evtchn: add FIFO-based event channel ABI

Add the event channel hypercall sub-ops and the definitions for the
shared data structures for the FIFO-based event channel ABI.

The design document for this new ABI is available here:

http://xenbits.xen.org/people/dvrabel/event-channels-F.pdf

In summary, events are reported using a per-domain shared event array
of event words.  Each event word has PENDING, LINKED and MASKED bits
and a LINK field for pointing to the next event in the event queue.

There are 16 event queues (with different priorities) per-VCPU.

Key advantages of this new ABI include:

- Support for over 100,000 events (2^17).
- 16 different event priorities.
- Improved fairness in event latency through the use of FIFOs.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
index b50bd050ba..8c5697e16c 100644
--- a/xen/include/public/xen.h
+++ b/xen/include/public/xen.h
@@ -552,11 +552,13 @@ struct multicall_entry {
 typedef struct multicall_entry multicall_entry_t;
 DEFINE_XEN_GUEST_HANDLE(multicall_entry_t);
 
+#if __XEN_INTERFACE_VERSION__ < 0x00040400
 /*
- * Event channel endpoints per domain:
+ * Event channel endpoints per domain (when using the 2-level ABI):
  *  1024 if a long is 32 bits; 4096 if a long is 64 bits.
  */
-#define NR_EVENT_CHANNELS (sizeof(xen_ulong_t) * sizeof(xen_ulong_t) * 64)
+#define NR_EVENT_CHANNELS EVTCHN_2L_NR_CHANNELS
+#endif
 
 struct vcpu_time_info {
     /*