_offline, NOW());
}

vcpu_schedule_unlock_irqrestore(v, flags);

}

static voidcsched_vcpu_wake(struct vcpu *vc)
{
struct csched_vcpu * const svc = CSCHED_VCPU(vc);
const unsigned int cpu = vc->processor;

if ( svc->pri == CSCHED_PRI_TS_UNDER &&
!(svc->flags & CSCHED_FLAG_VCPU_PARKED) ){
svc->pri = CSCHED_PRI_TS_BOOST;
}

/* Put the VCPU on the runq and tickle CPUs */
__runq_insert(cpu, svc);
__runq_tickle(cpu, svc); //重新调度，支持抢占
}

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/* VCPU is currently running on a physical CPU. */
#define RUNSTATE_running 0

/* VCPU is runnable, but not currently scheduled on any physical CPU. */
#define RUNSTATE_runnable 1

/* VCPU is blocked (a.k.a. idle). It is therefore not runnable. */
#define RUNSTATE_blocked 2

/*
* VCPU is not runnable, but it is not blocked.
* This is a 'catch all' state for things like hotplug and pauses by the
* system administrator (or for critical sections in the hypervisor).
* RUNSTATE_blocked dominates this state (it is the preferred state).
*/
#define RUNSTATE_offline 3

------------------------------------------------------------------------------------------------

struct vcpu *alloc_vcpu(struct domain *d, unsigned int vcpu_id, unsigned int cpu_id)
{
struct vcpu *v;

if ( (v = alloc_vcpu_struct()) == NULL )
return NULL;

v->domain = d;
v->vcpu_id = vcpu_id;

if ( is_idle_domain(d) ) {
v->runstate.state = RUNSTATE_running;
} else {
v->runstate.state = RUNSTATE_offline;
v->runstate.state_entry_time = NOW();
set_bit(_VPF_down, &v->pause_flags);
v->vcpu_info = (void *)&shared_info(d, vcpu_info[vcpu_id]);
}

if ( sched_init_vcpu(v, cpu_id) != 0 ) {
free_vcpu_struct(v);
return NULL;
}

}