diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index 518fc9e47f..49b56fa1a3 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -1245,6 +1245,20 @@ void libxl_mac_copy(libxl_ctx *ctx, libxl_mac *dst, const libxl_mac *src);
  */
 #define LIBXL_HAVE_FN_USING_QMP_ASYNC 1
 
+/*
+ * LIBXL_HAVE_DOMAIN_NEED_MEMORY_CONFIG
+ *
+ * If this is set, libxl_domain_need_memory takes a
+ * libxl_domain_config* (non-const) and uint32_t domid_for_logging
+ * (instead of a const libxl_domain_build_info*).
+ *
+ * If this is set, there is no need to call
+ * libxl_get_required_shadow_memory and instead the caller should
+ * simply leave shadow_memkb set to LIBXL_MEMKB_DEFAULT and allow
+ * libxl to fill in a suitable default in the usual way.
+ */
+#define LIBXL_HAVE_DOMAIN_NEED_MEMORY_CONFIG
+
 typedef char **libxl_string_list;
 void libxl_string_list_dispose(libxl_string_list *sl);
 int libxl_string_list_length(const libxl_string_list *sl);
@@ -1723,8 +1737,13 @@ int libxl_get_memory_target_0x040700(libxl_ctx *ctx, uint32_t domid,
  */
 /* how much free memory in the system a domain needs to be built */
 int libxl_domain_need_memory(libxl_ctx *ctx,
-                             const libxl_domain_build_info *b_info_in,
+                             libxl_domain_config *config
+                             /* ^ will be partially defaulted */,
+                             uint32_t domid_for_logging /* INVALID_DOMID ok */,
                              uint64_t *need_memkb);
+int libxl_domain_need_memory_0x041200(libxl_ctx *ctx,
+                                      const libxl_domain_build_info *b_info_in,
+                                      uint64_t *need_memkb);
 int libxl_domain_need_memory_0x040700(libxl_ctx *ctx,
                                       const libxl_domain_build_info *b_info_in,
                                       uint32_t *need_memkb)
@@ -1754,6 +1773,8 @@ int libxl_wait_for_memory_target(libxl_ctx *ctx, uint32_t domid, int wait_secs);
 #define libxl_get_memory_target libxl_get_memory_target_0x040700
 #define libxl_domain_need_memory libxl_domain_need_memory_0x040700
 #define libxl_get_free_memory libxl_get_free_memory_0x040700
+#elif defined(LIBXL_API_VERSION) && LIBXL_API_VERSION < 0x041300
+#define libxl_domain_need_memory libxl_domain_need_memory_0x041200
 #endif
 
 int libxl_vncviewer_exec(libxl_ctx *ctx, uint32_t domid, int autopass);
diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index c5685b061c..cdb294ab8d 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -140,8 +140,9 @@ static int numa_cmpf(const libxl__numa_candidate *c1,
 
 /* The actual automatic NUMA placement routine */
 static int numa_place_domain(libxl__gc *gc, uint32_t domid,
-                             libxl_domain_build_info *info)
+                             libxl_domain_config *d_config)
 {
+    libxl_domain_build_info *info = &d_config->b_info;
     int found;
     libxl__numa_candidate candidate;
     libxl_bitmap cpumap, cpupool_nodemap, *map;
@@ -195,7 +196,7 @@ static int numa_place_domain(libxl__gc *gc, uint32_t domid,
         }
     }
 
-    rc = libxl_domain_need_memory(CTX, info, &memkb);
+    rc = libxl__domain_need_memory_calculate(gc, info, &memkb);
     if (rc)
         goto out;
     if (libxl_node_bitmap_alloc(CTX, &cpupool_nodemap, 0)) {
@@ -432,7 +433,7 @@ int libxl__build_pre(libxl__gc *gc, uint32_t domid,
             if (rc)
                 return rc;
 
-            rc = numa_place_domain(gc, domid, info);
+            rc = numa_place_domain(gc, domid, d_config);
             if (rc) {
                 libxl_bitmap_dispose(&cpumap_soft);
                 return rc;
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 50ac7b64ed..01de5576d9 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1450,6 +1450,10 @@ _hidden int libxl__domain_build_info_setdefault(libxl__gc *gc,
 _hidden void libxl__rdm_setdefault(libxl__gc *gc,
                                    libxl_domain_build_info *b_info);
 
