diff --git a/usr.sbin/bhyve/qemu_fwcfg.c b/usr.sbin/bhyve/qemu_fwcfg.c
index 13e21daca7ff..8cb71b819956 100644
--- a/usr.sbin/bhyve/qemu_fwcfg.c
+++ b/usr.sbin/bhyve/qemu_fwcfg.c
@@ -1,193 +1,218 @@
 /*-
  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
  *
  * Copyright (c) 2021 Beckhoff Automation GmbH & Co. KG
  * Author: Corvin Köhne <c.koehne@beckhoff.com>
  */
 
 #include <sys/param.h>
 
 #include <machine/vmm.h>
 
 #include <err.h>
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include "acpi_device.h"
 #include "inout.h"
 #include "qemu_fwcfg.h"
 
 #define QEMU_FWCFG_ACPI_DEVICE_NAME "FWCF"
 #define QEMU_FWCFG_ACPI_HARDWARE_ID "QEMU0002"
 
 #define QEMU_FWCFG_SELECTOR_PORT_NUMBER 0x510
 #define QEMU_FWCFG_SELECTOR_PORT_SIZE 1
 #define QEMU_FWCFG_SELECTOR_PORT_FLAGS IOPORT_F_INOUT
 #define QEMU_FWCFG_DATA_PORT_NUMBER 0x511
 #define QEMU_FWCFG_DATA_PORT_SIZE 1
 #define QEMU_FWCFG_DATA_PORT_FLAGS \
 	IOPORT_F_INOUT /* QEMU v2.4+ ignores writes */
 
 #define QEMU_FWCFG_ARCHITECTURE_MASK 0x0001
 #define QEMU_FWCFG_INDEX_MASK 0x3FFF
 
 #define QEMU_FWCFG_SELECT_READ 0
 #define QEMU_FWCFG_SELECT_WRITE 1
 
 #define QEMU_FWCFG_ARCHITECTURE_GENERIC 0
 #define QEMU_FWCFG_ARCHITECTURE_SPECIFIC 1
 
 #pragma pack(1)
 
 union qemu_fwcfg_selector {
 	struct {
 		uint16_t index : 14;
 		uint16_t writeable : 1;
 		uint16_t architecture : 1;
 	};
 	uint16_t bits;
 };
 
 #pragma pack()
 
 struct qemu_fwcfg_softc {
 	struct acpi_device *acpi_dev;
 
 	uint32_t data_offset;
 	union qemu_fwcfg_selector selector;
 	struct qemu_fwcfg_item items[QEMU_FWCFG_MAX_ARCHS]
 				    [QEMU_FWCFG_MAX_ENTRIES];
 };
 
 static struct qemu_fwcfg_softc fwcfg_sc;
 
 static int
 qemu_fwcfg_selector_port_handler(struct vmctx *const ctx __unused, const int in,
     const int port __unused, const int bytes, uint32_t *const eax,
     void *const arg __unused)
 {
 	if (bytes != sizeof(uint16_t)) {
 		warnx("%s: invalid size (%d) of IO port access", __func__,
 		    bytes);
 		return (-1);
 	}
 
 	if (in) {
 		*eax = htole16(fwcfg_sc.selector.bits);
 		return (0);
 	}
 
 	fwcfg_sc.data_offset = 0;
 	fwcfg_sc.selector.bits = le16toh(*eax);
 
 	return (0);
 }
 
 static int
 qemu_fwcfg_data_port_handler(struct vmctx *const ctx __unused, const int in,
     const int port __unused, const int bytes, uint32_t *const eax,
     void *const arg __unused)
 {
 	if (bytes != sizeof(uint8_t)) {
 		warnx("%s: invalid size (%d) of IO port access", __func__,
 		    bytes);
 		return (-1);
 	}
 
 	if (!in) {
 		warnx("%s: Writes to qemu fwcfg data port aren't allowed",
 		    __func__);
 		return (-1);
 	}
 
