diff -r cb756381087c xen/arch/x86/hvm/asid.c
--- a/xen/arch/x86/hvm/asid.c	Thu Jan 06 19:02:36 2011 +0000
+++ b/xen/arch/x86/hvm/asid.c	Fri Jan 07 10:59:14 2011 +0100
@@ -68,7 +68,7 @@ void hvm_asid_init(int nasids)
      * exist that reference earlier generations on this CPU.
      */
     if ( test_and_set_bool(data->initialised) )
-        return hvm_asid_flush_core();
+        return hvm_asid_flush_core(1);
 
     data->max_asid = nasids - 1;
     data->disabled = (nasids <= 1);
@@ -92,7 +92,7 @@ void hvm_asid_flush_vcpu(struct vcpu *v)
     v->arch.hvm_vcpu.asid_generation = 0;
 }
 
-void hvm_asid_flush_core(void)
+void hvm_asid_flush_core(bool_t force_recycle)
 {
     struct hvm_asid_data *data = &this_cpu(hvm_asid_data);
 
@@ -101,7 +101,8 @@ void hvm_asid_flush_core(void)
 
     if ( likely(++data->core_asid_generation != 0) )
     {
-        data->next_asid = 1;
+        if ( force_recycle )
+            data->next_asid = 1;
         return;
     }
 
@@ -133,7 +134,7 @@ bool_t hvm_asid_handle_vmenter(void)
 
     /* If there are no free ASIDs, need to go to a new generation */
     if ( unlikely(data->next_asid > data->max_asid) )
-        hvm_asid_flush_core();
+        hvm_asid_flush_core(1);
 
     /* Now guaranteed to be a free ASID. */
     curr->arch.hvm_vcpu.asid = data->next_asid++;
diff -r cb756381087c xen/include/asm-x86/hvm/asid.h
--- a/xen/include/asm-x86/hvm/asid.h	Thu Jan 06 19:02:36 2011 +0000
+++ b/xen/include/asm-x86/hvm/asid.h	Fri Jan 07 10:59:14 2011 +0100
@@ -30,8 +30,8 @@ void hvm_asid_init(int nasids);
 /* Invalidate a VCPU's current ASID allocation: forces re-allocation. */
 void hvm_asid_flush_vcpu(struct vcpu *v);
 
-/* Flush all ASIDs on this processor core. */
-void hvm_asid_flush_core(void);
+/* Increase core generation, force ASID recycling when necessary. */
+void hvm_asid_flush_core(bool_t force_recycle);
 
 /* Called before entry to guest context. Checks ASID allocation, returns a
  * boolean indicating whether all ASIDs must be flushed. */
diff -r cb756381087c xen/include/asm-x86/hvm/hvm.h
--- a/xen/include/asm-x86/hvm/hvm.h	Thu Jan 06 19:02:36 2011 +0000
+++ b/xen/include/asm-x86/hvm/hvm.h	Fri Jan 07 10:59:14 2011 +0100
@@ -227,7 +227,7 @@ static inline void hvm_flush_guest_tlbs(
 static inline void hvm_flush_guest_tlbs(void)
 {
     if ( hvm_enabled )
-        hvm_asid_flush_core();
+        hvm_asid_flush_core(0);
 }
 
 void hvm_hypercall_page_initialise(struct domain *d,