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x86: pvclock: Move scale_delta into common header

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The scale_delta function for shift / multiply with 31-bit
precision moves to a common header so it can be used by both
kernel and kvm module.

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Zachary Amsden 2010-08-19 22:07:29 -10:00 committed by Avi Kivity
parent ca84d1a24c
commit 347bb4448c
2 changed files with 40 additions and 1 deletions
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38
arch/x86/include/asm/pvclock.h
View File

@ -12,4 +12,42 @@ void pvclock_read_wallclock(struct pvclock_wall_clock *wall,
struct pvclock_vcpu_time_info *vcpu,
struct timespec *ts);
/*
* Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
* yielding a 64-bit result.
*/
static inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
{
u64 product;
#ifdef __i386__
u32 tmp1, tmp2;
#endif
if (shift < 0)
delta >>= -shift;
else
delta <<= shift;
#ifdef __i386__
__asm__ (
"mul %5 ; "
"mov %4,%%eax ; "
"mov %%edx,%4 ; "
"mul %5 ; "
"xor %5,%5 ; "
"add %4,%%eax ; "
"adc %5,%%edx ; "
: "=A" (product), "=r" (tmp1), "=r" (tmp2)
: "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
#elif defined(__x86_64__)
__asm__ (
"mul %%rdx ; shrd $32,%%rdx,%%rax"
: "=a" (product) : "0" (delta), "d" ((u64)mul_frac) );
#else
#error implement me!
#endif
return product;
}
#endif /* _ASM_X86_PVCLOCK_H */

3
arch/x86/kernel/pvclock.c
View File

@ -82,7 +82,8 @@ static inline u64 scale_delta(u64 delta, u32 mul_frac, int shift)
static u64 pvclock_get_nsec_offset(struct pvclock_shadow_time *shadow)
{
u64 delta = native_read_tsc() - shadow->tsc_timestamp;
return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift);
return pvclock_scale_delta(delta, shadow->tsc_to_nsec_mul,
shadow->tsc_shift);
}
/*