[v3 03/15] Add cmpxchg16b support for x86-64

[Feng Wu <feng.wu@intel.com>]

This patch adds cmpxchg16b support for x86-64, so software
can perform 128-bit atomic write/read.

Signed-off-by: Feng Wu <feng.wu@intel.com>
---
v3:
Newly added.

 xen/include/asm-x86/x86_64/system.h | 28 ++++++++++++++++++++++++++++
 xen/include/xen/types.h             |  5 +++++
 2 files changed, 33 insertions(+)

diff --git a/xen/include/asm-x86/x86_64/system.h b/xen/include/asm-x86/x86_64/system.h
index 662813a..a910d00 100644
--- a/xen/include/asm-x86/x86_64/system.h
+++ b/xen/include/asm-x86/x86_64/system.h
@@ -6,6 +6,34 @@
                                    (unsigned long)(n),sizeof(*(ptr))))
 
 /*
+ * Atomic 16 bytes compare and exchange.  Compare OLD with MEM, if
+ * identical, store NEW in MEM.  Return the initial value in MEM.
+ * Success is indicated by comparing RETURN with OLD.
+ *
+ * This function can only be called when cpu_has_cx16 is ture.
+ */
+
+static always_inline uint128_t __cmpxchg16b(
+    volatile void *ptr, uint128_t old, uint128_t new)
+{
+    uint128_t prev;
+
+    ASSERT(cpu_has_cx16);
+
+    asm volatile ( "lock; cmpxchg16b %4"
+                   : "=d" (prev.high), "=a" (prev.low)
+                   : "c" (new.high), "b" (new.low),
+                   "m" (*__xg((volatile void *)ptr)),
+                   "0" (old.high), "1" (old.low)
+                   : "memory" );
+
+    return prev;
+}
+
+#define cmpxchg16b(ptr,o,n)                                             \
+    __cmpxchg16b((ptr), *(uint128_t *)(o), *(uint128_t *)(n))
+
+/*
  * This function causes value _o to be changed to _n at location _p.
  * If this access causes a fault then we return 1, otherwise we return 0.
  * If no fault occurs then _o is updated to the value we saw at _p. If this
diff --git a/xen/include/xen/types.h b/xen/include/xen/types.h
index 8596ded..30f8a44 100644
--- a/xen/include/xen/types.h
+++ b/xen/include/xen/types.h
@@ -47,6 +47,11 @@ typedef         __u64           uint64_t;
 typedef         __u64           u_int64_t;
 typedef         __s64           int64_t;
 
+typedef struct {
+        uint64_t low;
+        uint64_t high;
+} uint128_t;
+
 struct domain;
 struct vcpu;
 
-- 
2.1.0