[PATCH] evtchn: simplify sending of notifications

[PATCH] evtchn: simplify sending of notifications

[Jan Beulich]

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The trivial wrapper evtchn_set_pending() is pretty pointless, as it
only serves to invoke another wrapper evtchn_port_set_pending(). In
turn, the latter is kind of inconsistent with its siblings in that is
takes a struct vcpu * rather than a struct domain * - adjusting this
allows for more efficient code in the majority of cases.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -95,8 +95,6 @@ static uint8_t get_xen_consumer(xen_even
 /* Get the notification function for a given Xen-bound event channel. */
 #define xen_notification_fn(e) (xen_consumers[(e)->xen_consumer-1])
 
-static void evtchn_set_pending(struct vcpu *v, int port);
-
 static int virq_is_global(uint32_t virq)
 {
     int rc;
@@ -287,7 +285,7 @@ static long evtchn_bind_interdomain(evtc
      * We may have lost notifications on the remote unbound port. Fix that up
      * here by conservatively always setting a notification on the local port.
      */
-    evtchn_set_pending(ld->vcpu[lchn->notify_vcpu_id], lport);
+    evtchn_port_set_pending(ld, lchn->notify_vcpu_id, lchn);
 
     bind->local_port = lport;
 
@@ -599,11 +597,10 @@ static long evtchn_close(evtchn_close_t 
     return __evtchn_close(current->domain, close->port);
 }
 
-int evtchn_send(struct domain *d, unsigned int lport)
+int evtchn_send(struct domain *ld, unsigned int lport)
 {
     struct evtchn *lchn, *rchn;
-    struct domain *ld = d, *rd;
-    struct vcpu   *rvcpu;
+    struct domain *rd;
     int            rport, ret = 0;
 
     spin_lock(&ld->event_lock);
@@ -633,14 +630,13 @@ int evtchn_send(struct domain *d, unsign
         rd    = lchn->u.interdomain.remote_dom;
         rport = lchn->u.interdomain.remote_port;
         rchn  = evtchn_from_port(rd, rport);
-        rvcpu = rd->vcpu[rchn->notify_vcpu_id];
         if ( consumer_is_xen(rchn) )
-            (*xen_notification_fn(rchn))(rvcpu, rport);
+            xen_notification_fn(rchn)(rd->vcpu[rchn->notify_vcpu_id], rport);
         else
-            evtchn_set_pending(rvcpu, rport);
+            evtchn_port_set_pending(rd, rchn->notify_vcpu_id, rchn);
         break;
     case ECS_IPI:
-        evtchn_set_pending(ld->vcpu[lchn->notify_vcpu_id], lport);
+        evtchn_port_set_pending(ld, lchn->notify_vcpu_id, lchn);
         break;
     case ECS_UNBOUND:
         /* silently drop the notification */
@@ -655,11 +651,6 @@ out:
     return ret;
 }
 
-static void evtchn_set_pending(struct vcpu *v, int port)
-{
-    evtchn_port_set_pending(v, evtchn_from_port(v->domain, port));
-}
-
 int guest_enabled_event(struct vcpu *v, uint32_t virq)
 {
     return ((v != NULL) && (v->virq_to_evtchn[virq] != 0));
@@ -669,6 +660,7 @@ void send_guest_vcpu_virq(struct vcpu *v
 {
     unsigned long flags;
     int port;
+    struct domain *d;
 
     ASSERT(!virq_is_global(virq));
 
@@ -678,7 +670,8 @@ void send_guest_vcpu_virq(struct vcpu *v
     if ( unlikely(port == 0) )
         goto out;
 
-    evtchn_set_pending(v, port);
+    d = v->domain;
+    evtchn_port_set_pending(d, v->vcpu_id, evtchn_from_port(d, port));
 
  out:
     spin_unlock_irqrestore(&v->virq_lock, flags);
@@ -707,7 +700,7 @@ static void send_guest_global_virq(struc
         goto out;
 
     chn = evtchn_from_port(d, port);
-    evtchn_set_pending(d->vcpu[chn->notify_vcpu_id], port);
+    evtchn_port_set_pending(d, chn->notify_vcpu_id, chn);
 
  out:
     spin_unlock_irqrestore(&v->virq_lock, flags);
@@ -731,7 +724,7 @@ void send_guest_pirq(struct domain *d, c
     }
 
     chn = evtchn_from_port(d, port);
-    evtchn_set_pending(d->vcpu[chn->notify_vcpu_id], port);
+    evtchn_port_set_pending(d, chn->notify_vcpu_id, chn);
 }
 
 static struct domain *global_virq_handlers[NR_VIRQS] __read_mostly;
@@ -1202,7 +1195,6 @@ void notify_via_xen_event_channel(struct
 {
     struct evtchn *lchn, *rchn;
     struct domain *rd;
-    int            rport;
 
     spin_lock(&ld->event_lock);
 