 	/* get fwcfg item */
 	struct qemu_fwcfg_item *const item =
 	    &fwcfg_sc.items[fwcfg_sc.selector.architecture]
 			   [fwcfg_sc.selector.index];
 	if (item->data == NULL) {
 		warnx(
 		    "%s: qemu fwcfg item doesn't exist (architecture %s index 0x%x)",
 		    __func__,
 		    fwcfg_sc.selector.architecture ? "specific" : "generic",
 		    fwcfg_sc.selector.index);
 		*eax = 0x00;
 		return (0);
 	} else if (fwcfg_sc.data_offset >= item->size) {
 		warnx(
 		    "%s: qemu fwcfg item read exceeds size (architecture %s index 0x%x size 0x%x offset 0x%x)",
 		    __func__,
 		    fwcfg_sc.selector.architecture ? "specific" : "generic",
 		    fwcfg_sc.selector.index, item->size, fwcfg_sc.data_offset);
 		*eax = 0x00;
 		return (0);
 	}
 
 	/* return item data */
 	*eax = item->data[fwcfg_sc.data_offset];
 	fwcfg_sc.data_offset++;
 
 	return (0);
 }
 
+static int
+qemu_fwcfg_add_item(const uint16_t architecture, const uint16_t index,
+    const uint32_t size, void *const data)
+{
+	/* truncate architecture and index to their desired size */
+	const uint16_t arch = architecture & QEMU_FWCFG_ARCHITECTURE_MASK;
+	const uint16_t idx = index & QEMU_FWCFG_INDEX_MASK;
+
+	/* get pointer to item specified by selector */
+	struct qemu_fwcfg_item *const fwcfg_item = &fwcfg_sc.items[arch][idx];
+
+	/* check if item is already used */
+	if (fwcfg_item->data != NULL) {
+		warnx("%s: qemu fwcfg item exists (architecture %s index 0x%x)",
+		    __func__, arch ? "specific" : "generic", idx);
+		return (-1);
+	}
+
+	/* save data of the item */
+	fwcfg_item->size = size;
+	fwcfg_item->data = data;
+
+	return (0);
+}
+
 static int
 qemu_fwcfg_register_port(const char *const name, const int port, const int size,
     const int flags, const inout_func_t handler)
 {
 	struct inout_port iop;
 
 	bzero(&iop, sizeof(iop));
 	iop.name = name;
 	iop.port = port;
 	iop.size = size;
 	iop.flags = flags;
 	iop.handler = handler;
 
 	return (register_inout(&iop));
 }
 
 int
 qemu_fwcfg_init(struct vmctx *const ctx)
 {
 	int error;
 
 	error = acpi_device_create(&fwcfg_sc.acpi_dev, ctx,
 	    QEMU_FWCFG_ACPI_DEVICE_NAME, QEMU_FWCFG_ACPI_HARDWARE_ID);
 	if (error) {
 		warnx("%s: failed to create ACPI device for QEMU FwCfg",
 		    __func__);
 		goto done;
 	}
 
 	error = acpi_device_add_res_fixed_ioport(fwcfg_sc.acpi_dev,
 	    QEMU_FWCFG_SELECTOR_PORT_NUMBER, 2);
 	if (error) {
 		warnx("%s: failed to add fixed IO port for QEMU FwCfg",
 		    __func__);
 		goto done;
 	}
 
 	/* add handlers for fwcfg ports */
 	if ((error = qemu_fwcfg_register_port("qemu_fwcfg_selector",
 	    QEMU_FWCFG_SELECTOR_PORT_NUMBER, QEMU_FWCFG_SELECTOR_PORT_SIZE,
 	    QEMU_FWCFG_SELECTOR_PORT_FLAGS,
 	    qemu_fwcfg_selector_port_handler)) != 0) {
 		warnx("%s: Unable to register qemu fwcfg selector port 0x%x",
 		    __func__, QEMU_FWCFG_SELECTOR_PORT_NUMBER);
 		goto done;
 	}
 	if ((error = qemu_fwcfg_register_port("qemu_fwcfg_data",
 	    QEMU_FWCFG_DATA_PORT_NUMBER, QEMU_FWCFG_DATA_PORT_SIZE,
 	    QEMU_FWCFG_DATA_PORT_FLAGS, qemu_fwcfg_data_port_handler)) != 0) {
 		warnx("%s: Unable to register qemu fwcfg data port 0x%x",
 		    __func__, QEMU_FWCFG_DATA_PORT_NUMBER);
 		goto done;
 	}
 
 done:
 	if (error) {
 		acpi_device_destroy(fwcfg_sc.acpi_dev);
 	}
 
 	return (error);
 }