The commit is pushed to "branch-rh7-3.10.0-327.36.1.vz7.19.x-ovz" and will
appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.36.1.vz7.19.3
------>
commit 692d327368aaf386c36ad50695cc75b5c5069853
Author: Denis Plotnikov <[email protected]>
Date: Mon Oct 24 16:07:09 2016 +0400
ms/math64: add function to multiply two u64 numbers with overflow handling
The function added as a part of Hyper-V TSC reference page clock porting
https://jira.sw.ru/browse/PSBM-46245
It was initially introduced in commit
35181e86df97e4223f4a28fb33e2bcf3b73de141
by Haozhong Zhang <[email protected]>
Signed-off-by: Denis Plotnikov <[email protected]>
Reviewed-by: Roman Kagan <[email protected]>
Signed-off-by: "Denis V. Lunev" <[email protected]>
---
include/linux/math64.h | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 51 insertions(+)
diff --git a/include/linux/math64.h b/include/linux/math64.h
index c45c089..44282ec 100644
--- a/include/linux/math64.h
+++ b/include/linux/math64.h
@@ -142,6 +142,13 @@ static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned
int shift)
}
#endif /* mul_u64_u32_shr */
+#ifndef mul_u64_u64_shr
+static inline u64 mul_u64_u64_shr(u64 a, u64 mul, unsigned int shift)
+{
+ return (u64)(((unsigned __int128)a * mul) >> shift);
+}
+#endif /* mul_u64_u64_shr */
+
#else
#ifndef mul_u64_u32_shr
@@ -161,6 +168,50 @@ static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned
int shift)
}
#endif /* mul_u64_u32_shr */
+#ifndef mul_u64_u64_shr
+static inline u64 mul_u64_u64_shr(u64 a, u64 b, unsigned int shift)
+{
+ union {
+ u64 ll;
+ struct {
+#ifdef __BIG_ENDIAN
+ u32 high, low;
+#else
+ u32 low, high;
+#endif
+ } l;
+ } rl, rm, rn, rh, a0, b0;
+ u64 c;
+
+ a0.ll = a;
+ b0.ll = b;
+
+ rl.ll = (u64)a0.l.low * b0.l.low;
+ rm.ll = (u64)a0.l.low * b0.l.high;
+ rn.ll = (u64)a0.l.high * b0.l.low;
+ rh.ll = (u64)a0.l.high * b0.l.high;
+
+ /*
+ * Each of these lines computes a 64-bit intermediate result into "c",
+ * starting at bits 32-95. The low 32-bits go into the result of the
+ * multiplication, the high 32-bits are carried into the next step.
+ */
+ rl.l.high = c = (u64)rl.l.high + rm.l.low + rn.l.low;
+ rh.l.low = c = (c >> 32) + rm.l.high + rn.l.high + rh.l.low;
+ rh.l.high = (c >> 32) + rh.l.high;
+
+ /*
+ * The 128-bit result of the multiplication is in rl.ll and rh.ll,
+ * shift it right and throw away the high part of the result.
+ */
+ if (shift == 0)
+ return rl.ll;
+ if (shift < 64)
+ return (rl.ll >> shift) | (rh.ll << (64 - shift));
+ return rh.ll >> (shift & 63);
+}
+#endif /* mul_u64_u64_shr */
+
#endif
#endif /* _LINUX_MATH64_H */
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