path: root/meta/recipes-devtools/qemu/qemu/0001-Provide-support-for-the-CUSE-TPM.patch

From 8737eef18f39ed087fd911d0a0886e8174d0468c Mon Sep 17 00:00:00 2001
From: Stefan Berger <stefanb@linux.vnet.ibm.com>
Date: Sat, 31 Dec 2016 11:23:32 -0500
Subject: [PATCH 1/4] Provide support for the CUSE TPM

Rather than integrating TPM functionality into QEMU directly
using the TPM emulation of libtpms, we now integrate an external
emulated TPM device. This device is expected to implement a Linux
CUSE interface (CUSE = character device in userspace).

QEMU talks to the CUSE TPM using much functionality of the
passthrough driver. For example, the TPM commands and responses
are sent to the CUSE TPM using the read()/write() interface.
However, some out-of-band control needs to be done using the CUSE
TPM's ioctls. The CUSE TPM currently defines and implements 15
different ioctls for controlling certain life-cycle aspects of
the emulated TPM. The ioctls can be regarded as a replacement for
direct function calls to a TPM emulator if the TPM were to be
directly integrated into QEMU.

One of the ioctls allows to get a bitmask of supported capabilities.
Each returned bit indicates which capabilities have been implemented.
An include file defining the various ioctls is added to QEMU.

The CUSE TPM and associated tools can be found here:

https://github.com/stefanberger/swtpm

(please use the latest version)

To use the external CUSE TPM, the CUSE TPM should be started as follows:

/usr/bin/swtpm_ioctl -s /dev/vtpm-test

/usr/bin/swtpm_cuse -n vtpm-test

QEMU can then be started using the following parameters:

qemu-system-x86_64 \
	[...] \
        -tpmdev cuse-tpm,id=tpm0,cancel-path=/dev/null,path=/dev/vtpm-test \
        -device tpm-tis,id=tpm0,tpmdev=tpm0 \
	[...]

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Cc: Eric Blake <eblake@redhat.com>

Conflicts:
	docs/qmp-commands.txt

Patch cherry-picked from https://github.com/stefanberger/qemu-tpm, branch v2.8.0+tpm,
commit 27d6cd856d5a14061955df7a93ee490697a7a174. Applied cleanly except for
docs/qmp-commands.txt which did not exist yet in qemu 2.7.

Upstream-Status: Pending [https://lists.nongnu.org/archive/html/qemu-devel/2016-06/msg00252.html]
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
---
 hmp.c                    |   6 ++
 hw/tpm/tpm_int.h         |   1 +
 hw/tpm/tpm_ioctl.h       | 215 +++++++++++++++++++++++++++++++++++++
 hw/tpm/tpm_passthrough.c | 274 +++++++++++++++++++++++++++++++++++++++++++++--
 qapi-schema.json         |  18 +++-
 qemu-options.hx          |  21 +++-
 tpm.c                    |  11 +-
 7 files changed, 529 insertions(+), 17 deletions(-)
 create mode 100644 hw/tpm/tpm_ioctl.h

diff --git a/hmp.c b/hmp.c
index cc2056e9e2..277b45ef5a 100644
--- a/hmp.c
+++ b/hmp.c
@@ -883,6 +883,12 @@ void hmp_info_tpm(Monitor *mon, const QDict *qdict)
                            tpo->has_cancel_path ? ",cancel-path=" : "",
                            tpo->has_cancel_path ? tpo->cancel_path : "");
             break;
+        case TPM_TYPE_OPTIONS_KIND_CUSE_TPM:
+            tpo = ti->options->u.passthrough.data;
+            monitor_printf(mon, "%s%s",
+                           tpo->has_path ? ",path=" : "",
+                           tpo->has_path ? tpo->path : "");
+            break;
         case TPM_TYPE_OPTIONS_KIND__MAX:
             break;
         }
diff --git a/hw/tpm/tpm_int.h b/hw/tpm/tpm_int.h
index f2f285b3cc..6b2c9c953a 100644
--- a/hw/tpm/tpm_int.h
+++ b/hw/tpm/tpm_int.h
@@ -61,6 +61,7 @@ struct tpm_resp_hdr {
 #define TPM_TAG_RSP_AUTH1_COMMAND 0xc5
 #define TPM_TAG_RSP_AUTH2_COMMAND 0xc6
 
