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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCHv4 3/4] evtchn: use a per-event channel lock for sending events
When sending an event, use a new per-event channel lock to safely
validate the event channel state.
This new lock must be held when changing event channel state. Note
that the event channel lock must also be held when changing state from
ECS_FREE or it will race with a concurrent get_free_port() call.
To avoid having to take the remote event channel locks when sending to
an interdomain event channel, the local and remote channel locks are
both held when binding or closing an interdomain event channel.
This significantly increases the number of events that can be sent
from multiple VCPUs. But struct evtchn increases in size, reducing
the number that fit into a single page to 64 (instead of 128).
Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v3:
- Use port_is_valid in evtchn_send().
- Drop event lock from notify_via_xen_event_channel().
v2:
- Compare channel pointers in double_evtchn_lock().
---
xen/common/event_channel.c | 81 +++++++++++++++++++++++++++++++++++++-------
xen/include/xen/sched.h | 1 +
2 files changed, 69 insertions(+), 13 deletions(-)
diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index 4ee65e6..193e565 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -139,6 +139,7 @@ static struct evtchn *alloc_evtchn_bucket(struct domain *d,
unsigned int port)
return NULL;
}
chn[i].port = port + i;
+ spin_lock_init(&chn[i].lock);
}
return chn;
}
@@ -229,11 +230,15 @@ static long evtchn_alloc_unbound(evtchn_alloc_unbound_t
*alloc)
if ( rc )
goto out;
+ spin_lock(&chn->lock);
+
chn->state = ECS_UNBOUND;
if ( (chn->u.unbound.remote_domid = alloc->remote_dom) == DOMID_SELF )
chn->u.unbound.remote_domid = current->domain->domain_id;
evtchn_port_init(d, chn);
+ spin_unlock(&chn->lock);
+
alloc->port = port;
out:
@@ -244,6 +249,28 @@ static long evtchn_alloc_unbound(evtchn_alloc_unbound_t
*alloc)
}
+static void double_evtchn_lock(struct evtchn *lchn, struct evtchn *rchn)
+{
+ if ( lchn < rchn )
+ {
+ spin_lock(&lchn->lock);
+ spin_lock(&rchn->lock);
+ }
+ else
+ {
+ if ( lchn != rchn )
+ spin_lock(&rchn->lock);
+ spin_lock(&lchn->lock);
+ }
+}
+
+static void double_evtchn_unlock(struct evtchn *lchn, struct evtchn *rchn)
+{
+ spin_unlock(&lchn->lock);
+ if ( lchn != rchn )
+ spin_unlock(&rchn->lock);
+}
+
static long evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind)
{
struct evtchn *lchn, *rchn;
@@ -286,6 +313,8 @@ static long
evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind)
if ( rc )
goto out;
+ double_evtchn_lock(lchn, rchn);
+
lchn->u.interdomain.remote_dom = rd;
lchn->u.interdomain.remote_port = rport;
lchn->state = ECS_INTERDOMAIN;
@@ -301,6 +330,8 @@ static long
evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind)
*/
evtchn_port_set_pending(ld, lchn->notify_vcpu_id, lchn);
+ double_evtchn_unlock(lchn, rchn);
+
bind->local_port = lport;
out:
@@ -341,11 +372,16 @@ static long evtchn_bind_virq(evtchn_bind_virq_t *bind)
ERROR_EXIT(port);
chn = evtchn_from_port(d, port);
+
+ spin_lock(&chn->lock);
+
chn->state = ECS_VIRQ;
chn->notify_vcpu_id = vcpu;
chn->u.virq = virq;
evtchn_port_init(d, chn);