@@ -1219,9 +1211,8 @@ void notify_via_xen_event_channel(struct
     if ( likely(lchn->state == ECS_INTERDOMAIN) )
     {
         rd    = lchn->u.interdomain.remote_dom;
-        rport = lchn->u.interdomain.remote_port;
-        rchn  = evtchn_from_port(rd, rport);
-        evtchn_set_pending(rd->vcpu[rchn->notify_vcpu_id], rport);
+        rchn  = evtchn_from_port(rd, lchn->u.interdomain.remote_port);
+        evtchn_port_set_pending(rd, rchn->notify_vcpu_id, rchn);
     }
 
     spin_unlock(&ld->event_lock);
--- a/xen/include/xen/event.h
+++ b/xen/include/xen/event.h
@@ -152,10 +152,11 @@ static inline void evtchn_port_init(stru
         d->evtchn_port_ops->init(d, evtchn);
 }
 
-static inline void evtchn_port_set_pending(struct vcpu *v,
+static inline void evtchn_port_set_pending(struct domain *d,
+                                           unsigned int vcpu_id,
                                            struct evtchn *evtchn)
 {
-    v->domain->evtchn_port_ops->set_pending(v, evtchn);
+    d->evtchn_port_ops->set_pending(d->vcpu[vcpu_id], evtchn);
 }
 
 static inline void evtchn_port_clear_pending(struct domain *d,



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evtchn: simplify sending of notifications

The trivial wrapper evtchn_set_pending() is pretty pointless, as it
only serves to invoke another wrapper evtchn_port_set_pending(). In
turn, the latter is kind of inconsistent with its siblings in that is
takes a struct vcpu * rather than a struct domain * - adjusting this
allows for more efficient code in the majority of cases.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -95,8 +95,6 @@ static uint8_t get_xen_consumer(xen_even
 /* Get the notification function for a given Xen-bound event channel. */
 #define xen_notification_fn(e) (xen_consumers[(e)->xen_consumer-1])
 
-static void evtchn_set_pending(struct vcpu *v, int port);
-
 static int virq_is_global(uint32_t virq)
 {
     int rc;
@@ -287,7 +285,7 @@ static long evtchn_bind_interdomain(evtc
      * We may have lost notifications on the remote unbound port. Fix that up
      * here by conservatively always setting a notification on the local port.
      */
-    evtchn_set_pending(ld->vcpu[lchn->notify_vcpu_id], lport);
+    evtchn_port_set_pending(ld, lchn->notify_vcpu_id, lchn);
 
     bind->local_port = lport;
 
@@ -599,11 +597,10 @@ static long evtchn_close(evtchn_close_t 
     return __evtchn_close(current->domain, close->port);
 }
 
-int evtchn_send(struct domain *d, unsigned int lport)
+int evtchn_send(struct domain *ld, unsigned int lport)
 {
     struct evtchn *lchn, *rchn;
-    struct domain *ld = d, *rd;
-    struct vcpu   *rvcpu;
+    struct domain *rd;
     int            rport, ret = 0;
 
     spin_lock(&ld->event_lock);
@@ -633,14 +630,13 @@ int evtchn_send(struct domain *d, unsign
         rd    = lchn->u.interdomain.remote_dom;
         rport = lchn->u.interdomain.remote_port;
         rchn  = evtchn_from_port(rd, rport);
-        rvcpu = rd->vcpu[rchn->notify_vcpu_id];
         if ( consumer_is_xen(rchn) )
-            (*xen_notification_fn(rchn))(rvcpu, rport);
+            xen_notification_fn(rchn)(rd->vcpu[rchn->notify_vcpu_id], rport);
         else
-            evtchn_set_pending(rvcpu, rport);
+            evtchn_port_set_pending(rd, rchn->notify_vcpu_id, rchn);
         break;
     case ECS_IPI:
-        evtchn_set_pending(ld->vcpu[lchn->notify_vcpu_id], lport);
+        evtchn_port_set_pending(ld, lchn->notify_vcpu_id, lchn);
         break;
     case ECS_UNBOUND:
         /* silently drop the notification */
@@ -655,11 +651,6 @@ out:
     return ret;
 }
 