+#define TPM_SUCCESS               0
 #define TPM_FAIL                  9
 
 #define TPM_ORD_ContinueSelfTest  0x53
diff --git a/hw/tpm/tpm_ioctl.h b/hw/tpm/tpm_ioctl.h
new file mode 100644
index 0000000000..a341e15741
--- /dev/null
+++ b/hw/tpm/tpm_ioctl.h
@@ -0,0 +1,215 @@
+/*
+ * tpm_ioctl.h
+ *
+ * (c) Copyright IBM Corporation 2014, 2015.
+ *
+ * This file is licensed under the terms of the 3-clause BSD license
+ */
+#ifndef _TPM_IOCTL_H_
+#define _TPM_IOCTL_H_
+
+#include <stdint.h>
+#include <sys/uio.h>
+#include <sys/types.h>
+#include <sys/ioctl.h>
+
+/*
+ * Every response from a command involving a TPM command execution must hold
+ * the ptm_res as the first element.
+ * ptm_res corresponds to the error code of a command executed by the TPM.
+ */
+
+typedef uint32_t ptm_res;
+
+/* PTM_GET_TPMESTABLISHED: get the establishment bit */
+struct ptm_est {
+    union {
+        struct {
+            ptm_res tpm_result;
+            unsigned char bit; /* TPM established bit */
+        } resp; /* response */
+    } u;
+};
+
+/* PTM_RESET_TPMESTABLISHED: reset establishment bit */
+struct ptm_reset_est {
+    union {
+        struct {
+            uint8_t loc; /* locality to use */
+        } req; /* request */
+        struct {
+            ptm_res tpm_result;
+        } resp; /* response */
+    } u;
+};
+
+/* PTM_INIT */
+struct ptm_init {
+    union {
+        struct {
+            uint32_t init_flags; /* see definitions below */
+        } req; /* request */
+        struct {
+            ptm_res tpm_result;
+        } resp; /* response */
+    } u;
+};
+
+/* above init_flags */
+#define PTM_INIT_FLAG_DELETE_VOLATILE (1 << 0)
+    /* delete volatile state file after reading it */
+
+/* PTM_SET_LOCALITY */
+struct ptm_loc {
+    union {
+        struct {
+            uint8_t loc; /* locality to set */
+        } req; /* request */
+        struct {
+            ptm_res tpm_result;
+        } resp; /* response */
+    } u;
+};
+
+/* PTM_HASH_DATA: hash given data */
+struct ptm_hdata {
+    union {
+        struct {
+            uint32_t length;
+            uint8_t data[4096];
+        } req; /* request */
+        struct {
+            ptm_res tpm_result;
+        } resp; /* response */
+    } u;
+};
+
+/*
+ * size of the TPM state blob to transfer; x86_64 can handle 8k,
+ * ppc64le only ~7k; keep the response below a 4k page size
+ */
+#define PTM_STATE_BLOB_SIZE (3 * 1024)
+
+/*
+ * The following is the data structure to get state blobs from the TPM.
+ * If the size of the state blob exceeds the PTM_STATE_BLOB_SIZE, multiple reads
+ * with this ioctl and with adjusted offset are necessary. All bytes
+ * must be transferred and the transfer is done once the last byte has been
+ * returned.
+ * It is possible to use the read() interface for reading the data; however,
+ * the first bytes of the state blob will be part of the response to the ioctl();
+ * a subsequent read() is only necessary if the total length (totlength) exceeds
+ * the number of received bytes. seek() is not supported.
+ */
+struct ptm_getstate {
+    union {
+        struct {
+            uint32_t state_flags; /* may be: PTM_STATE_FLAG_DECRYPTED */
+            uint32_t type;        /* which blob to pull */
+            uint32_t offset;      /* offset from where to read */
+        } req; /* request */
+        struct {
+            ptm_res tpm_result;
+            uint32_t state_flags; /* may be: PTM_STATE_FLAG_ENCRYPTED */
+            uint32_t totlength;   /* total length that will be transferred */
+            uint32_t length;      /* number of bytes in following buffer */
+            uint8_t  data[PTM_STATE_BLOB_SIZE];
+        } resp; /* response */
+    } u;
+};
+
+/* TPM state blob types */
+#define PTM_BLOB_TYPE_PERMANENT  1
+#define PTM_BLOB_TYPE_VOLATILE   2
