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: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index cd02f324aa6b39c8ba1d149b7646f356043fa77c..7f7e577a0e39cfca111c5a0b4718480b01c86170 100644 (file)
--- 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 239427ca02af05f8671aacaf9820aa298e94bff1..bab3b9e6f66d0d4919f5f035848037ce5ccf7639 100644 (file)
--- 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);
 }
 
 /*