diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index 687e39bce3..6438b47b8f 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1663,7 +1663,12 @@ custom_param("tsc", tsc_parse);
 u64 gtime_to_gtsc(struct domain *d, u64 time)
 {
     if ( !is_hvm_domain(d) )
-        time = max_t(s64, time - d->arch.vtsc_offset, 0);
+    {
+        if ( time < d->arch.vtsc_offset )
+            return -scale_delta(d->arch.vtsc_offset - time,
+                                &d->arch.ns_to_vtsc);
+        time -= d->arch.vtsc_offset;
+    }
     return scale_delta(time, &d->arch.ns_to_vtsc);
 }