Index: head/stand/common/help.common
===================================================================
--- head/stand/common/help.common
+++ head/stand/common/help.common
@@ -99,6 +99,13 @@
 	List loaded modules. If [-v] is specified, print more details.
 
 ################################################################################
+# Tmap-vdisk DMap virtual disk
+
+	map-vdisk filename
+
+	Map file as virtual disk.
+
+################################################################################
 # Tmore DPage files
 
 	more <filename> [<filename> ...]
@@ -395,6 +402,13 @@
 	unload
 
 	This command removes any kernel and all loaded modules from memory.
+
+################################################################################
+# Tunmap-vdisk DUnmap virtual disk
+
+	unmap-vdisk diskname
+
+	Delete virtual disk mapping.
 
 ################################################################################
 # Tunset DUnset a variable
Index: head/stand/common/vdisk.c
===================================================================
--- head/stand/common/vdisk.c
+++ head/stand/common/vdisk.c
@@ -0,0 +1,417 @@
+/*-
+ * Copyright 2019 Toomas Soome <tsoome@me.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <stand.h>
+#include <stdarg.h>
+#include <machine/_inttypes.h>
+#include <bootstrap.h>
+#include <sys/disk.h>
+#include <sys/errno.h>
+#include <sys/queue.h>
+#include <sys/param.h>
+#include <disk.h>
+
+static int vdisk_init(void);
+static int vdisk_strategy(void *, int, daddr_t, size_t, char *, size_t *);
+static int vdisk_open(struct open_file *, ...);
+static int vdisk_close(struct open_file *);
+static int vdisk_ioctl(struct open_file *, u_long, void *);
+static int vdisk_print(int);
+
+struct devsw vdisk_dev = {
+	.dv_name = "vdisk",
+	.dv_type = DEVT_DISK,
+	.dv_init = vdisk_init,
+	.dv_strategy = vdisk_strategy,
+	.dv_open = vdisk_open,
+	.dv_close = vdisk_close,
+	.dv_ioctl = vdisk_ioctl,
+	.dv_print = vdisk_print,
+	.dv_cleanup = NULL
+};
+
+typedef STAILQ_HEAD(vdisk_info_list, vdisk_info) vdisk_info_list_t;
+
+typedef struct vdisk_info
+{
+	STAILQ_ENTRY(vdisk_info)	vdisk_link; /* link in device list */
+	char			*vdisk_path;
+	int			vdisk_unit;
+	int			vdisk_fd;
+	uint64_t		vdisk_size;	/* size in bytes */
+	uint32_t		vdisk_sectorsz;
+	uint32_t		vdisk_open;	/* reference counter */
+} vdisk_info_t;
+
+static vdisk_info_list_t vdisk_list;	/* list of mapped vdisks. */
+
+static vdisk_info_t *
+vdisk_get_info(struct devdesc *dev)
+{
+	vdisk_info_t *vd;
+
+	STAILQ_FOREACH(vd, &vdisk_list, vdisk_link) {
+		if (vd->vdisk_unit == dev->d_unit)
+			return (vd);
+	}
+	return (vd);
+}
+
+COMMAND_SET(map_vdisk, "map-vdisk", "map file as virtual disk", command_mapvd);
+
+static int
+command_mapvd(int argc, char *argv[])
+{
+	vdisk_info_t *vd, *p;
+	struct stat sb;
+
+	if (argc != 2) {
+		printf("usage: %s filename\n", argv[0]);
+		return (CMD_ERROR);
+	}
+
+	STAILQ_FOREACH(vd, &vdisk_list, vdisk_link) {
+		if (strcmp(vd->vdisk_path, argv[1]) == 0) {
+			printf("%s: file %s is already mapped as %s%d\n",
+			    argv[0], argv[1], vdisk_dev.dv_name,
+			    vd->vdisk_unit);
+			return (CMD_ERROR);
+		}
+	}
+
+	if (stat(argv[1], &sb) < 0) {
+		/*
+		 * ENOSYS is really ENOENT because we did try to walk
+		 * through devsw list to try to open this file.
+		 */
+		if (errno == ENOSYS)
+			errno = ENOENT;
+