+#define PTM_BLOB_TYPE_SAVESTATE  3
+
+/* state_flags above : */
+#define PTM_STATE_FLAG_DECRYPTED     1 /* on input:  get decrypted state */
+#define PTM_STATE_FLAG_ENCRYPTED     2 /* on output: state is encrypted */
+
+/*
+ * The following is the data structure to set state blobs in the TPM.
+ * If the size of the state blob exceeds the PTM_STATE_BLOB_SIZE, multiple
+ * 'writes' using this ioctl are necessary. The last packet is indicated
+ * by the length being smaller than the PTM_STATE_BLOB_SIZE.
+ * The very first packet may have a length indicator of '0' enabling
+ * a write() with all the bytes from a buffer. If the write() interface
+ * is used, a final ioctl with a non-full buffer must be made to indicate
+ * that all data were transferred (a write with 0 bytes would not work).
+ */
+struct ptm_setstate {
+    union {
+        struct {
+            uint32_t state_flags; /* may be PTM_STATE_FLAG_ENCRYPTED */
+            uint32_t type;        /* which blob to set */
+            uint32_t length;      /* length of the data;
+                                     use 0 on the first packet to
+                                     transfer using write() */
+            uint8_t data[PTM_STATE_BLOB_SIZE];
+        } req; /* request */
+        struct {
+            ptm_res tpm_result;
+        } resp; /* response */
+    } u;
+};
+
+/*
+ * PTM_GET_CONFIG: Data structure to get runtime configuration information
+ * such as which keys are applied.
+ */
+struct ptm_getconfig {
+    union {
+        struct {
+            ptm_res tpm_result;
+            uint32_t flags;
+        } resp; /* response */
+    } u;
+};
+
+#define PTM_CONFIG_FLAG_FILE_KEY        0x1
+#define PTM_CONFIG_FLAG_MIGRATION_KEY   0x2
+
+
+typedef uint64_t ptm_cap;
+typedef struct ptm_est ptm_est;
+typedef struct ptm_reset_est ptm_reset_est;
+typedef struct ptm_loc ptm_loc;
+typedef struct ptm_hdata ptm_hdata;
+typedef struct ptm_init ptm_init;
+typedef struct ptm_getstate ptm_getstate;
+typedef struct ptm_setstate ptm_setstate;
+typedef struct ptm_getconfig ptm_getconfig;
+
+/* capability flags returned by PTM_GET_CAPABILITY */
+#define PTM_CAP_INIT               (1)
+#define PTM_CAP_SHUTDOWN           (1<<1)
+#define PTM_CAP_GET_TPMESTABLISHED (1<<2)
+#define PTM_CAP_SET_LOCALITY       (1<<3)
+#define PTM_CAP_HASHING            (1<<4)
+#define PTM_CAP_CANCEL_TPM_CMD     (1<<5)
+#define PTM_CAP_STORE_VOLATILE     (1<<6)
+#define PTM_CAP_RESET_TPMESTABLISHED (1<<7)
+#define PTM_CAP_GET_STATEBLOB      (1<<8)
+#define PTM_CAP_SET_STATEBLOB      (1<<9)
+#define PTM_CAP_STOP               (1<<10)
+#define PTM_CAP_GET_CONFIG         (1<<11)
+
+enum {
+    PTM_GET_CAPABILITY     = _IOR('P', 0, ptm_cap),
+    PTM_INIT               = _IOWR('P', 1, ptm_init),
+    PTM_SHUTDOWN           = _IOR('P', 2, ptm_res),
+    PTM_GET_TPMESTABLISHED = _IOR('P', 3, ptm_est),
+    PTM_SET_LOCALITY       = _IOWR('P', 4, ptm_loc),
+    PTM_HASH_START         = _IOR('P', 5, ptm_res),
+    PTM_HASH_DATA          = _IOWR('P', 6, ptm_hdata),
+    PTM_HASH_END           = _IOR('P', 7, ptm_res),
+    PTM_CANCEL_TPM_CMD     = _IOR('P', 8, ptm_res),
+    PTM_STORE_VOLATILE     = _IOR('P', 9, ptm_res),
+    PTM_RESET_TPMESTABLISHED = _IOWR('P', 10, ptm_reset_est),
+    PTM_GET_STATEBLOB      = _IOWR('P', 11, ptm_getstate),
+    PTM_SET_STATEBLOB      = _IOWR('P', 12, ptm_setstate),
+    PTM_STOP               = _IOR('P', 13, ptm_res),
+    PTM_GET_CONFIG         = _IOR('P', 14, ptm_getconfig),
+};
+
+#endif /* _TPM_IOCTL_H */
diff --git a/hw/tpm/tpm_passthrough.c b/hw/tpm/tpm_passthrough.c
index e88c0d20bc..050f2ba850 100644
--- a/hw/tpm/tpm_passthrough.c
+++ b/hw/tpm/tpm_passthrough.c
@@ -33,6 +33,7 @@
 #include "sysemu/tpm_backend_int.h"
 #include "tpm_tis.h"
 #include "tpm_util.h"
+#include "tpm_ioctl.h"
 
