[Xen-devel] [PATCH 13/16] xen/events: Add the hypervisor interface for the FIFO-based event channels

[David Vrabel <david.vrabel@xxxxxxxxxx>]

From: David Vrabel <david.vrabel@xxxxxxxxxx>

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-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.

The ABI is available in Xen 4.4 and later.

Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
---
 drivers/xen/events/events_2l.c        |    8 ++--
 include/xen/interface/event_channel.h |   67 +++++++++++++++++++++++++++++++++
 include/xen/interface/xen.h           |    6 ---
 3 files changed, 71 insertions(+), 10 deletions(-)

diff --git a/drivers/xen/events/events_2l.c b/drivers/xen/events/events_2l.c
index ecb402a..d7ff917 100644
--- a/drivers/xen/events/events_2l.c
+++ b/drivers/xen/events/events_2l.c
@@ -38,12 +38,12 @@
 /* Find the first set bit in a evtchn mask */
 #define EVTCHN_FIRST_BIT(w) find_first_bit(BM(&(w)), BITS_PER_EVTCHN_WORD)
 
-static DEFINE_PER_CPU(xen_ulong_t [NR_EVENT_CHANNELS/BITS_PER_EVTCHN_WORD],
+static DEFINE_PER_CPU(xen_ulong_t [EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD],
                      cpu_evtchn_mask);
 
 static unsigned evtchn_2l_max_channels(void)
 {
-       return NR_EVENT_CHANNELS;
+       return EVTCHN_2L_NR_CHANNELS;
 }
 
 static void evtchn_2l_bind_to_cpu(struct irq_info *info, unsigned cpu)
@@ -316,7 +316,7 @@ irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
                       i % 8 == 0 ? "\n   " : " ");
 
        printk("\nlocal cpu%d mask:\n   ", cpu);
-       for (i = (NR_EVENT_CHANNELS/BITS_PER_EVTCHN_WORD)-1; i >= 0; i--)
+       for (i = (EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD)-1; i >= 0; i--)
                printk("%0*"PRI_xen_ulong"%s", (int)(sizeof(cpu_evtchn[0])*2),
                       cpu_evtchn[i],
                       i % 8 == 0 ? "\n   " : " ");
@@ -332,7 +332,7 @@ irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
        }
 
        printk("\npending list:\n");
-       for (i = 0; i < NR_EVENT_CHANNELS; i++) {
+       for (i = 0; i < EVTCHN_2L_NR_CHANNELS; i++) {
                if (sync_test_bit(i, BM(sh->evtchn_pending))) {
                        int word_idx = i / BITS_PER_EVTCHN_WORD;
                        printk("  %d: event %d -> irq %d%s%s%s\n",
diff --git a/include/xen/interface/event_channel.h 
b/include/xen/interface/event_channel.h
index f494292..0cd1e73 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 +240,38 @@ 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_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 53ec416..0cd5ca3 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
-- 
1.7.2.5


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