-static void evtchn_set_pending(struct vcpu *v, int port)
-{
-    evtchn_port_set_pending(v, evtchn_from_port(v->domain, port));
-}
-
 int guest_enabled_event(struct vcpu *v, uint32_t virq)
 {
     return ((v != NULL) && (v->virq_to_evtchn[virq] != 0));
@@ -669,6 +660,7 @@ void send_guest_vcpu_virq(struct vcpu *v
 {
     unsigned long flags;
     int port;
+    struct domain *d;
 
     ASSERT(!virq_is_global(virq));
 
@@ -678,7 +670,8 @@ void send_guest_vcpu_virq(struct vcpu *v
     if ( unlikely(port == 0) )
         goto out;
 
-    evtchn_set_pending(v, port);
+    d = v->domain;
+    evtchn_port_set_pending(d, v->vcpu_id, evtchn_from_port(d, port));
 
  out:
     spin_unlock_irqrestore(&v->virq_lock, flags);
@@ -707,7 +700,7 @@ static void send_guest_global_virq(struc
         goto out;
 
     chn = evtchn_from_port(d, port);
-    evtchn_set_pending(d->vcpu[chn->notify_vcpu_id], port);
+    evtchn_port_set_pending(d, chn->notify_vcpu_id, chn);
 
  out:
     spin_unlock_irqrestore(&v->virq_lock, flags);
@@ -731,7 +724,7 @@ void send_guest_pirq(struct domain *d, c
     }
 
     chn = evtchn_from_port(d, port);
-    evtchn_set_pending(d->vcpu[chn->notify_vcpu_id], port);
+    evtchn_port_set_pending(d, chn->notify_vcpu_id, chn);
 }
 
 static struct domain *global_virq_handlers[NR_VIRQS] __read_mostly;
@@ -1202,7 +1195,6 @@ void notify_via_xen_event_channel(struct
 {
     struct evtchn *lchn, *rchn;
     struct domain *rd;
-    int            rport;
 
     spin_lock(&ld->event_lock);
 
@@ -1219,9 +1211,8 @@ void notify_via_xen_event_channel(struct
     if ( likely(lchn->state == ECS_INTERDOMAIN) )
     {
         rd    = lchn->u.interdomain.remote_dom;
-        rport = lchn->u.interdomain.remote_port;
-        rchn  = evtchn_from_port(rd, rport);
-        evtchn_set_pending(rd->vcpu[rchn->notify_vcpu_id], rport);
+        rchn  = evtchn_from_port(rd, lchn->u.interdomain.remote_port);
+        evtchn_port_set_pending(rd, rchn->notify_vcpu_id, rchn);
     }
 
     spin_unlock(&ld->event_lock);
--- a/xen/include/xen/event.h
+++ b/xen/include/xen/event.h
@@ -152,10 +152,11 @@ static inline void evtchn_port_init(stru
         d->evtchn_port_ops->init(d, evtchn);
 }
 
-static inline void evtchn_port_set_pending(struct vcpu *v,
+static inline void evtchn_port_set_pending(struct domain *d,
+                                           unsigned int vcpu_id,
                                            struct evtchn *evtchn)
 {
-    v->domain->evtchn_port_ops->set_pending(v, evtchn);
+    d->evtchn_port_ops->set_pending(d->vcpu[vcpu_id], evtchn);
 }
 
 static inline void evtchn_port_clear_pending(struct domain *d,

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Re: [PATCH] evtchn: simplify sending of notifications

[David Vrabel]

On 12/01/15 08:57, Jan Beulich wrote:
> The trivial wrapper evtchn_set_pending() is pretty pointless, as it
> only serves to invoke another wrapper evtchn_port_set_pending(). In
> turn, the latter is kind of inconsistent with its siblings in that is
> takes a struct vcpu * rather than a struct domain * - adjusting this
> allows for more efficient code in the majority of cases.

