Index: head/share/man/man9/zone.9
===================================================================
--- head/share/man/man9/zone.9
+++ head/share/man/man9/zone.9
@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd January 8, 2020
+.Dd February 4, 2020
 .Dt UMA 9
 .Os
 .Sh NAME
@@ -340,6 +340,10 @@
 See
 .Xr numa 4
 for more details.
+.It Dv UMA_ZONE_CONTIG
+Items in this zone must be contiguous in physical address space.
+Items will follow normal alignment constraints and may span page boundaries
+between pages with contiguous physical addresses.
 .El
 .Pp
 Zones can be destroyed using
@@ -465,12 +469,8 @@
 .Fn uma_zone_set_freef
 functions allow a zone's default slab allocation and free functions to be
 overridden.
-This is useful if the zone's items have special memory allocation constraints.
-For example, if multi-page objects are required to be physically contiguous,
-an
-.Fa allocf
-function which requests contiguous memory from the kernel's page allocator
-may be used.
+This is useful if memory with special constraints such as attributes,
+alignment, or address ranges must be used.
 .Pp
 The
 .Fn uma_zone_set_max
Index: head/sys/vm/uma.h
===================================================================
--- head/sys/vm/uma.h
+++ head/sys/vm/uma.h
@@ -236,6 +236,10 @@
  * overlap when adding new features.
  */
 #define UMA_ZONE_ZINIT		0x0002	/* Initialize with zeros */
+#define UMA_ZONE_CONTIG		0x0004	/*
+					 * Physical memory underlying an object
+					 * must be contiguous.
+					 */
 #define UMA_ZONE_NOTOUCH	0x0008	/* UMA may not access the memory */
 #define UMA_ZONE_MALLOC		0x0010	/* For use by malloc(9) only! */
 #define UMA_ZONE_NOFREE		0x0020	/* Do not free slabs of this type! */
@@ -639,8 +643,7 @@
 #define UMA_SLAB_BOOT	0x01		/* Slab alloced from boot pages */
 #define UMA_SLAB_KERNEL	0x04		/* Slab alloced from kmem */
 #define UMA_SLAB_PRIV	0x08		/* Slab alloced from priv allocator */
-#define UMA_SLAB_OFFP	0x10		/* Slab is managed separately  */
-/* 0x02, 0x40, and 0x80 are available */
+/* 0x02, 0x10, 0x40, and 0x80 are available */
 
 /*
  * Used to pre-fill a zone with some number of items
Index: head/sys/vm/uma_core.c
===================================================================
--- head/sys/vm/uma_core.c
+++ head/sys/vm/uma_core.c
@@ -271,6 +271,7 @@
 static void *page_alloc(uma_zone_t, vm_size_t, int, uint8_t *, int);
 static void *pcpu_page_alloc(uma_zone_t, vm_size_t, int, uint8_t *, int);
 static void *startup_alloc(uma_zone_t, vm_size_t, int, uint8_t *, int);
+static void *contig_alloc(uma_zone_t, vm_size_t, int, uint8_t *, int);
 static void page_free(void *, vm_size_t, uint8_t);
 static void pcpu_page_free(void *, vm_size_t, uint8_t);
 static uma_slab_t keg_alloc_slab(uma_keg_t, uma_zone_t, int, int, int);
@@ -1660,6 +1661,19 @@
 }
 
 /*
+ * Allocate physically contiguous pages.
+ */
+static void *
+contig_alloc(uma_zone_t zone, vm_size_t bytes, int domain, uint8_t *pflag,
+    int wait)
+{
+
+	*pflag = UMA_SLAB_KERNEL;
+	return ((void *)kmem_alloc_contig_domainset(DOMAINSET_FIXED(domain),
+	    bytes, wait, 0, ~(vm_paddr_t)0, 1, 0, VM_MEMATTR_DEFAULT));
+}
+
+/*
  * Frees a number of pages to the system
  *
  * Arguments:
@@ -1679,8 +1693,8 @@
 		return;
 	}
 
-	if ((flags & UMA_SLAB_KERNEL) == 0)
-		panic("UMA: page_free used with invalid flags %x", flags);
+	KASSERT((flags & UMA_SLAB_KERNEL) != 0,
+	    ("UMA: page_free used with invalid flags %x", flags));
 
 	kmem_free((vm_offset_t)mem, size);
 }
@@ -2044,6 +2058,8 @@
 		keg->uk_allocf = startup_alloc;
 	else if (keg->uk_flags & UMA_ZONE_PCPU)
 		keg->uk_allocf = pcpu_page_alloc;
+	else if ((keg->uk_flags & UMA_ZONE_CONTIG) != 0 && keg->uk_ppera > 1)
+		keg->uk_allocf = contig_alloc;
 	else
 		keg->uk_allocf = page_alloc;
 #ifdef UMA_MD_SMALL_ALLOC
@@ -2105,10 +2121,17 @@
 	if ((zone->uz_flags & UMA_ZFLAG_CACHE) != 0)
 		return;
 	KEG_GET(zone, keg);
-	if (keg->uk_flags & UMA_ZONE_PCPU)
-		keg->uk_allocf = pcpu_page_alloc;
-	else if (keg->uk_allocf == startup_alloc)
-		keg->uk_allocf = page_alloc;
+
+	if (keg->uk_allocf == startup_alloc) {
+		/* Switch to the real allocator. */
+		if (keg->uk_flags & UMA_ZONE_PCPU)
+			keg->uk_allocf = pcpu_page_alloc;
+		else if ((keg->uk_flags & UMA_ZONE_CONTIG) != 0 &&
+		    keg->uk_ppera > 1)
+			keg->uk_allocf = contig_alloc;
+		else
+			keg->uk_allocf = page_alloc;
+	}
 }
 
 static void
Index: head/sys/vm/uma_int.h
===================================================================
--- head/sys/vm/uma_int.h
+++ head/sys/vm/uma_int.h
@@ -200,6 +200,7 @@
     "\6NOFREE"				\
     "\5MALLOC"				\
     "\4NOTOUCH"				\
+    "\3CONTIG"				\
     "\2ZINIT"
 
 /*