 #define DEBUG_TPM 0
 
@@ -45,6 +46,7 @@
 #define TYPE_TPM_PASSTHROUGH "tpm-passthrough"
 #define TPM_PASSTHROUGH(obj) \
     OBJECT_CHECK(TPMPassthruState, (obj), TYPE_TPM_PASSTHROUGH)
+#define TYPE_TPM_CUSE "tpm-cuse"
 
 static const TPMDriverOps tpm_passthrough_driver;
 
@@ -71,12 +73,18 @@ struct TPMPassthruState {
     bool had_startup_error;
 
     TPMVersion tpm_version;
+    ptm_cap cuse_cap; /* capabilities of the CUSE TPM */
+    uint8_t cur_locty_number; /* last set locality */
 };
 
 typedef struct TPMPassthruState TPMPassthruState;
 
 #define TPM_PASSTHROUGH_DEFAULT_DEVICE "/dev/tpm0"
 
+#define TPM_PASSTHROUGH_USES_CUSE_TPM(tpm_pt) (tpm_pt->cuse_cap != 0)
+
+#define TPM_CUSE_IMPLEMENTS_ALL(S, cap) (((S)->cuse_cap & (cap)) == (cap))
+
 /* functions */
 
 static void tpm_passthrough_cancel_cmd(TPMBackend *tb);
@@ -148,7 +156,28 @@ static bool tpm_passthrough_is_selftest(const uint8_t *in, uint32_t in_len)
     return false;
 }
 
+static int tpm_passthrough_set_locality(TPMPassthruState *tpm_pt,
+                                        uint8_t locty_number)
+{
+    ptm_loc loc;
+
+    if (TPM_PASSTHROUGH_USES_CUSE_TPM(tpm_pt)) {
+        if (tpm_pt->cur_locty_number != locty_number) {
+            loc.u.req.loc = locty_number;
+            if (ioctl(tpm_pt->tpm_fd, PTM_SET_LOCALITY, &loc) < 0) {
+                error_report("tpm_cuse: could not set locality on "
+                             "CUSE TPM: %s",
+                             strerror(errno));
+                return -1;
+            }
+            tpm_pt->cur_locty_number = locty_number;
+        }
+    }
+    return 0;
+}
+
 static int tpm_passthrough_unix_tx_bufs(TPMPassthruState *tpm_pt,
+                                        uint8_t locality_number,
                                         const uint8_t *in, uint32_t in_len,
                                         uint8_t *out, uint32_t out_len,
                                         bool *selftest_done)
@@ -157,6 +186,11 @@ static int tpm_passthrough_unix_tx_bufs(TPMPassthruState *tpm_pt,
     bool is_selftest;
     const struct tpm_resp_hdr *hdr;
 
