diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index b3d6e32..ede3fde 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -52,6 +52,15 @@ restore_all_guest:
         movq  8(%rsp),%rcx            # RIP
         movq  24(%rsp),%r11           # RFLAGS
         movq  32(%rsp),%rsp           # RSP
+
+        cmp  $135792468, %rax      # IF this is dummy hvc
+   jne orig_out
+   rdtsc
+   shl  $0x20, %rdx
+   OR   %rax, %rdx
+   movq $135792469, %rax
+
+orig_out:
         je    1f
         sysretq
 1:      sysretl
@@ -120,6 +129,14 @@ restore_all_xen:
  * the space left by the trampoline.
  */
 ENTRY(syscall_enter)
+        cmp  $39, %rax     # IF this is dummy hvc
+   jne orig_syscall_enter
+   rdtsc
+   shl  $0x20, %rdx
+   OR   %rax, %rdx
+   movq $39, %rax
+
+orig_syscall_enter:
         sti
         movl  $FLAT_KERNEL_SS,24(%rsp)
         pushq %rcx
@@ -772,6 +789,7 @@ ENTRY(hypercall_table)
         .quad do_domctl
         .quad do_kexec_op
         .quad do_tmem_op
+   .quad do_dummy_hyp          /* 39 */
         .rept __HYPERVISOR_arch_0-((.-hypercall_table)/8)
         .quad do_ni_hypercall
         .endr
@@ -821,6 +839,7 @@ ENTRY(hypercall_args_table)
         .BYTE 1 /* do_domctl            */
         .BYTE 2 /* do_kexec             */
         .BYTE 1 /* do_tmem_op           */
+        .BYTE 0 /* do_dummy_hyp        */
         .rept __HYPERVISOR_arch_0-(.-hypercall_args_table)
         .BYTE 0 /* do_ni_hypercall      */
         .endr