x86: pvclock: create helper for pvclock data retrieval

Originally from Jeremy Fitzhardinge.

So code can be reused.

Acked-by: Glauber Costa <glommer@parallels.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index c59cc97fe6c1..47e25d464104 100644
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -56,4 +56,32 @@ static inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
         return product;
 }
 
+static __always_inline
+u64 pvclock_get_nsec_offset(const struct pvclock_vcpu_time_info *src)
+{
+        u64 delta = __native_read_tsc() - src->tsc_timestamp;
+        return pvclock_scale_delta(delta, src->tsc_to_system_mul,
+                                   src->tsc_shift);
+}
+
+static __always_inline
+unsigned __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src,
+                               cycle_t *cycles, u8 *flags)
+{
+        unsigned version;
+        cycle_t ret, offset;
+        u8 ret_flags;
+
+        version = src->version;
+        rdtsc_barrier();
+        offset = pvclock_get_nsec_offset(src);
+        ret = src->system_time + offset;
+        ret_flags = src->flags;
+        rdtsc_barrier();
+
+        *cycles = ret;
+        *flags = ret_flags;
+        return version;
+}
+
 #endif /* _ASM_X86_PVCLOCK_H */