+		printf("%s: stat failed: %s\n", argv[0], strerror(errno));
+		return (CMD_ERROR);
+	}
+
+	/*
+	 * Avoid mapping small files.
+	 */
+	if (sb.st_size < 1024 * 1024) {
+		printf("%s: file %s is too small.\n", argv[0], argv[1]);
+		return (CMD_ERROR);
+	}
+
+	vd = calloc(1, sizeof (*vd));
+	if (vd == NULL) {
+		printf("%s: out of memory\n", argv[0]);
+		return (CMD_ERROR);
+	}
+	vd->vdisk_path = strdup(argv[1]);
+	if (vd->vdisk_path == NULL) {
+		free (vd);
+		printf("%s: out of memory\n", argv[0]);
+		return (CMD_ERROR);
+	}
+	vd->vdisk_fd = open(vd->vdisk_path, O_RDONLY);
+	if (vd->vdisk_fd < 0) {
+		printf("%s: open failed: %s\n", argv[0], strerror(errno));
+		free(vd->vdisk_path);
+		free(vd);
+		return (CMD_ERROR);
+	}
+
+	vd->vdisk_size = sb.st_size;
+	vd->vdisk_sectorsz = DEV_BSIZE;
+	STAILQ_FOREACH(p, &vdisk_list, vdisk_link) {
+		vdisk_info_t *n;
+		if (p->vdisk_unit == vd->vdisk_unit) {
+			vd->vdisk_unit++;
+			continue;
+		}
+		n = STAILQ_NEXT(p, vdisk_link);
+		if (p->vdisk_unit < vd->vdisk_unit) {
+			if (n == NULL) {
+				/* p is last elem */
+				STAILQ_INSERT_TAIL(&vdisk_list, vd, vdisk_link);
+				break;
+			}
+			if (n->vdisk_unit > vd->vdisk_unit) {
+				/* p < vd < n */
+				STAILQ_INSERT_AFTER(&vdisk_list, p, vd,
+				    vdisk_link);
+				break;
+			}
+			/* else n < vd or n == vd */
+			vd->vdisk_unit++;
+			continue;
+		}
+		/* p > vd only if p is the first element */
+		STAILQ_INSERT_HEAD(&vdisk_list, vd, vdisk_link);
+		break;
+	}
+
+	/* if the list was empty or contiguous */
+	if (p == NULL)
+		STAILQ_INSERT_TAIL(&vdisk_list, vd, vdisk_link);
+
+	printf("%s: file %s is mapped as %s%d\n", argv[0], vd->vdisk_path,
+	    vdisk_dev.dv_name, vd->vdisk_unit);
+	return (CMD_OK);
+}
+
+COMMAND_SET(unmap_vdisk, "unmap-vdisk", "unmap virtual disk", command_unmapvd);
+
+/*
+ * unmap-vdisk vdiskX
+ */
+static int
+command_unmapvd(int argc, char *argv[])
+{
+	size_t len;
+	vdisk_info_t *vd;
+	long unit;
+	char *end;
+
+	if (argc != 2) {
+		printf("usage: %s %sN\n", argv[0], vdisk_dev.dv_name);
+		return (CMD_ERROR);
+	}
+
+	len = strlen(vdisk_dev.dv_name);
+	if (strncmp(vdisk_dev.dv_name, argv[1], len) != 0) {
+		printf("%s: unknown device %s\n", argv[0], argv[1]);
+		return (CMD_ERROR);
+	}
+	errno = 0;
+	unit = strtol(argv[1] + len, &end, 10);
+	if (errno != 0 || (*end != '\0' && strcmp(end, ":") != 0)) {
+		printf("%s: unknown device %s\n", argv[0], argv[1]);
+		return (CMD_ERROR);
+	}
+
+	STAILQ_FOREACH(vd, &vdisk_list, vdisk_link) {
+		if (vd->vdisk_unit == unit)
+			break;
+	}
+
+	if (vd == NULL) {
+		printf("%s: unknown device %s\n", argv[0], argv[1]);
+		return (CMD_ERROR);
+	}
+
+	if (vd->vdisk_open != 0) {
+		printf("%s: %s is in use, unable to unmap.\n",
+		    argv[0], argv[1]);
+		return (CMD_ERROR);
+	}
+
+	STAILQ_REMOVE(&vdisk_list, vd, vdisk_info, vdisk_link);
+	close(vd->vdisk_fd);
+	free(vd->vdisk_path);
+	free(vd);
+	printf("%s (%s) unmapped\n", argv[1], vd->vdisk_path);
+
+	return (CMD_OK);
+}
+
+static int
+vdisk_init(void)
+{
+	STAILQ_INIT(&vdisk_list);
+	return (0);
+}
+
+static int
+vdisk_strategy(void *devdata, int rw, daddr_t blk, size_t size,
+    char *buf, size_t *rsize)
+{
+	struct disk_devdesc *dev;
+	vdisk_info_t *vd;
+	ssize_t rv;
+
+	dev = devdata;
+	if (dev == NULL)
+		return (EINVAL);
+	vd = vdisk_get_info((struct devdesc *)dev);
+	if (vd == NULL)
+		return (EINVAL);
+
