[RFC PATCH V2 03/14] Add evtchn_level in struct domain

[Wei Liu <wei.liu2@citrix.com>]

This field is manipulated by hypervisor only, so if anything goes
wrong, it is a bug.

The default event channel level is 2, which has a two level lookup
structure: a selector in struct vcpu and a shared bitmap in shared
info.

The up coming 3-level event channel utilies a three level lookup
structure: a top level selector and second level selector for every
vcpu, and shared bitmap.

When building a domain, it starts with 2-level event channel, which is
guaranteed to be always supported by the hypervisor. If a domain wants
to use N (>=3) level event channel, it must explicitly issue a
hypercall to setup N level event channel.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
 xen/common/event_channel.c |    1 +
 xen/include/xen/sched.h    |   19 ++++++++++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index 9231eb0..bc5db10 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -1173,6 +1173,7 @@ void notify_via_xen_event_channel(struct domain *ld, int lport)
 int evtchn_init(struct domain *d)
 {
     spin_lock_init(&d->event_lock);
+    d->evtchn_level = EVTCHN_DEFAULT_LEVEL; /* = 2 */
     if ( get_free_port(d) != 0 )
         return -EINVAL;
     evtchn_from_port(d, 0)->state = ECS_RESERVED;
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 39f85d2..aa97407 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -50,7 +50,23 @@ extern struct domain *dom0;
 #else
 #define BITS_PER_EVTCHN_WORD(d) (has_32bit_shinfo(d) ? 32 : BITS_PER_LONG)
 #endif
-#define MAX_EVTCHNS(d) (BITS_PER_EVTCHN_WORD(d) * BITS_PER_EVTCHN_WORD(d))
+
+#define EVTCHN_2_LEVEL       2
+#define EVTCHN_3_LEVEL       3
+#define EVTCHN_DEFAULT_LEVEL EVTCHN_2_LEVEL
+#define MAX_EVTCHNS_L2(d) (BITS_PER_EVTCHN_WORD(d) * BITS_PER_EVTCHN_WORD(d))
+#define MAX_EVTCHNS_L3(d) (MAX_EVTCHNS_L2(d) * BITS_PER_EVTCHN_WORD(d))
+#define MAX_EVTCHNS(d) ({ int __v = 0;          \
+            switch ( d->evtchn_level ) {        \
+            case EVTCHN_2_LEVEL:                \
+                __v = MAX_EVTCHNS_L2(d); break; \
+            case EVTCHN_3_LEVEL:                \
+                __v = MAX_EVTCHNS_L3(d); break; \
+            default:                            \
+                BUG();                          \
+            };                                  \
+            __v;})
+
 #define EVTCHNS_PER_BUCKET 128
 #define NR_EVTCHN_BUCKETS  (NR_EVENT_CHANNELS / EVTCHNS_PER_BUCKET)
 
@@ -262,6 +278,7 @@ struct domain
     /* Event channel information. */
     struct evtchn   *evtchn[NR_EVTCHN_BUCKETS];
     spinlock_t       event_lock;
+    unsigned int     evtchn_level;
 
     struct grant_table *grant_table;
 
-- 
1.7.10.4