diff --git a/usr.sbin/bhyve/tpm_emul_passthru.c b/usr.sbin/bhyve/tpm_emul_passthru.c
index 9d706dee7120..084d31d5fa9f 100644
--- a/usr.sbin/bhyve/tpm_emul_passthru.c
+++ b/usr.sbin/bhyve/tpm_emul_passthru.c
@@ -1,69 +1,107 @@
 /*-
  * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2023 Beckhoff Automation GmbH & Co. KG
  * Author: Corvin Köhne <corvink@FreeBSD.org>
  */
 
 #include <sys/types.h>
 
 #include <err.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <malloc_np.h>
 #include <stdlib.h>
 #include <unistd.h>
 
 #include "config.h"
 #include "tpm_device.h"
 #include "tpm_emul.h"
 
 struct tpm_passthru {
 	int fd;
 };
 
+struct tpm_resp_hdr {
+	uint16_t tag;
+	uint32_t len;
+	uint32_t errcode;
+} __packed;
+
 static int
 tpm_passthru_init(void **sc, nvlist_t *nvl)
 {
 	struct tpm_passthru *tpm;
 	const char *path;
 	
 	tpm = calloc(1, sizeof(struct tpm_passthru));
 	if (tpm == NULL) {
 		warnx("%s: failed to allocate tpm passthru", __func__);
 		return (ENOMEM);
 	}
 
 	path = get_config_value_node(nvl, "path");
 	tpm->fd = open(path, O_RDWR);
 	if (tpm->fd < 0) {
 		warnx("%s: unable to open tpm device \"%s\"", __func__, path);
 		return (ENOENT);
 	}
 
 	*sc = tpm;
 
 	return (0);
 }
 
+static int
+tpm_passthru_execute_cmd(void *sc, void *cmd, uint32_t cmd_size, void *rsp,
+    uint32_t rsp_size)
+{
+	struct tpm_passthru *tpm;
+	ssize_t len;
+
+	if (rsp_size < (ssize_t)sizeof(struct tpm_resp_hdr)) {
+		warn("%s: rsp_size of %u is too small", __func__, rsp_size);
+		return (EINVAL);
+	}
+
+	tpm = sc;
+
+	len = write(tpm->fd, cmd, cmd_size);
+	if (len != cmd_size) {
+		warn("%s: cmd write failed (bytes written: %zd / %d)", __func__,
+		    len, cmd_size);
+		return (EFAULT);
+	}
+
+	len = read(tpm->fd, rsp, rsp_size);
+	if (len < (ssize_t)sizeof(struct tpm_resp_hdr)) {
+		warn("%s: rsp read failed (bytes read: %zd / %d)", __func__,
+		    len, rsp_size);
+		return (EFAULT);
+	}
+
+	return (0);
+}
+
 static void
 tpm_passthru_deinit(void *sc)
 {
 	struct tpm_passthru *tpm;
 
 	tpm = sc;
 	if (tpm == NULL)
 		return;
 
 	if (tpm->fd >= 0)
 		close(tpm->fd);
 
 	free(tpm);
 }
 
 static const struct tpm_emul tpm_emul_passthru = {
 	.name = "passthru",
 	.init = tpm_passthru_init,
 	.deinit = tpm_passthru_deinit,
+	.execute_cmd = tpm_passthru_execute_cmd,
 };
 TPM_EMUL_SET(tpm_emul_passthru);