+ spin_unlock(&chn->lock);
+
v->virq_to_evtchn[virq] = bind->port = port;
out:
@@ -372,10 +408,15 @@ static long evtchn_bind_ipi(evtchn_bind_ipi_t *bind)
ERROR_EXIT(port);
chn = evtchn_from_port(d, port);
+
+ spin_lock(&chn->lock);
+
chn->state = ECS_IPI;
chn->notify_vcpu_id = vcpu;
evtchn_port_init(d, chn);
+ spin_unlock(&chn->lock);
+
bind->port = port;
out:
@@ -450,11 +491,15 @@ static long evtchn_bind_pirq(evtchn_bind_pirq_t *bind)
goto out;
}
+ spin_lock(&chn->lock);
+
chn->state = ECS_PIRQ;
chn->u.pirq.irq = pirq;
link_pirq_port(port, chn, v);
evtchn_port_init(d, chn);
+ spin_unlock(&chn->lock);
+
bind->port = port;
#ifdef CONFIG_X86
@@ -575,15 +620,24 @@ static long __evtchn_close(struct domain *d1, int port1,
bool_t guest)
BUG_ON(chn2->state != ECS_INTERDOMAIN);
BUG_ON(chn2->u.interdomain.remote_dom != d1);
+ double_evtchn_lock(chn1, chn2);
+
+ free_evtchn(d1, chn1);
+
chn2->state = ECS_UNBOUND;
chn2->u.unbound.remote_domid = d1->domain_id;
- break;
+
+ double_evtchn_unlock(chn1, chn2);
+
+ goto out;
default:
BUG();
}
+ spin_lock(&chn1->lock);
free_evtchn(d1, chn1);
+ spin_unlock(&chn1->lock);
out:
if ( d2 != NULL )
@@ -610,21 +664,18 @@ int evtchn_send(struct domain *ld, unsigned int lport)
struct domain *rd;
int rport, ret = 0;
- spin_lock(&ld->event_lock);
-
- if ( unlikely(!port_is_valid(ld, lport)) )
- {
- spin_unlock(&ld->event_lock);
+ if ( !port_is_valid(ld, lport) )
return -EINVAL;
- }
lchn = evtchn_from_port(ld, lport);
+ spin_lock(&lchn->lock);
+
/* Guest cannot send via a Xen-attached event channel. */
if ( unlikely(consumer_is_xen(lchn)) )
{
- spin_unlock(&ld->event_lock);
- return -EINVAL;
+ ret = -EINVAL;
+ goto out;
}
ret = xsm_evtchn_send(XSM_HOOK, ld, lchn);
@@ -653,7 +704,7 @@ int evtchn_send(struct domain *ld, unsigned int lport)
}
out:
- spin_unlock(&ld->event_lock);
+ spin_unlock(&lchn->lock);
return ret;
}
@@ -1160,11 +1211,15 @@ int alloc_unbound_xen_event_channel(
if ( rc )
goto out;
+ spin_lock(&chn->lock);
+
chn->state = ECS_UNBOUND;
chn->xen_consumer = get_xen_consumer(notification_fn);
chn->notify_vcpu_id = lvcpu;
chn->u.unbound.remote_domid = remote_domid;
+ spin_unlock(&chn->lock);
+
out:
spin_unlock(&ld->event_lock);
@@ -1184,11 +1239,11 @@ void notify_via_xen_event_channel(struct domain *ld,
int lport)
struct evtchn *lchn, *rchn;
struct domain *rd;
- spin_lock(&ld->event_lock);
-
ASSERT(port_is_valid(ld, lport));
lchn = evtchn_from_port(ld, lport);
+ spin_lock(&lchn->lock);
+
if ( likely(lchn->state == ECS_INTERDOMAIN) )
{
ASSERT(consumer_is_xen(lchn));
@@ -1197,7 +1252,7 @@ void notify_via_xen_event_channel(struct domain *ld, int
lport)
evtchn_port_set_pending(rd, rchn->notify_vcpu_id, rchn);
}
- spin_unlock(&ld->event_lock);
+ spin_unlock(&lchn->lock);
}
void evtchn_check_pollers(struct domain *d, unsigned int port)
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 604d047..44ea92d 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -79,6 +79,7 @@ extern domid_t hardware_domid;
struct evtchn
{
+ spinlock_t lock;
#define ECS_FREE 0 /* Channel is available for use. */
#define ECS_RESERVED 1 /* Channel is reserved. */
#define ECS_UNBOUND 2 /* Channel is waiting to bind to a remote domain. */
--
1.7.10.4
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