[Xen-devel] [PATCH V2 03/15] Add evtchn_level in struct domain

[Wei Liu <wei.liu2@xxxxxxxxxx>]

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

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

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

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

Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 xen/common/event_channel.c |    1 +
 xen/include/xen/event.h    |   16 +++++++++++++++-
 xen/include/xen/sched.h    |    1 +
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index 3293f91..43ee854 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -1180,6 +1180,7 @@ int evtchn_init(struct domain *d)
     clear_page(d->evtchn);
 
     spin_lock_init(&d->event_lock);
+    d->evtchn_level = EVTCHN_DEFAULT_LEVEL;
     if ( get_free_port(d) != 0 ) {
         free_xenheap_page(d->evtchn);
         return -EINVAL;
diff --git a/xen/include/xen/event.h b/xen/include/xen/event.h
index a1574ea..b32b06f 100644
--- a/xen/include/xen/event.h
+++ b/xen/include/xen/event.h
@@ -20,7 +20,21 @@
 #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)
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 45ad6bd..2f18fe5 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -217,6 +217,7 @@ struct domain
     /* Event channel information. */
     struct evtchn  **evtchn;
     spinlock_t       event_lock;
+    unsigned int     evtchn_level;
 
     struct grant_table *grant_table;
 
-- 
1.7.10.4


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