+_hidden int libxl__domain_need_memory_calculate(libxl__gc *gc,
+                                      libxl_domain_build_info *b_info,
+                                      uint64_t *need_memkb);
+
 _hidden const char *libxl__device_nic_devname(libxl__gc *gc,
                                               uint32_t domid,
                                               uint32_t devid,
diff --git a/tools/libxl/libxl_mem.c b/tools/libxl/libxl_mem.c
index fd6f33312e..6042299393 100644
--- a/tools/libxl/libxl_mem.c
+++ b/tools/libxl/libxl_mem.c
@@ -446,20 +446,12 @@ int libxl_get_memory_target_0x040700(
     return libxl__memkb_64to32(ctx, rc, my_out_target, out_target);
 }
 
-int libxl_domain_need_memory(libxl_ctx *ctx,
-                             const libxl_domain_build_info *b_info_in,
-                             uint64_t *need_memkb)
+int libxl__domain_need_memory_calculate(libxl__gc *gc,
+                              libxl_domain_build_info *b_info,
+                              uint64_t *need_memkb)
 {
-    GC_INIT(ctx);
-    libxl_domain_build_info b_info[1];
     int rc;
 
-    libxl_domain_build_info_init(b_info);
-    libxl_domain_build_info_copy(ctx, b_info, b_info_in);
-
-    rc = libxl__domain_build_info_setdefault(gc, b_info);
-    if (rc) goto out;
-
     *need_memkb = b_info->target_memkb;
     *need_memkb += b_info->shadow_memkb + b_info->iommu_memkb;
 
@@ -481,10 +473,57 @@ int libxl_domain_need_memory(libxl_ctx *ctx,
         *need_memkb += (2 * 1024) - (*need_memkb % (2 * 1024));
     rc = 0;
 out:
-    GC_FREE;
-    libxl_domain_build_info_dispose(b_info);
     return rc;
+}
 
+int libxl_domain_need_memory(libxl_ctx *ctx,
+                             libxl_domain_config *d_config,
+                             uint32_t domid_for_logging,
+                             uint64_t *need_memkb)
+{
+    GC_INIT(ctx);
+    int rc;
+
+    rc = libxl__domain_config_setdefault(gc,
+                                         d_config,
+                                         domid_for_logging);
+    if (rc) goto out;
+
+    rc = libxl__domain_need_memory_calculate(gc,
+                                   &d_config->b_info,
+                                   need_memkb);
+    if (rc) goto out;
+
+    rc = 0;
+ out:
+    GC_FREE;
+    return rc;
+}
+
+int libxl_domain_need_memory_0x041200(libxl_ctx *ctx,
+                                      const libxl_domain_build_info *b_info_in,
+                                      uint64_t *need_memkb)
+{
+    GC_INIT(ctx);
+    int rc;
+
+    libxl_domain_build_info b_info[1];
+    libxl_domain_build_info_init(b_info);
+    libxl_domain_build_info_copy(ctx, b_info, b_info_in);
+
+    rc = libxl__domain_build_info_setdefault(gc, b_info);
+    if (rc) goto out;
+
+    rc = libxl__domain_need_memory_calculate(gc,
+                                   b_info,
+                                   need_memkb);
+    if (rc) goto out;
+
+    rc = 0;
+ out:
+    libxl_domain_build_info_dispose(b_info);
+    GC_FREE;
+    return rc;
 }
 
 int libxl_domain_need_memory_0x040700(libxl_ctx *ctx,
@@ -494,7 +533,7 @@ int libxl_domain_need_memory_0x040700(libxl_ctx *ctx,
     uint64_t my_need_memkb;
     int rc;
 
-    rc = libxl_domain_need_memory(ctx, b_info_in, &my_need_memkb);
+    rc = libxl_domain_need_memory_0x041200(ctx, b_info_in, &my_need_memkb);
     return libxl__memkb_64to32(ctx, rc, my_need_memkb, need_memkb);
 }
 
diff --git a/tools/xl/xl_vmcontrol.c b/tools/xl/xl_vmcontrol.c
index d33c6b38c9..e520b1da79 100644
--- a/tools/xl/xl_vmcontrol.c
+++ b/tools/xl/xl_vmcontrol.c
@@ -322,7 +322,7 @@ static bool freemem(uint32_t domid, libxl_domain_config *d_config)
     if (!autoballoon)
         return true;
 
-    rc = libxl_domain_need_memory(ctx, &d_config->b_info, &need_memkb);
+    rc = libxl_domain_need_memory(ctx, d_config, domid, &need_memkb);
     if (rc < 0)
         return false;