+    ret = tpm_passthrough_set_locality(tpm_pt, locality_number);
+    if (ret < 0) {
+        goto err_exit;
+    }
+
     tpm_pt->tpm_op_canceled = false;
     tpm_pt->tpm_executing = true;
     *selftest_done = false;
@@ -207,10 +241,12 @@ err_exit:
 }
 
 static int tpm_passthrough_unix_transfer(TPMPassthruState *tpm_pt,
+                                         uint8_t locality_number,
                                          const TPMLocality *locty_data,
                                          bool *selftest_done)
 {
     return tpm_passthrough_unix_tx_bufs(tpm_pt,
+                                        locality_number,
                                         locty_data->w_buffer.buffer,
                                         locty_data->w_offset,
                                         locty_data->r_buffer.buffer,
@@ -231,6 +267,7 @@ static void tpm_passthrough_worker_thread(gpointer data,
     switch (cmd) {
     case TPM_BACKEND_CMD_PROCESS_CMD:
         tpm_passthrough_unix_transfer(tpm_pt,
+                                      thr_parms->tpm_state->locty_number,
                                       thr_parms->tpm_state->locty_data,
                                       &selftest_done);
 
@@ -247,6 +284,93 @@ static void tpm_passthrough_worker_thread(gpointer data,
 }
 
 /*
+ * Gracefully shut down the external CUSE TPM
+ */
+static void tpm_passthrough_shutdown(TPMPassthruState *tpm_pt)
+{
+    ptm_res res;
+
+    if (TPM_PASSTHROUGH_USES_CUSE_TPM(tpm_pt)) {
+        if (ioctl(tpm_pt->tpm_fd, PTM_SHUTDOWN, &res) < 0) {
+            error_report("tpm_cuse: Could not cleanly shut down "
+                         "the CUSE TPM: %s",
+                         strerror(errno));
+        }
+    }
+}
+
+/*
+ * Probe for the CUSE TPM by sending an ioctl() requesting its
+ * capability flags.
+ */
+static int tpm_passthrough_cuse_probe(TPMPassthruState *tpm_pt)
+{
+    int rc = 0;
+
+    if (ioctl(tpm_pt->tpm_fd, PTM_GET_CAPABILITY, &tpm_pt->cuse_cap) < 0) {
+        error_report("Error: CUSE TPM was requested, but probing failed");
+        rc = -1;
+    }
+
+    return rc;
+}
+
+static int tpm_passthrough_cuse_check_caps(TPMPassthruState *tpm_pt)
+{
+    int rc = 0;
+    ptm_cap caps = 0;
+    const char *tpm = NULL;
+
+    /* check for min. required capabilities */
+    switch (tpm_pt->tpm_version) {
+    case TPM_VERSION_1_2:
+        caps = PTM_CAP_INIT | PTM_CAP_SHUTDOWN | PTM_CAP_GET_TPMESTABLISHED |
+               PTM_CAP_SET_LOCALITY;
+        tpm = "1.2";
+        break;
+    case TPM_VERSION_2_0:
+        caps = PTM_CAP_INIT | PTM_CAP_SHUTDOWN | PTM_CAP_GET_TPMESTABLISHED |
+               PTM_CAP_SET_LOCALITY | PTM_CAP_RESET_TPMESTABLISHED;
+        tpm = "2";
+        break;
+    case TPM_VERSION_UNSPEC:
+        error_report("tpm_cuse: %s: TPM version has not been set",
+                     __func__);
+        return -1;
+    }
+
+    if (!TPM_CUSE_IMPLEMENTS_ALL(tpm_pt, caps)) {
+        error_report("tpm_cuse: TPM does not implement minimum set of required "
+                     "capabilities for TPM %s (0x%x)", tpm, (int)caps);
+        rc = -1;
+    }
+
+    return rc;
+}
+
+/*
+ * Initialize the external CUSE TPM
+ */
+static int tpm_passthrough_cuse_init(TPMPassthruState *tpm_pt)
+{
+    int rc = 0;
+    ptm_init init = {
+        .u.req.init_flags = PTM_INIT_FLAG_DELETE_VOLATILE,
+    };
+
+    if (TPM_PASSTHROUGH_USES_CUSE_TPM(tpm_pt)) {
+        if (ioctl(tpm_pt->tpm_fd, PTM_INIT, &init) < 0) {
+            error_report("tpm_cuse: Detected CUSE TPM but could not "
+                         "send INIT: %s",
+                         strerror(errno));
+            rc = -1;
+        }
+    }
+
+    return rc;
+}
+
+/*
  * Start the TPM (thread). If it had been started before, then terminate
  * and start it again.
  */
@@ -261,6 +385,8 @@ static int tpm_passthrough_startup_tpm(TPMBackend *tb)
                               tpm_passthrough_worker_thread,
                               &tpm_pt->tpm_thread_params);
 