+	if (size == 0 || (size % 512) != 0)
+		return (EIO);
+
+	if (dev->dd.d_dev->dv_type == DEVT_DISK) {
+		daddr_t offset;
+
+		offset = dev->d_offset * vd->vdisk_sectorsz;
+		offset /= 512;
+		blk += offset;
+	}
+	if (lseek(vd->vdisk_fd, blk << 9, SEEK_SET) == -1)
+		return (EIO);
+
+	errno = 0;
+	switch (rw & F_MASK) {
+	case F_READ:
+		rv = read(vd->vdisk_fd, buf, size);
+		break;
+	case F_WRITE:
+		rv = write(vd->vdisk_fd, buf, size);
+		break;
+	default:
+		return (ENOSYS);
+	}
+
+	if (errno == 0 && rsize != NULL) {
+		*rsize = rv;
+	}
+	return (errno);
+}
+
+static int
+vdisk_open(struct open_file *f, ...)
+{
+	va_list args;
+	struct disk_devdesc *dev;
+	vdisk_info_t *vd;
+	int rc = 0;
+
+	va_start(args, f);
+	dev = va_arg(args, struct disk_devdesc *);
+	va_end(args);
+	if (dev == NULL)
+		return (EINVAL);
+	vd = vdisk_get_info((struct devdesc *)dev);
+	if (vd == NULL)
+		return (EINVAL);
+
+	if (dev->dd.d_dev->dv_type == DEVT_DISK) {
+		rc = disk_open(dev, vd->vdisk_size, vd->vdisk_sectorsz);
+	}
+	if (rc == 0)
+		vd->vdisk_open++;
+	return (rc);
+}
+
+static int
+vdisk_close(struct open_file *f)
+{
+	struct disk_devdesc *dev;
+	vdisk_info_t *vd;
+
+	dev = (struct disk_devdesc *)(f->f_devdata);
+	if (dev == NULL)
+		return (EINVAL);
+	vd = vdisk_get_info((struct devdesc *)dev);
+	if (vd == NULL)
+		return (EINVAL);
+
+	vd->vdisk_open--;
+	if (dev->dd.d_dev->dv_type == DEVT_DISK)
+		return (disk_close(dev));
+	return (0);
+}
+
+static int
+vdisk_ioctl(struct open_file *f, u_long cmd, void *data)
+{
+	struct disk_devdesc *dev;
+	vdisk_info_t *vd;
+	int rc;
+
+	dev = (struct disk_devdesc *)(f->f_devdata);
+	if (dev == NULL)
+		return (EINVAL);
+	vd = vdisk_get_info((struct devdesc *)dev);
+	if (vd == NULL)
+		return (EINVAL);
+
+	if (dev->dd.d_dev->dv_type == DEVT_DISK) {
+		rc = disk_ioctl(dev, cmd, data);
+		if (rc != ENOTTY)
+			return (rc);
+	}
+
+	switch (cmd) {
+	case DIOCGSECTORSIZE:
+		*(u_int *)data = vd->vdisk_sectorsz;
+		break;
+	case DIOCGMEDIASIZE:
+		*(uint64_t *)data = vd->vdisk_size;
+		break;
+	default:
+		return (ENOTTY);
+	}
+	return (0);
+}
+
+static int
+vdisk_print(int verbose)
+{
+	int ret = 0;
+	vdisk_info_t *vd;
+	char line[80];
+
+	if (STAILQ_EMPTY(&vdisk_list))
+		return (ret);
+
+	printf("%s devices:", vdisk_dev.dv_name);
+	if ((ret = pager_output("\n")) != 0)
+		return (ret);
+
+	STAILQ_FOREACH(vd, &vdisk_list, vdisk_link) {
+		struct disk_devdesc vd_dev;
+
+		if (verbose) {
+			printf("  %s", vd->vdisk_path);
+			if ((ret = pager_output("\n")) != 0)
+				break;
+		}
+		snprintf(line, sizeof(line),
+		    "    %s%d", vdisk_dev.dv_name, vd->vdisk_unit);
+		printf("%s:    %" PRIu64 " X %u blocks", line,
+		    vd->vdisk_size / vd->vdisk_sectorsz,
+		    vd->vdisk_sectorsz);
+		if ((ret = pager_output("\n")) != 0)
+			break;
+
+		vd_dev.dd.d_dev = &vdisk_dev;
+		vd_dev.dd.d_unit = vd->vdisk_unit;
+		vd_dev.d_slice = -1;
+		vd_dev.d_partition = -1;
+
+		ret = disk_open(&vd_dev, vd->vdisk_size, vd->vdisk_sectorsz);
+		if (ret == 0) {
+			ret = disk_print(&vd_dev, line, verbose);
+			disk_close(&vd_dev);
+			if (ret != 0)
+				break;
+		} else {
+			ret = 0;
+		}
+	}
+
+	return (ret);
+}
Index: head/stand/efi/loader/conf.c
===================================================================
--- head/stand/efi/loader/conf.c
+++ head/stand/efi/loader/conf.c
@@ -33,11 +33,14 @@
 #include <efilib.h>
 #include <efizfs.h>
 
