From: David Vrabel <david.vrabel@citrix.com>
To: xen-devel@lists.xenproject.org
Cc: Keir Fraser <keir@xen.org>, Tim Deegan <tim@xen.org>,
David Vrabel <david.vrabel@citrix.com>,
Jan Beulich <jbeulich@suse.com>,
Ian Campbell <ian.campbell@citrix.com>
Subject: [PATCHv2 3/5] evtchn: use a per-event channel lock for sending events
Date: Mon, 15 Jun 2015 16:48:17 +0100 [thread overview]
Message-ID: <1434383299-21833-4-git-send-email-david.vrabel@citrix.com> (raw)
In-Reply-To: <1434383299-21833-1-git-send-email-david.vrabel@citrix.com>
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.
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@citrix.com>
---
v2:
- Compare channel pointers in double_evtchn_lock().
---
xen/common/event_channel.c | 80 ++++++++++++++++++++++++++++++++++++++------
xen/include/xen/sched.h | 1 +
2 files changed, 70 insertions(+), 11 deletions(-)
diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index fd48646..416c76f 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;
}
@@ -228,11 +229,15 @@ 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:
@@ -243,6 +248,28 @@ 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;
@@ -285,6 +312,8 @@ 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;
@@ -300,6 +329,8 @@ 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:
@@ -340,11 +371,16 @@ 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:
@@ -371,10 +407,15 @@ 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:
@@ -449,11 +490,15 @@ 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
@@ -467,7 +512,6 @@ static long evtchn_bind_pirq(evtchn_bind_pirq_t *bind)
return rc;
}
-
static long __evtchn_close(struct domain *d1, int port1)
{
struct domain *d2 = NULL;
@@ -574,15 +618,24 @@ static long __evtchn_close(struct domain *d1, int port1)
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 )
@@ -609,21 +662,18 @@ 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 ( unlikely(lport >= read_atomic(&ld->valid_evtchns)) )
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);
@@ -652,7 +702,7 @@ int evtchn_send(struct domain *ld, unsigned int lport)
}
out:
- spin_unlock(&ld->event_lock);
+ spin_unlock(&lchn->lock);
return ret;
}
@@ -1163,11 +1213,15 @@ 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);
@@ -1214,6 +1268,8 @@ void notify_via_xen_event_channel(struct domain *ld, int lport)
lchn = evtchn_from_port(ld, lport);
ASSERT(consumer_is_xen(lchn));
+ spin_lock(&lchn->lock);
+
if ( likely(lchn->state == ECS_INTERDOMAIN) )
{
rd = lchn->u.interdomain.remote_dom;
@@ -1221,6 +1277,8 @@ void notify_via_xen_event_channel(struct domain *ld, int lport)
evtchn_port_set_pending(rd, rchn->notify_vcpu_id, rchn);
}
+ spin_unlock(&lchn->lock);
+
spin_unlock(&ld->event_lock);
}
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
next prev parent reply other threads:[~2015-06-15 16:45 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-15 15:48 [PATCHv2 0/5] evtchn: Improve scalebility David Vrabel
2015-06-15 15:48 ` [PATCHv2 1/5] evtchn: factor out freeing an event channel David Vrabel
2015-06-15 15:48 ` [PATCHv2 2/5] evtchn: simplify port_is_valid() David Vrabel
2015-06-15 15:57 ` Ian Campbell
2015-06-15 15:59 ` David Vrabel
2015-06-15 16:09 ` Ian Campbell
2015-06-15 15:48 ` David Vrabel [this message]
2015-06-16 9:18 ` [PATCHv2 3/5] evtchn: use a per-event channel lock for sending events Jan Beulich
2015-06-16 9:34 ` David Vrabel
2015-06-16 9:51 ` Jan Beulich
2015-06-16 9:57 ` David Vrabel
2015-06-16 15:19 ` David Vrabel
2015-06-16 15:58 ` David Vrabel
2015-06-16 16:19 ` Jan Beulich
2015-06-16 16:39 ` David Vrabel
2015-06-17 7:05 ` Jan Beulich
2015-06-16 16:06 ` Jan Beulich
2015-06-15 15:48 ` [PATCHv2 4/5] evtchn: remove the locking when unmasking an event channel David Vrabel
2015-06-16 9:19 ` Jan Beulich
2015-06-16 9:40 ` David Vrabel
2015-06-15 15:48 ` [PATCHv2 5/5] evtchn: pad struct evtchn to 64 bytes David Vrabel
2015-06-16 9:22 ` Jan Beulich
2015-06-16 11:14 ` Julien Grall
2015-06-16 11:59 ` Jan Beulich
2015-06-16 12:57 ` Julien Grall
2015-06-16 13:13 ` David Vrabel
2015-06-16 13:27 ` Julien Grall
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