+    tpm_passthrough_cuse_init(tpm_pt);
+
     return 0;
 }
 
@@ -291,14 +417,43 @@ static int tpm_passthrough_init(TPMBackend *tb, TPMState *s,
 
 static bool tpm_passthrough_get_tpm_established_flag(TPMBackend *tb)
 {
+    TPMPassthruState *tpm_pt = TPM_PASSTHROUGH(tb);
+    ptm_est est;
+
+    if (TPM_PASSTHROUGH_USES_CUSE_TPM(tpm_pt)) {
+        if (ioctl(tpm_pt->tpm_fd, PTM_GET_TPMESTABLISHED, &est) < 0) {
+            error_report("tpm_cuse: Could not get the TPM established "
+                         "flag from the CUSE TPM: %s",
+                         strerror(errno));
+            return false;
+        }
+        return (est.u.resp.bit != 0);
+    }
     return false;
 }
 
 static int tpm_passthrough_reset_tpm_established_flag(TPMBackend *tb,
                                                       uint8_t locty)
 {
+    TPMPassthruState *tpm_pt = TPM_PASSTHROUGH(tb);
+    int rc = 0;
+    ptm_reset_est ptmreset_est;
+
     /* only a TPM 2.0 will support this */
-    return 0;
+    if (tpm_pt->tpm_version == TPM_VERSION_2_0) {
+        if (TPM_PASSTHROUGH_USES_CUSE_TPM(tpm_pt)) {
+            ptmreset_est.u.req.loc = tpm_pt->cur_locty_number;
+
+            if (ioctl(tpm_pt->tpm_fd, PTM_RESET_TPMESTABLISHED,
+                      &ptmreset_est) < 0) {
+                error_report("tpm_cuse: Could not reset the establishment bit "
+                             "failed: %s",
+                             strerror(errno));
+                rc = -1;
+            }
+        }
+    }
+    return rc;
 }
 
 static bool tpm_passthrough_get_startup_error(TPMBackend *tb)
@@ -329,7 +484,8 @@ static void tpm_passthrough_deliver_request(TPMBackend *tb)
 static void tpm_passthrough_cancel_cmd(TPMBackend *tb)
 {
     TPMPassthruState *tpm_pt = TPM_PASSTHROUGH(tb);
-    int n;
+    ptm_res res;
+    static bool error_printed;
 
