Index: sys/boot/ofw/libofw/ofw_disk.c
===================================================================
--- sys/boot/ofw/libofw/ofw_disk.c
+++ sys/boot/ofw/libofw/ofw_disk.c
@@ -37,6 +37,7 @@
 #include <machine/stdarg.h>
 
 #include <stand.h>
+#include <sys/disk.h>
 
 #include "bootstrap.h"
 #include "libofw.h"
@@ -154,11 +155,26 @@
 }
 
 static int
-ofwd_ioctl(struct open_file *f __unused, u_long cmd __unused,
-    void *data __unused)
+ofwd_ioctl(struct open_file *f, u_long cmd, void *data)
 {
+	struct ofw_devdesc *dev = f->f_devdata;
+	int block_size;
+	unsigned int n;
 
-	return (EINVAL);
+	switch (cmd) {
+	case DIOCGSECTORSIZE:
+		block_size = OF_block_size(dev->d_handle);
+		*(u_int *)data = block_size;
+		break;
+	case DIOCGMEDIASIZE:
+		block_size = OF_block_size(dev->d_handle);
+		n = OF_blocks(dev->d_handle);
+		*(uint64_t *)data = (uint64_t)(n * block_size);
+		break;
+	default:
+		return (ENOTTY);
+	}
+	return (0);
 }
 
 static int
Index: sys/boot/ofw/libofw/openfirm.h
===================================================================
--- sys/boot/ofw/libofw/openfirm.h
+++ sys/boot/ofw/libofw/openfirm.h
@@ -105,6 +105,8 @@
 int		OF_read(ihandle_t, void *, int);
 int		OF_write(ihandle_t, void *, int);
 int		OF_seek(ihandle_t, u_quad_t);
+unsigned int	OF_blocks(ihandle_t);
+int		OF_block_size(ihandle_t);
 
 /* Memory functions */
 void 		*OF_claim(void *, u_int, u_int);
Index: sys/boot/ofw/libofw/openfirm.c
===================================================================
--- sys/boot/ofw/libofw/openfirm.c
+++ sys/boot/ofw/libofw/openfirm.c
@@ -622,6 +622,53 @@
 	return (args.status);
 }
 
+/* Blocks. */
+unsigned int
+OF_blocks(ihandle_t instance)
+{
+	static struct {
+		cell_t name;
+		cell_t nargs;
+		cell_t nreturns;
+		cell_t instance;
+		cell_t result;
+		cell_t blocks;
+	} args = {
+		(cell_t)"#blocks",
+		2,
+		1,
+	};
+
+	args.instance = instance;
+	if (openfirmware(&args) == -1)
+		return ((unsigned int)-1);
+	return (args.blocks);
+}
+
+/* Block size. */
+int
+OF_block_size(ihandle_t instance)
+{
+	static struct {
+		cell_t name;
+		cell_t nargs;
+		cell_t nreturns;
+		cell_t instance;
+		cell_t result;
+		cell_t size;
+	} args = {
+		(cell_t)"block-size",
+		2,
+		1,
+	};
+
+	args.instance = instance;
+	if (openfirmware(&args) == -1)
+		return (512);
+	return (args.size);
+}
+
+/* 
 /*
  * Memory functions
  */
Index: sys/boot/sparc64/loader/main.c
===================================================================
--- sys/boot/sparc64/loader/main.c
+++ sys/boot/sparc64/loader/main.c
@@ -735,6 +735,16 @@
 }
 
 #ifdef LOADER_ZFS_SUPPORT
+
+/* Set by sparc64_zfs_probe to provide partition size. */
+static size_t part_size;
+
+uint64_t
+ldi_get_size(void *priv __unused)
+{
+	return ((uint64_t)part_size);
+}
+
 static void
 sparc64_zfs_probe(void)
 {
@@ -742,13 +752,11 @@
 	char alias[64], devname[sizeof(alias) + sizeof(":x") - 1];
 	char type[sizeof("device_type")];
 	char *bdev, *dev, *odev;
-	uint64_t guid;
+	uint64_t guid, *guidp;
 	int fd, len, part;
 	phandle_t aliases, options;
 
-	/* Get the GUID of the ZFS pool on the boot device. */
 	guid = 0;
-	zfs_probe_dev(bootpath, &guid);
 
 	/*
 	 * Get the GUIDs of the ZFS pools on any additional disks listed in
@@ -771,12 +779,6 @@
 			continue;
 		strcpy(alias, dev);
 		(void)OF_getprop(aliases, dev, alias, sizeof(alias));
-		/*
-		 * Don't probe the boot disk twice.  Note that bootpath
-		 * includes the partition specifier.
-		 */
-		if (strncmp(alias, bootpath, strlen(alias)) == 0)
-			continue;
 		if (OF_getprop(OF_finddevice(alias), "device_type", type,
 		    sizeof(type)) == -1)
 			continue;
@@ -798,8 +800,14 @@
 			if (part == 2 || vtoc.part[part].tag !=
 			    VTOC_TAG_FREEBSD_ZFS)
 				continue;
+			part_size = vtoc.map[part].nblks;
 			(void)sprintf(devname, "%s:%c", alias, part + 'a');
-			if (zfs_probe_dev(devname, NULL) == ENXIO)
+			/* Get the GUID of the ZFS pool on the boot device. */
+			if (strcmp(devname, bootpath) == 0)
+				guidp = &guid;
+			else
+				guidp = NULL;
+			if (zfs_probe_dev(devname, guidp) == ENXIO)
 				break;
 		}
 	}
Index: sys/boot/userboot/userboot/main.c
===================================================================
--- sys/boot/userboot/userboot/main.c
+++ sys/boot/userboot/userboot/main.c
@@ -31,6 +31,7 @@
 #include <stand.h>
 #include <string.h>
 #include <setjmp.h>
+#include <sys/disk.h>
 
 #include "bootstrap.h"
 #include "disk.h"
@@ -270,6 +271,16 @@
 
 	return (CMD_OK);
 }
+
+uint64_t
+ldi_get_size(void *priv)
+{
+	int fd = (uintptr_t) priv;
+	uint64_t size;
+
+	ioctl(fd, DIOCGMEDIASIZE, &size);
+	return (size);
+}
 #endif /* USERBOOT_ZFS_SUPPORT */
 
 COMMAND_SET(quit, "quit", "exit the loader", command_quit);
Index: sys/boot/userboot/userboot/userboot_disk.c
===================================================================
--- sys/boot/userboot/userboot/userboot_disk.c
+++ sys/boot/userboot/userboot/userboot_disk.c
@@ -91,8 +91,8 @@
 			return (ENOMEM);
 		for (i = 0; i < userdisk_maxunit; i++) {
 			if (CALLBACK(diskioctl, i, DIOCGSECTORSIZE,
-			    &sectorsize) != NULL || CALLBACK(diskioctl, i,
-			    DIOCGMEDIASIZE, &mediasize) != NULL)
+			    &sectorsize) != 0 || CALLBACK(diskioctl, i,
+			    DIOCGMEDIASIZE, &mediasize) != 0)
 				return (ENXIO);
 			ud_info[i].mediasize = mediasize;
 			ud_info[i].sectorsize = sectorsize;
@@ -230,7 +230,12 @@
 userdisk_ioctl(struct open_file *f, u_long cmd, void *data)
 {
 	struct disk_devdesc *dev;
+	int rc;
 
 	dev = (struct disk_devdesc *)f->f_devdata;
+	rc = disk_ioctl(dev, cmd, data);
+	if (rc != ENOTTY)
+		return (rc);
+
 	return (CALLBACK(diskioctl, dev->d_unit, cmd, data));
 }