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    Subject[PATCH 09/17] Move scale_delta into common header.
    Date
    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>
    ---
    arch/x86/include/asm/pvclock.h | 38 ++++++++++++++++++++++++++++++++++++++
    arch/x86/kernel/pvclock.c | 3 ++-
    2 files changed, 40 insertions(+), 1 deletions(-)

    diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
    index cd02f32..7f7e577 100644
    --- a/arch/x86/include/asm/pvclock.h
    +++ b/arch/x86/include/asm/pvclock.h
    @@ -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 */
    diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
    index 239427c..bab3b9e 100644
    --- a/arch/x86/kernel/pvclock.c
    +++ b/arch/x86/kernel/pvclock.c
    @@ -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);
    }

    /*
    --
    1.7.1


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