     /*
      * As of Linux 3.7 the tpm_tis driver does not properly cancel
@@ -338,17 +494,34 @@ static void tpm_passthrough_cancel_cmd(TPMBackend *tb)
      * command, e.g., a command executed on the host.
      */
     if (tpm_pt->tpm_executing) {
-        if (tpm_pt->cancel_fd >= 0) {
-            n = write(tpm_pt->cancel_fd, "-", 1);
-            if (n != 1) {
-                error_report("Canceling TPM command failed: %s",
-                             strerror(errno));
-            } else {
-                tpm_pt->tpm_op_canceled = true;
+        if (TPM_PASSTHROUGH_USES_CUSE_TPM(tpm_pt)) {
+            if (TPM_CUSE_IMPLEMENTS_ALL(tpm_pt, PTM_CAP_CANCEL_TPM_CMD)) {
+                if (ioctl(tpm_pt->tpm_fd, PTM_CANCEL_TPM_CMD, &res) < 0) {
+                    error_report("tpm_cuse: Could not cancel command on "
+                                 "CUSE TPM: %s",
+                                 strerror(errno));
+                } else if (res != TPM_SUCCESS) {
+                    if (!error_printed) {
+                        error_report("TPM error code from command "
+                                     "cancellation of CUSE TPM: 0x%x", res);
+                        error_printed = true;
+                    }
+                } else {
+                    tpm_pt->tpm_op_canceled = true;
+                }
             }
         } else {
-            error_report("Cannot cancel TPM command due to missing "
-                         "TPM sysfs cancel entry");
+            if (tpm_pt->cancel_fd >= 0) {
+                if (write(tpm_pt->cancel_fd, "-", 1) != 1) {
+                    error_report("Canceling TPM command failed: %s",
+                                 strerror(errno));
+                } else {
+                    tpm_pt->tpm_op_canceled = true;
+                }
+            } else {
+                error_report("Cannot cancel TPM command due to missing "
+                             "TPM sysfs cancel entry");
+            }
         }
     }
 }
@@ -378,6 +551,11 @@ static int tpm_passthrough_open_sysfs_cancel(TPMBackend *tb)
     char *dev;
     char path[PATH_MAX];
 
+    if (TPM_PASSTHROUGH_USES_CUSE_TPM(tpm_pt)) {
+        /* not needed, but so we have a fd */
+        return qemu_open("/dev/null", O_WRONLY);
+    }
+
     if (tb->cancel_path) {
         fd = qemu_open(tb->cancel_path, O_WRONLY);
         if (fd < 0) {
@@ -412,12 +590,22 @@ static int tpm_passthrough_handle_device_opts(QemuOpts *opts, TPMBackend *tb)
 {
     TPMPassthruState *tpm_pt = TPM_PASSTHROUGH(tb);
     const char *value;
+    bool have_cuse = false;
+
+    value = qemu_opt_get(opts, "type");
+    if (value != NULL && !strcmp("cuse-tpm", value)) {
+        have_cuse = true;
+    }
 
     value = qemu_opt_get(opts, "cancel-path");
     tb->cancel_path = g_strdup(value);
 
     value = qemu_opt_get(opts, "path");
     if (!value) {
+        if (have_cuse) {
+            error_report("Missing path to access CUSE TPM");
+            goto err_free_parameters;
+        }
         value = TPM_PASSTHROUGH_DEFAULT_DEVICE;
     }
 
@@ -432,15 +620,36 @@ static int tpm_passthrough_handle_device_opts(QemuOpts *opts, TPMBackend *tb)
         goto err_free_parameters;
     }
 
+    tpm_pt->cur_locty_number = ~0;
+
+    if (have_cuse) {
+        if (tpm_passthrough_cuse_probe(tpm_pt)) {
+            goto err_close_tpmdev;
+        }
+        /* init TPM for probing */
+        if (tpm_passthrough_cuse_init(tpm_pt)) {
+            goto err_close_tpmdev;
+        }
+    }
+
     if (tpm_util_test_tpmdev(tpm_pt->tpm_fd, &tpm_pt->tpm_version)) {
         error_report("'%s' is not a TPM device.",
                      tpm_pt->tpm_dev);
         goto err_close_tpmdev;
     }
 
+    if (have_cuse) {
+        if (tpm_passthrough_cuse_check_caps(tpm_pt)) {
+            goto err_close_tpmdev;
+        }
+    }
+
+
     return 0;
 
  err_close_tpmdev:
+    tpm_passthrough_shutdown(tpm_pt);
+
     qemu_close(tpm_pt->tpm_fd);
     tpm_pt->tpm_fd = -1;
 
@@ -491,6 +700,8 @@ static void tpm_passthrough_destroy(TPMBackend *tb)
 
     tpm_backend_thread_end(&tpm_pt->tbt);
 
+    tpm_passthrough_shutdown(tpm_pt);
+
     qemu_close(tpm_pt->tpm_fd);
     qemu_close(tpm_pt->cancel_fd);
 
