Commit 347bb444 authored by Zachary Amsden's avatar Zachary Amsden Committed by Avi Kivity
Browse files

x86: pvclock: Move scale_delta into common header 



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: default avatarZachary Amsden <zamsden@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent ca84d1a2

arch/x86/include/asm/pvclock.h

+38 −0
Original line number Diff line number Diff line
@@ -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 */

arch/x86/kernel/pvclock.c

+2 −1
Original line number Diff line number Diff line
@@ -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);

}



/*