hv: Add 64 bits hash function

This patch adds hash function to hash 64bit value.

Tracked-On: #4550
Signed-off-by: Yonghua Huang <yonghua.huang@intel.com>
Acked-by: Eddie Dong<eddie.dong@Intel.com>

hypervisor/include/lib/hash.h

@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2020 Intel Corporation. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef HASH_H
+#define HASH_H
+
+#include <types.h>
+
+/*
+ * Hash factor is selected following below formula:
+ *  - factor64 = 2^64 * ((sqrt(5) - 1)/2)
+ * here, ((sqrt(5) - 1)/2) is golden ratio.
+ */
+#define HASH_FACTOR64 0x9E3779B9486E555EUL
+
+/*
+ * Hash function multiplies 64bit key by 64bit hash
+ * factor and returns high bits.
+ *
+ * @pre (bits < 64)
+ */
+static inline uint64_t hash64(uint64_t key, uint32_t bits)
+{
+	return (key * HASH_FACTOR64) >> (64U - bits);
+}
+
+#endif /* HASH_H */