Reviewed-by: David Vrabel <david.vrabel@citrix.com>

David

Re: [PATCH] evtchn: simplify sending of notifications

[Andrew Cooper]

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On 12/01/15 08:57, Jan Beulich wrote:
> --- a/xen/include/xen/event.h
> +++ b/xen/include/xen/event.h
> @@ -152,10 +152,11 @@ static inline void evtchn_port_init(stru
>          d->evtchn_port_ops->init(d, evtchn);
>  }
>  
> -static inline void evtchn_port_set_pending(struct vcpu *v,
> +static inline void evtchn_port_set_pending(struct domain *d,
> +                                           unsigned int vcpu_id,
>                                             struct evtchn *evtchn)

I would rename this to the, now vacant, evtchn_set_pending().  It takes
an evtchn* not a port.  (Its sole caller was evtchn_set_pending(), so
the patch won't grow)

Furthermore, all callers except send_guest_vcpu_virq() currently use
evtchn->notify_vcpu_id to get a struct vcpu* to pass.  I think you can
drop the vcpu_id parameter and use evtchn->notify_vcpu_id directly,
which reduces the likelyhood of a bug where the evtchn is bound to one
vcpu but a caller gets the wrong id and raises the event channel on the
wrong vcpu.

~Andrew

>  {
> -    v->domain->evtchn_port_ops->set_pending(v, evtchn);
> +    d->evtchn_port_ops->set_pending(d->vcpu[vcpu_id], evtchn);
>  }
>  
>  static inline void evtchn_port_clear_pending(struct domain *d,
>
>
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel


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Re: [PATCH] evtchn: simplify sending of notifications

[Jan Beulich]

>>> On 12.01.15 at 12:33, <andrew.cooper3@citrix.com> wrote:
> On 12/01/15 08:57, Jan Beulich wrote:
>> --- a/xen/include/xen/event.h
>> +++ b/xen/include/xen/event.h
>> @@ -152,10 +152,11 @@ static inline void evtchn_port_init(stru
>>          d->evtchn_port_ops->init(d, evtchn);
>>  }
>>  
>> -static inline void evtchn_port_set_pending(struct vcpu *v,
>> +static inline void evtchn_port_set_pending(struct domain *d,
>> +                                           unsigned int vcpu_id,
>>                                             struct evtchn *evtchn)
> 
> I would rename this to the, now vacant, evtchn_set_pending().  It takes
> an evtchn* not a port.  (Its sole caller was evtchn_set_pending(), so
> the patch won't grow)

No (and I had actually considered it) - that would get its name out of
sync with all its sibling wrappers.

> Furthermore, all callers except send_guest_vcpu_virq() currently use
> evtchn->notify_vcpu_id to get a struct vcpu* to pass.  I think you can
> drop the vcpu_id parameter and use evtchn->notify_vcpu_id directly,
> which reduces the likelyhood of a bug where the evtchn is bound to one
> vcpu but a caller gets the wrong id and raises the event channel on the
> wrong vcpu.

Generally a nice idea, but it doesn't immediately/obviously fit with
the use in send_guest_vcpu_virq().

Jan

Re: [PATCH] evtchn: simplify sending of notifications

[Andrew Cooper]

On 12/01/15 11:42, Jan Beulich wrote:
>>>> On 12.01.15 at 12:33, <andrew.cooper3@citrix.com> wrote:
>> On 12/01/15 08:57, Jan Beulich wrote:
>>> --- a/xen/include/xen/event.h
>>> +++ b/xen/include/xen/event.h
>>> @@ -152,10 +152,11 @@ static inline void evtchn_port_init(stru
>>>          d->evtchn_port_ops->init(d, evtchn);
>>>  }
>>>  
>>> -static inline void evtchn_port_set_pending(struct vcpu *v,
>>> +static inline void evtchn_port_set_pending(struct domain *d,
>>> +                                           unsigned int vcpu_id,
>>>                                             struct evtchn *evtchn)
>> I would rename this to the, now vacant, evtchn_set_pending().  It takes
>> an evtchn* not a port.  (Its sole caller was evtchn_set_pending(), so
>> the patch won't grow)
> No (and I had actually considered it) - that would get its name out of
> sync with all its sibling wrappers.

Ah yes - consistency is more important than correctness here.

>
>> Furthermore, all callers except send_guest_vcpu_virq() currently use
>> evtchn->notify_vcpu_id to get a struct vcpu* to pass.  I think you can
>> drop the vcpu_id parameter and use evtchn->notify_vcpu_id directly,
>> which reduces the likelyhood of a bug where the evtchn is bound to one
>> vcpu but a caller gets the wrong id and raises the event channel on the
>> wrong vcpu.
> Generally a nice idea, but it doesn't immediately/obviously fit with
> the use in send_guest_vcpu_virq().

It is awkward that some of the virqs will get delivered on an arbitrary
vcpu, especially as the virq API requires the binding domain to choose a
destination vcpu.  Either way, this is not something to be addressed in
a cleanup patch.

Therefore the original patch is Reviewed-by: Andrew Cooper
<andrew.cooper3@citrix.com>

~Andrew