pvclock.h

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#ifndef _ASM_X86_PVCLOCK_H
#define _ASM_X86_PVCLOCK_H

#include <linux/clocksource.h>
#include <asm/pvclock-abi.h>

/* some helper functions for xen and kvm pv clock sources */
cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);
void pvclock_set_flags(u8 flags);
unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src);
void pvclock_read_wallclock(struct pvclock_wall_clock *wall,
                struct pvclock_vcpu_time_info *vcpu,
                struct timespec *ts);
void pvclock_resume(void);

/*
 * 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;
#else
    ulong tmp;
#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__ (
        "mulq %[mul_frac] ; shrd $32, %[hi], %[lo]"
        : [lo]"=a"(product),
          [hi]"=d"(tmp)
        : "0"(delta),
          [mul_frac]"rm"((u64)mul_frac));
#else
#error implement me!
#endif

    return product;
}

#endif /* _ASM_X86_PVCLOCK_H */