xen/events: Add the hypervisor interface for the FIFO-based event channels

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

The design document for this new ABI is available here:

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

The ABI is available in Xen 4.4 and later.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

2 files changed, 68 insertions, 6 deletions

diff --git a/include/xen/interface/event_channel.h b/include/xen/interface/event_channel.h
index f4942921e202..7e6acef5415b 100644
--- a/include/xen/interface/event_channel.h
+++ b/include/xen/interface/event_channel.h
@@ -190,6 +190,39 @@ struct evtchn_reset {
 };
 typedef struct evtchn_reset evtchn_reset_t;
 
+/*
+ * EVTCHNOP_init_control: initialize the control block for the FIFO ABI.
+ */
+#define EVTCHNOP_init_control    11
+struct evtchn_init_control {
+	/* IN parameters. */
+	uint64_t control_gfn;
+	uint32_t offset;
+	uint32_t vcpu;
+	/* OUT parameters. */
+	uint8_t link_bits;
+	uint8_t _pad[7];
+};
+
+/*
+ * EVTCHNOP_expand_array: add an additional page to the event array.
+ */
+#define EVTCHNOP_expand_array    12
+struct evtchn_expand_array {
+	/* IN parameters. */
+	uint64_t array_gfn;
+};
+
+/*
+ * EVTCHNOP_set_priority: set the priority for an event channel.
+ */
+#define EVTCHNOP_set_priority    13
+struct evtchn_set_priority {
+	/* IN parameters. */
+	uint32_t port;
+	uint32_t priority;
+};
+
 struct evtchn_op {
 	uint32_t cmd; /* EVTCHNOP_* */
 	union {
@@ -207,4 +240,39 @@ struct evtchn_op {
 };
 DEFINE_GUEST_HANDLE_STRUCT(evtchn_op);
 
+/*
+ * 2-level ABI
+ */
+
+#define EVTCHN_2L_NR_CHANNELS (sizeof(xen_ulong_t) * sizeof(xen_ulong_t) * 64)
+
+/*
+ * FIFO ABI
+ */
+
+/* Events may have priorities from 0 (highest) to 15 (lowest). */
+#define EVTCHN_FIFO_PRIORITY_MAX     0
+#define EVTCHN_FIFO_PRIORITY_DEFAULT 7
+#define EVTCHN_FIFO_PRIORITY_MIN     15
+
+#define EVTCHN_FIFO_MAX_QUEUES (EVTCHN_FIFO_PRIORITY_MIN + 1)
+
+typedef uint32_t event_word_t;
+
+#define EVTCHN_FIFO_PENDING 31
+#define EVTCHN_FIFO_MASKED  30
+#define EVTCHN_FIFO_LINKED  29
+#define EVTCHN_FIFO_BUSY    28
+
+#define EVTCHN_FIFO_LINK_BITS 17
+#define EVTCHN_FIFO_LINK_MASK ((1 << EVTCHN_FIFO_LINK_BITS) - 1)
+
+#define EVTCHN_FIFO_NR_CHANNELS (1 << EVTCHN_FIFO_LINK_BITS)
+
+struct evtchn_fifo_control_block {
+	uint32_t     ready;
+	uint32_t     _rsvd;
+	event_word_t head[EVTCHN_FIFO_MAX_QUEUES];
+};
+
 #endif /* __XEN_PUBLIC_EVENT_CHANNEL_H__ */
diff --git a/include/xen/interface/xen.h b/include/xen/interface/xen.h
index 53ec4167bd0b..0cd5ca333fac 100644
--- a/include/xen/interface/xen.h
+++ b/include/xen/interface/xen.h
@@ -281,12 +281,6 @@ struct multicall_entry {
 };
 DEFINE_GUEST_HANDLE_STRUCT(multicall_entry);
 
-/*
- * Event channel endpoints per domain:
- *  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)
-
 struct vcpu_time_info {
 	/*
 	 * Updates to the following values are preceded and followed