+extern struct devsw vdisk_dev;
+
 struct devsw *devsw[] = {
 	&efipart_fddev,
 	&efipart_cddev,
 	&efipart_hddev,
 	&efinet_dev,
+	&vdisk_dev,
 #ifdef EFI_ZFS_BOOT
 	&zfs_dev,
 #endif
Index: head/stand/i386/loader/conf.c
===================================================================
--- head/stand/i386/loader/conf.c
+++ head/stand/i386/loader/conf.c
@@ -48,6 +48,7 @@
 #if defined(LOADER_FIREWIRE_SUPPORT)
 extern struct devsw fwohci;
 #endif
+extern struct devsw vdisk_dev;
 
 /* Exported for libstand */
 struct devsw *devsw[] = {
@@ -60,6 +61,7 @@
 #if defined(LOADER_FIREWIRE_SUPPORT)
     &fwohci,
 #endif
+    &vdisk_dev,
 #if defined(LOADER_ZFS_SUPPORT)
     &zfs_dev,
 #endif
Index: head/stand/loader.mk
===================================================================
--- head/stand/loader.mk
+++ head/stand/loader.mk
@@ -31,7 +31,7 @@
 .endif
 
 .if ${LOADER_DISK_SUPPORT:Uyes} == "yes"
-SRCS+=	disk.c part.c
+SRCS+=	disk.c part.c vdisk.c
 .endif
 
 .if ${LOADER_NET_SUPPORT:Uno} == "yes"