The following commit has been merged into the x86/asm branch of tip:
Commit-ID: db4e919d9a119b7c54eb5e5ac9bee5d3eb4cb859
Gitweb: https://git.kernel.org/tip/db4e919d9a119b7c54eb5e5ac9bee5d3eb4cb859
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Wed, 28 Aug 2019 17:39:46 +02:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 03 Sep 2019 08:56:14 +02:00
x86/math64: Provide a sane mul_u64_u32_div() implementation for x86_64
On x86_64 we can do a u64 * u64 -> u128 widening multiply followed by
a u128 / u64 -> u64 division to implement a sane version of
mul_u64_u32_div().
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/include/asm/div64.h | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/arch/x86/include/asm/div64.h b/arch/x86/include/asm/div64.h
index 20a4615..9b8cb50 100644
--- a/arch/x86/include/asm/div64.h
+++ b/arch/x86/include/asm/div64.h
@@ -73,6 +73,19 @@ static inline u64 mul_u32_u32(u32 a, u32 b)
#else
# include <asm-generic/div64.h>
+
+static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 div)
+{
+ u64 q;
+
+ asm ("mulq %2; divq %3" : "=a" (q)
+ : "a" (a), "rm" ((u64)mul), "rm" ((u64)div)
+ : "rdx");
+
+ return q;
+}
+#define mul_u64_u32_div mul_u64_u32_div
+
#endif /* CONFIG_X86_32 */
#endif /* _ASM_X86_DIV64_H */
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