diff -r aa6ed694499d -r 5f60a383a055 tools/libxc/xc_dom.h
--- a/tools/libxc/xc_dom.h	Sat Apr 03 02:02:05 2010 -0400
+++ b/tools/libxc/xc_dom.h	Sat Apr 03 04:08:44 2010 -0400
@@ -114,6 +114,9 @@
     int (*allocate) (struct xc_dom_image * dom, xen_vaddr_t up_to);
 };
 
+#define XC_DOM_IS_NUMA_GUEST(dom)  \
+    (elf_xen_feature_get(XENFEAT_numa_guest_support, (dom)->parms.f_supported))
+
 /* --- pluggable kernel loader ------------------------------------- */
 
 struct xc_dom_loader {
diff -r aa6ed694499d -r 5f60a383a055 tools/libxc/xc_dom_numa.c
--- a/tools/libxc/xc_dom_numa.c	Sat Apr 03 02:02:05 2010 -0400
+++ b/tools/libxc/xc_dom_numa.c	Sat Apr 03 04:08:44 2010 -0400
@@ -409,7 +409,7 @@
 static int xc_select_domain_vnodes(struct xc_dom_image *dom,
     xc_machine_numa_layout_t *phys_layout, xc_domain_numa_layout_t *pv_layout)
 {
-    int i;
+    int i, numa_split_supported;
     uint32_t page_shift, numa_strategy;
     xen_pfn_t pv_dom_pages;
 
@@ -439,21 +439,24 @@
         return -1; 
     }
 
+    if (!XC_DOM_IS_NUMA_GUEST(dom))
+        xc_dom_printf("%s: Image doesn't support guest numa\n", __FUNCTION__);
+    if (!XC_POWER_OF_2(pv_layout->max_vcpus))
+        xc_dom_printf("%s: #vcpus != 2^n (disable numa split)\n", __FUNCTION__);
+    numa_split_supported = 
+        (XC_DOM_IS_NUMA_GUEST(dom) && XC_POWER_OF_2(pv_layout->max_vcpus));
+
     /* Attempt to confine or split the VM */
     for (i = 1; i <= phys_layout->max_nodes; i<<=1)
     {
         uint64_t vnode_size_pages;
 
         vnode_size_pages = pv_dom_pages/i;
-        if ((vnode_size_pages << page_shift) < XC_VNODE_MIN_SIZE)
-            break;
+        if ((vnode_size_pages << page_shift) < XC_VNODE_MIN_SIZE) break;
 
-        /* Not enough vcpus to distribute over */
-        if (pv_layout->max_vcpus < (i*XC_VCPUS_PER_VNODE))
-            break;
-
-        if ((i > 1) && !XC_POWER_OF_2(pv_layout->max_vcpus))
-            break;
+        if ((i > 1) && !numa_split_supported) break;
+        /* Not enough vcpus to distribute */
+        if (pv_layout->max_vcpus < (i*XC_VCPUS_PER_VNODE)) break;
 
         memset(node_pages_selected, 0, sizeof(node_pages_selected));
         if (!xc_select_best_fit_nodes(phys_layout, i, vnode_size_pages, 
diff -r aa6ed694499d -r 5f60a383a055 xen/common/kernel.c
--- a/xen/common/kernel.c	Sat Apr 03 02:02:05 2010 -0400
+++ b/xen/common/kernel.c	Sat Apr 03 04:08:44 2010 -0400
@@ -244,6 +244,8 @@
                              (1U << XENFEAT_highmem_assist) |
                              (1U << XENFEAT_gnttab_map_avail_bits);
 #endif
+            if (is_numa_domain(current->domain))
+                fi.submap |= (1U << XENFEAT_numa_guest_support);
             break;
         default:
             return -EINVAL;
diff -r aa6ed694499d -r 5f60a383a055 xen/common/libelf/libelf-dominfo.c
--- a/xen/common/libelf/libelf-dominfo.c	Sat Apr 03 02:02:05 2010 -0400
+++ b/xen/common/libelf/libelf-dominfo.c	Sat Apr 03 04:08:44 2010 -0400
@@ -12,7 +12,8 @@
     [XENFEAT_writable_descriptor_tables] = "writable_descriptor_tables",
     [XENFEAT_auto_translated_physmap] = "auto_translated_physmap",
     [XENFEAT_supervisor_mode_kernel] = "supervisor_mode_kernel",
-    [XENFEAT_pae_pgdir_above_4gb] = "pae_pgdir_above_4gb"
+    [XENFEAT_pae_pgdir_above_4gb] = "pae_pgdir_above_4gb",
+    [XENFEAT_numa_guest_support] = "numa_guest_support"
 };
 static const int elf_xen_features =
 sizeof(elf_xen_feature_names) / sizeof(elf_xen_feature_names[0]);
diff -r aa6ed694499d -r 5f60a383a055 xen/include/public/features.h
--- a/xen/include/public/features.h	Sat Apr 03 02:02:05 2010 -0400
+++ b/xen/include/public/features.h	Sat Apr 03 04:08:44 2010 -0400
@@ -68,6 +68,12 @@
  */
 #define XENFEAT_gnttab_map_avail_bits      7
 
+/*
+ * If set, the guest is made aware of the underlying NUMA characteristics
+ * (numa guest enlightenment)
+ */
+#define XENFEAT_numa_guest_support      8
+
 #define XENFEAT_NR_SUBMAPS 1
 
 #endif /* __XEN_PUBLIC_FEATURES_H__ */
diff -r aa6ed694499d -r 5f60a383a055 xen/include/xen/sched.h
--- a/xen/include/xen/sched.h	Sat Apr 03 02:02:05 2010 -0400
+++ b/xen/include/xen/sched.h	Sat Apr 03 04:08:44 2010 -0400
@@ -347,6 +347,7 @@
 #define put_domain(_d) \
   if ( atomic_dec_and_test(&(_d)->refcnt) ) domain_destroy(_d)
 
+#define is_numa_domain(d) ((d)->numa_layout != NULL)
 /*
  * Use this when you don't have an existing reference to @d. It returns
  * FALSE if @d is being destroyed.