Commit db4e919d authored Aug 28, 2019 by Peter Zijlstra Committed by Ingo Molnar Sep 03, 2019

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@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 089cf7f6

arch/x86/include/asm/div64.h

+13 −0

Original line number	Diff line number	Diff line
		@@ -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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