Xen Event Channel (2)
Xen Event Channel (2) static long evtchn_bind_ipi(evtchn_bind_ipi_t *bind){
struct evtchn *chn;
struct domain *d = current->domain; // 当前dom
int port, vcpu = bind->vcpu;
long rc = 0;
if ( (vcpu < 0) || (vcpu >= d->max_vcpus) ||
(d->vcpu == NULL) )
return -ENOENT;
spin_lock(&d->event_lock);
if ( (port = get_free_port(d)) < 0 ) // 获得一个port
ERROR_EXIT(port);
chn = evtchn_from_port(d, port); // 获得port对应的evtchn
chn->state = ECS_IPI;
chn->notify_vcpu_id = vcpu; // evtchn的IPI绑定，即设置此evtchn的notify_vcpu_id
bind->port = port; // 设置输出参数
out:
spin_unlock(&d->event_lock);
return rc;
}
static long evtchn_bind_pirq(evtchn_bind_pirq_t *bind)
{
struct evtchn *chn;
struct domain *d = current->domain;
int port, pirq = bind->pirq;
long rc;
if ( (pirq < 0) || (pirq >= d->nr_pirqs) )
return -EINVAL;
if ( !irq_access_permitted(d, pirq) )
return -EPERM;
spin_lock(&d->event_lock);
if ( d->pirq_to_evtchn != 0 )
ERROR_EXIT(-EEXIST);
if ( (port = get_free_port(d)) < 0 ) // 分配一个free的port
ERROR_EXIT(port);
chn = evtchn_from_port(d, port); // 获得对应的evtchn
d->pirq_to_evtchn = port; // PIRQ绑定的port设置到dom的pirq_to_evtchn
rc = pirq_guest_bind(d->vcpu, pirq,
!!(bind->flags & BIND_PIRQ__WILL_SHARE));
if ( rc != 0 )
{
d->pirq_to_evtchn = 0;
goto out;
}
chn->state= ECS_PIRQ;
chn->u.pirq = pirq; // PIRQ绑定
bind->port = port; // 设置输出参数
out:
spin_unlock(&d->event_lock);
return rc;
}
static long __evtchn_close(struct domain *d1, int port1)
{
struct domain *d2 = NULL;
struct vcpu *v;
struct evtchn *chn1, *chn2;
int port2;
long rc = 0;
again:
spin_lock(&d1->event_lock);
if ( !port_is_valid(d1, port1) )
{
rc = -EINVAL;
goto out;
}
chn1 = evtchn_from_port(d1, port1); // 得到对应的evtchn
/* Guest cannot close a Xen-attached event channel. */
if ( unlikely(chn1->consumer_is_xen) )
{
rc = -EINVAL;
goto out;
}
switch ( chn1->state )
{
case ECS_FREE:
case ECS_RESERVED:
rc = -EINVAL;
goto out;
case ECS_UNBOUND:
break;
case ECS_PIRQ:
pirq_guest_unbind(d1, chn1->u.pirq);
d1->pirq_to_evtchn = 0;
break;
case ECS_VIRQ:
for_each_vcpu ( d1, v )
{
if ( v->virq_to_evtchn != port1 )
continue;
v->virq_to_evtchn = 0;
spin_barrier_irq(&v->virq_lock);
}
break;
case ECS_IPI:
break;
case ECS_INTERDOMAIN:
if ( d2 == NULL )
{
d2 = chn1->u.interdomain.remote_dom;
/* If we unlock d1 then we could lose d2. Must get a reference. */
if ( unlikely(!get_domain(d2)) )
BUG();
if ( d1 < d2 )
{
spin_lock(&d2->event_lock);
}
else if ( d1 != d2 )
{
spin_unlock(&d1->event_lock);
spin_lock(&d2->event_lock);
goto again;
}
}
else if ( d2 != chn1->u.interdomain.remote_dom )
{
/*
* We can only get here if the port was closed and re-bound after
* unlocking d1 but before locking d2 above. We could retry but
* it is easier to return the same error as if we had seen the
* port in ECS_CLOSED. It must have passed through that state for
* us to end up here, so it's a valid error to return.
