diff -r be52424a543e xen/arch/x86/hvm/vmx/vmcs.c
--- a/xen/arch/x86/hvm/vmx/vmcs.c	Fri Jun 27 14:15:11 2008 +0100
+++ b/xen/arch/x86/hvm/vmx/vmcs.c	Tue Jul 08 22:26:57 2008 +0800
@@ -40,6 +40,7 @@
 
 static int opt_vpid_enabled = 1;
 boolean_param("vpid", opt_vpid_enabled);
+int softtsc = 1;
 
 /* Dynamic (run-time adjusted) execution control flags. */
 u32 vmx_pin_based_exec_control __read_mostly;
@@ -96,6 +97,8 @@
            CPU_BASED_MOV_DR_EXITING |
            CPU_BASED_ACTIVATE_IO_BITMAP |
            CPU_BASED_USE_TSC_OFFSETING);
+    if (softtsc)
+        min |= CPU_BASED_RDTSC_EXITING;
     opt = (CPU_BASED_ACTIVATE_MSR_BITMAP |
            CPU_BASED_TPR_SHADOW |
            CPU_BASED_ACTIVATE_SECONDARY_CONTROLS);
diff -r be52424a543e xen/arch/x86/hvm/vmx/vmx.c
--- a/xen/arch/x86/hvm/vmx/vmx.c	Fri Jun 27 14:15:11 2008 +0100
+++ b/xen/arch/x86/hvm/vmx/vmx.c	Tue Jul 08 22:26:57 2008 +0800
@@ -1375,6 +1375,17 @@
     if ( paging_invlpg(curr, vaddr) )
         vpid_sync_vcpu_gva(curr, vaddr);
 }
+
+static void vmx_rdtsc_intercept(struct cpu_user_regs *regs)
+{
+    uint64_t tsc;
+    struct vcpu *v = current; 
+
+    tsc = hvm_get_guest_tsc(v);
+    regs->eax = tsc & 0xffff;
+    regs->edx = tsc >> 32 & 0xffff;
+}
+
 
 #define CASE_SET_REG(REG, reg)      \
     case VMX_CONTROL_REG_ACCESS_GPR_ ## REG: regs->reg = value; break
@@ -2192,6 +2203,11 @@
         vmx_invlpg_intercept(exit_qualification);
         break;
     }
+    case EXIT_REASON_RDTSC:
+        inst_len = __get_instruction_length();
+        __update_guest_eip(inst_len);
+        vmx_rdtsc_intercept(regs);
+        break;
     case EXIT_REASON_VMCALL:
     {
         int rc;