diff --git a/sys/dev/xen/bus/xenpv.c b/sys/dev/xen/bus/xenpv.c
--- a/sys/dev/xen/bus/xenpv.c
+++ b/sys/dev/xen/bus/xenpv.c
@@ -96,6 +96,10 @@
 {
 	int error;
 
+	error = xen_arch_init_physmem(dev);
+	if (error != 0)
+		return (error);
+
 	/*
 	 * Let our child drivers identify any child devices that they
 	 * can find.  Once that is done attach any devices that we
@@ -118,8 +122,20 @@
 	void *virt_addr;
 	int error;
 
-	res = bus_alloc_resource(child, SYS_RES_MEMORY, res_id, LOW_MEM_LIMIT,
-	    ~0, size, RF_ACTIVE | RF_UNMAPPED);
+	res = xen_arch_alloc_physmem(dev, res_id, size);
+	if (res == NULL) {
+		static bool warned = false;
+
+		if (__predict_false(!warned)) {
+			warned = true;
+			device_printf(dev,
+			    "unable to allocate from arch specific routine, "
+			    "fall back to unused memory areas\n");
+		}
+		res = bus_alloc_resource(child, SYS_RES_MEMORY, res_id,
+		    LOW_MEM_LIMIT, ~0, size, RF_ACTIVE | RF_UNMAPPED);
+	}
+
 	if (res == NULL)
 		return (NULL);
 
@@ -150,7 +166,9 @@
 
 	pmap_unmapdev(virt_addr, size);
 	vm_phys_fictitious_unreg_range(phys_addr, phys_addr + size);
-	return (bus_release_resource(child, SYS_RES_MEMORY, res_id, res));
+
+	return (xen_arch_free_physmem(dev, res_id, res) ? 0
+	    : bus_release_resource(child, SYS_RES_MEMORY, res_id, res));
 }
 
 static device_method_t xenpv_methods[] = {
diff --git a/sys/x86/include/xen/xen-os.h b/sys/x86/include/xen/xen-os.h
--- a/sys/x86/include/xen/xen-os.h
+++ b/sys/x86/include/xen/xen-os.h
@@ -97,6 +97,11 @@
 /* (Very) early initialization. */
 void xen_early_init(void);
 
+/* Arch-specific helpers to deal with scratch mapping space. */
+int xen_arch_init_physmem(device_t dev);
+struct resource *xen_arch_alloc_physmem(device_t dev, int *res_id, size_t size);
+bool xen_arch_free_physmem(device_t dev, int res_id, struct resource *res);
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* _MACHINE_X86_XEN_XEN_OS_H_ */
diff --git a/sys/x86/xen/hvm.c b/sys/x86/xen/hvm.c
--- a/sys/x86/xen/hvm.c
+++ b/sys/x86/xen/hvm.c
@@ -33,6 +33,7 @@
 #include <sys/linker.h>
 #include <sys/malloc.h>
 #include <sys/proc.h>
+#include <sys/rman.h>
 #include <sys/smp.h>
 #include <sys/systm.h>
 
@@ -47,6 +48,7 @@
 #include <machine/cpu.h>
 #include <machine/md_var.h>
 #include <machine/metadata.h>
+#include <machine/pc/bios.h>
 #include <machine/smp.h>
 
 #include <x86/apicreg.h>
@@ -548,3 +550,105 @@
 
 	return (regs[0] & XEN_HVM_CPUID_IOMMU_MAPPINGS);
 }
+
+static struct rman mem_rman = {
+    .rm_end = ~0,
+    .rm_type = RMAN_ARRAY,
+    .rm_descr = "Xen unpopulated memory addresses"
+};
+
+int xen_arch_init_physmem(device_t dev)
+{
+	static struct bios_smap smap[128];
+	struct xen_memory_map memmap = {
+		.nr_entries = nitems(smap),
+	};
+	unsigned int i;
+	int error;
+
+	error = rman_init(&mem_rman);
+	if (error != 0)
+		return (error);
+
+	if (!xen_initial_domain())
+		return (0);
+
+	set_xen_guest_handle(memmap.buffer, smap);
+	error = HYPERVISOR_memory_op(XENMEM_memory_map, &memmap);
+	if (error != 0)
+		return (error);
+
+	/*
+	 * Fill with UNUSABLE regions, as it's always fine to use those for
+	 * foreign mappings, they will never be populated.
+	 */
+	for (i = 0; i < memmap.nr_entries; i++) {
+		vm_paddr_t start, end;
+
+		if (smap[i].type != SMAP_TYPE_ACPI_ERROR)
+			continue;
+
+		start = round_page(smap[i].base);
+		end = trunc_page(smap[i].base + smap[i].length - 1);
+
+		if (bootverbose != 0)
+			device_printf(dev,
+			    "scratch mapping region @ [%#lx, %#lx]\n",
+			    start, end);
+
+		error = rman_manage_region(&mem_rman, start, end);
+		if (error != 0)
+			device_printf(dev,
+			    "unable to add scratch region [%#lx, %#lx]: %d\n",
+			    start, end, error);
+	}
+
+	return (0);
+}
+
+struct resource *
+xen_arch_alloc_physmem(device_t dev, int *res_id, size_t size)
+{
+	struct resource *res;
+	int error;
+
+	res = rman_reserve_resource(&mem_rman, 0, ~0, size,
+	    RF_ACTIVE | RF_UNMAPPED, dev);
+	if (res == NULL)
+		return (NULL);
+
+	rman_set_rid(res, *res_id);
+	error = bus_activate_resource(dev, SYS_RES_MEMORY, *res_id, res);
+	if (error != 0) {
+		device_printf(dev, "unable to activate resource: %d\n", error);
+		rman_release_resource(res);
+		return (NULL);
+	}
+
+	return (res);
+}
+
+bool
+xen_arch_free_physmem(device_t dev, int res_id, struct resource *res)
+{
+	int error;
+
+	if (!rman_is_region_manager(res, &mem_rman))
+		return (false);
+
+	if (rman_get_flags(res) & RF_ACTIVE) {
+		error = bus_deactivate_resource(dev, SYS_RES_MEMORY, res_id,
+		    res);
+		if (error != 0) {
+			device_printf(dev,
+			    "unable to deactivate resource: %d\n", error);
+			return (true);
+		}
+	}
+
+	error = rman_release_resource(res);
+	if (error != 0)
+		device_printf(dev, "unable to release resource: %d\n", error);
+
+	return (true);
+}