Index: sys/geom/part/g_part.c
===================================================================
--- sys/geom/part/g_part.c
+++ sys/geom/part/g_part.c
@@ -143,6 +143,10 @@
 SYSCTL_UINT(_kern_geom_part, OID_AUTO, auto_resize,
     CTLFLAG_RWTUN, &auto_resize, 1,
     "Enable auto resize");
+static u_int allow_nesting = 0;
+SYSCTL_UINT(_kern_geom_part, OID_AUTO, allow_nesting,
+    CTLFLAG_RWTUN, &allow_nesting, 0,
+    "Allow additional levels of nesting");
 
 /*
  * The GEOM partitioning class.
@@ -2271,7 +2275,13 @@
 			return;
 		if (g_handleattr_int(bp, "GEOM::fwsectors", table->gpt_sectors))
 			return;
-		if (g_handleattr_int(bp, "PART::isleaf", table->gpt_isleaf))
+		/*
+		 * allow_nesting overrides "isleaf" to false _unless_ the
+		 * provider offset is zero, since otherwise we would recurse.
+		 */
+		if (g_handleattr_int(bp, "PART::isleaf",
+			table->gpt_isleaf
+			&& (allow_nesting == 0 || entry->gpe_offset == 0)))
 			return;
 		if (g_handleattr_int(bp, "PART::depth", table->gpt_depth))
 			return;
Index: sys/geom/part/g_part_gpt.c
===================================================================
--- sys/geom/part/g_part_gpt.c
+++ sys/geom/part/g_part_gpt.c
@@ -54,6 +54,14 @@
 
 FEATURE(geom_part_gpt, "GEOM partitioning class for GPT partitions support");
 
+SYSCTL_DECL(_kern_geom_part);
+static SYSCTL_NODE(_kern_geom_part, OID_AUTO, gpt, CTLFLAG_RW, 0,
+    "GEOM_PART_GPT GUID Partition Table");
+
+static u_int allow_nesting = 0;
+SYSCTL_UINT(_kern_geom_part_gpt, OID_AUTO, allow_nesting,
+    CTLFLAG_RWTUN, &allow_nesting, 0, "Allow nesting");
+
 CTASSERT(offsetof(struct gpt_hdr, padding) == 92);
 CTASSERT(sizeof(struct gpt_ent) == 128);
 
@@ -653,7 +661,7 @@
 	size_t tblsz;
 
 	/* We don't nest, which means that our depth should be 0. */
-	if (basetable->gpt_depth != 0)
+	if (!allow_nesting && basetable->gpt_depth != 0)
 		return (ENXIO);
 
 	table = (struct g_part_gpt_table *)basetable;
@@ -816,7 +824,7 @@
 	int error, index, pri, res;
 
 	/* We don't nest, which means that our depth should be 0. */
-	if (table->gpt_depth != 0)
+	if (!allow_nesting && table->gpt_depth != 0)
 		return (ENXIO);
 
 	pp = cp->provider;