*/
rc = -EINVAL;
goto out;
}
port2 = chn1->u.interdomain.remote_port; // 获得远端port
BUG_ON(!port_is_valid(d2, port2));
chn2 = evtchn_from_port(d2, port2); // 获得对应的evtchn
BUG_ON(chn2->state != ECS_INTERDOMAIN);
BUG_ON(chn2->u.interdomain.remote_dom != d1);
chn2->state = ECS_UNBOUND; //设置远端为alloc之后，绑定之前的状态
chn2->u.unbound.remote_domid = d1->domain_id; // ECS_UNBOUND
break;
default:
BUG();
}
/* Clear pending event to avoid unexpected behavior on re-bind. */
clear_bit(port1, &shared_info(d1, evtchn_pending));
/* Reset binding to vcpu0 when the channel is freed. */
chn1->state = ECS_FREE; // 设置本地为ECS_FREE状态
chn1->notify_vcpu_id = 0; // 设置初始化状态绑定的VCPU为0
xsm_evtchn_close_post(chn1);
out:
if ( d2 != NULL )
{
if ( d1 != d2 )
spin_unlock(&d2->event_lock);
put_domain(d2);
}
spin_unlock(&d1->event_lock);
return rc;
}
static long evtchn_close(evtchn_close_t *close)
{
return __evtchn_close(current->domain, close->port);
}
int evtchn_send(struct domain *d, unsigned int lport)
d为本地dom。是current->domain
lport为本地port，要send的对象
{
struct evtchn *lchn, *rchn;
struct domain *ld = d, *rd;
struct vcpu *rvcpu;
int rport, ret = 0;
spin_lock(&ld->event_lock);
if ( unlikely(!port_is_valid(ld, lport)) )
{
spin_unlock(&ld->event_lock);
return -EINVAL;
}
lchn = evtchn_from_port(ld, lport); // 首先获得lport对应的本地evtchn
/* Guest cannot send via a Xen-attached event channel. */
if ( unlikely(lchn->consumer_is_xen) )
{
spin_unlock(&ld->event_lock);
return -EINVAL;
}
ret = xsm_evtchn_send(ld, lchn);
if ( ret )
goto out;
switch ( lchn->state )
{
case ECS_INTERDOMAIN: // 域间通信
rd = lchn->u.interdomain.remote_dom; // 获得远端/对点的rdom
rport = lchn->u.interdomain.remote_port; // 获得远端/对点的rport
rchn= evtchn_from_port(rd, rport); // 获得rport对应的rchn
rvcpu = rd->vcpu; // 获得对点evtchn绑定的VCPU
if ( rchn->consumer_is_xen )
{
/* Xen consumers need notification only if they are blocked. */
if ( test_and_clear_bit(_VPF_blocked_in_xen,
&rvcpu->pause_flags) )
vcpu_wake(rvcpu);
}
else
{
evtchn_set_pending(rvcpu, rport); // 设置对点VCPU上的port有event发生。
} // 下面将异步进行event句柄的处理。
break;
case ECS_IPI:
evtchn_set_pending(ld->vcpu, lport); // IPI的话，则设置对应的VCPU
break;
case ECS_UNBOUND:
/* silently drop the notification */
break;
default: // ESC_VIRQ & ESC_PIRQ不会到这里来
ret = -EINVAL; // 因为这些notification是的发送方是Xen，不需要用hypercall
}
out:
spin_unlock(&ld->event_lock);
return ret;
}
long evtchn_bind_vcpu(unsigned int port, unsigned int vcpu_id)
{
绑定VCPU之后，这个event的处理就由该VCPU来完成。
evtchn的屏蔽：
1） 所有的VCPU屏蔽某个evtchn
设置evtchn的MASK位。这个MASK位在struct shared_info里面。
2） 某个VCPU屏蔽所有evtchn
此VCPU结构体struct vcpu_info成员完成。方法在结构体处说明。
struct domain *d = current->domain;
struct evtchn *chn;
long rc = 0;
if ( (vcpu_id >= d->max_vcpus) || (d->vcpu == NULL) )
return -ENOENT;
spin_lock(&d->event_lock);
if ( !port_is_valid(d, port) )
{
rc = -EINVAL;
goto out;
}
chn = evtchn_from_port(d, port); // 根据port得到evtchn
/* Guest cannot re-bind a Xen-attached event channel. */
if ( unlikely(chn->consumer_is_xen) )
{
rc = -EINVAL;
goto out;
}
switch ( chn->state )
{
case ECS_VIRQ:
if ( virq_is_global(chn->u.virq) ) // 只有全局性虚拟中断才能绑定VCPU
chn->notify_vcpu_id = vcpu_id; // 所谓绑定，不过是设置evtchn中的notify_vcpu_id
else
rc = -EINVAL;
break;
case ECS_UNBOUND:
case ECS_INTERDOMAIN: // 域间绑定之后，状态会被设置为ECS_INTERDOMAIN。
case ECS_PIRQ:
chn->notify_vcpu_id = vcpu_id;
break;
default:
rc = -EINVAL;
break;
}
out:
spin_unlock(&d->event_lock);
return rc;
}
int evtchn_unmask(unsigned int port)
{
struct domain *d = current->domain;
struct vcpu *v;
spin_lock(&d->event_lock);
if ( unlikely(!port_is_valid(d, port)) )
{
spin_unlock(&d->event_lock);
return -EINVAL;
}
v = d->vcpu; // 获得对应的VCPU
/*
* These operations must happen in strict order. Based on
* include/xen/event.h:evtchn_set_pending().
*/
if ( test_and_clear_bit(port, &shared_info(d, evtchn_mask)) && // 如果evtchn_mask被设置，那么取消设置（屏蔽）
test_bit (port, &shared_info(d, evtchn_pending)) && // 并且evtchn_pending被设置（未决）
!test_and_set_bit (port / BITS_PER_EVTCHN_WORD(d), // 那么设置此VCPU里的evtchn_pending_sel
&vcpu_info(v, evtchn_pending_sel)) )
{
vcpu_mark_events_pending(v); // 并且设置此VCPU里的evtchn_upcall_pending
}
spin_unlock(&d->event_lock);
return 0;
}
static long evtchn_reset(evtchn_reset_t *r)
{
domid_t dom = r->dom;
struct domain *d;
int i, rc;
rc = rcu_lock_target_domain_by_id(dom, &d);
if ( rc )
return rc;
rc = xsm_evtchn_reset(current->domain, d);
if ( rc )
goto out;
for ( i = 0; port_is_valid(d, i); i++ )
(void)__evtchn_close(d, i); // 可以这样做的原因是，当初分配port的时候就是严格按照顺序分配的
rc = 0;
out:
rcu_unlock_domain(d);
return rc;
}
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