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math64.h: Add mul_s64_u64_shr()

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This function is needed for KVM's nested virtualization. The nested TSC
scaling implementation requires multiplying the signed TSC offset with
the unsigned TSC multiplier.

Signed-off-by: Ilias Stamatis <ilstam@amazon.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210526184418.28881-2-ilstam@amazon.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Ilias Stamatis 2021-05-26 19:44:08 +01:00 committed by Paolo Bonzini
parent d501f747ef
commit 605a140a49
1 changed files with 19 additions and 0 deletions
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19
include/linux/math64.h
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@ -3,6 +3,7 @@
#define _LINUX_MATH64_H
#include <linux/types.h>
#include <linux/math.h>
#include <vdso/math64.h>
#include <asm/div64.h>
@ -234,6 +235,24 @@ static inline u64 mul_u64_u64_shr(u64 a, u64 b, unsigned int shift)
#endif
#ifndef mul_s64_u64_shr
static inline u64 mul_s64_u64_shr(s64 a, u64 b, unsigned int shift)
{
u64 ret;
/*
* Extract the sign before the multiplication and put it back
* afterwards if needed.
*/
ret = mul_u64_u64_shr(abs(a), b, shift);
if (a < 0)
ret = -((s64) ret);
return ret;
}
#endif /* mul_s64_u64_shr */
#ifndef mul_u64_u32_div
static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 divisor)
{