@@ -564,3 +775,44 @@ static void tpm_passthrough_register(void)
 }
 
 type_init(tpm_passthrough_register)
+
+/* CUSE TPM */
+static const char *tpm_passthrough_cuse_create_desc(void)
+{
+    return "CUSE TPM backend driver";
+}
+
+static const TPMDriverOps tpm_cuse_driver = {
+    .type                     = TPM_TYPE_CUSE_TPM,
+    .opts                     = tpm_passthrough_cmdline_opts,
+    .desc                     = tpm_passthrough_cuse_create_desc,
+    .create                   = tpm_passthrough_create,
+    .destroy                  = tpm_passthrough_destroy,
+    .init                     = tpm_passthrough_init,
+    .startup_tpm              = tpm_passthrough_startup_tpm,
+    .realloc_buffer           = tpm_passthrough_realloc_buffer,
+    .reset                    = tpm_passthrough_reset,
+    .had_startup_error        = tpm_passthrough_get_startup_error,
+    .deliver_request          = tpm_passthrough_deliver_request,
+    .cancel_cmd               = tpm_passthrough_cancel_cmd,
+    .get_tpm_established_flag = tpm_passthrough_get_tpm_established_flag,
+    .reset_tpm_established_flag = tpm_passthrough_reset_tpm_established_flag,
+    .get_tpm_version          = tpm_passthrough_get_tpm_version,
+};
+
+static const TypeInfo tpm_cuse_info = {
+    .name = TYPE_TPM_CUSE,
+    .parent = TYPE_TPM_BACKEND,
+    .instance_size = sizeof(TPMPassthruState),
+    .class_init = tpm_passthrough_class_init,
+    .instance_init = tpm_passthrough_inst_init,
+    .instance_finalize = tpm_passthrough_inst_finalize,
+};
+
+static void tpm_cuse_register(void)
+{
+    type_register_static(&tpm_cuse_info);
+    tpm_register_driver(&tpm_cuse_driver);
+}
+
+type_init(tpm_cuse_register)
diff --git a/qapi-schema.json b/qapi-schema.json
index 5658723b37..53120d0f63 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -3522,10 +3522,12 @@
 # An enumeration of TPM types
 #
 # @passthrough: TPM passthrough type
+# @cuse-tpm: CUSE TPM type
+#            Since: 2.6
 #
 # Since: 1.5
 ##
-{ 'enum': 'TpmType', 'data': [ 'passthrough' ] }
+{ 'enum': 'TpmType', 'data': [ 'passthrough', 'cuse-tpm' ] }
 
 ##
 # @query-tpm-types:
@@ -3554,6 +3556,17 @@
                                              '*cancel-path' : 'str'} }
 
 ##
+# @TPMCuseOptions:
+#
+# Information about the CUSE TPM type
+#
+# @path: string describing the path used for accessing the TPM device
+#
+# Since: 2.6
+##
+{ 'struct': 'TPMCuseOptions', 'data': { 'path' : 'str'}}
+
+##
 # @TpmTypeOptions:
 #
 # A union referencing different TPM backend types' configuration options
@@ -3563,7 +3576,8 @@
 # Since: 1.5
 ##
 { 'union': 'TpmTypeOptions',
-   'data': { 'passthrough' : 'TPMPassthroughOptions' } }
+   'data': { 'passthrough' : 'TPMPassthroughOptions',
+             'cuse-tpm' : 'TPMCuseOptions' } }
 
 ##
 # @TpmInfo:
diff --git a/qemu-options.hx b/qemu-options.hx
index a71aaf8ea8..e0f1d8e676 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2763,7 +2763,10 @@ DEF("tpmdev", HAS_ARG, QEMU_OPTION_tpmdev, \
     "-tpmdev passthrough,id=id[,path=path][,cancel-path=path]\n"
     "                use path to provide path to a character device; default is /dev/tpm0\n"
     "                use cancel-path to provide path to TPM's cancel sysfs entry; if\n"
-    "                not provided it will be searched for in /sys/class/misc/tpm?/device\n",
+    "                not provided it will be searched for in /sys/class/misc/tpm?/device\n"
+    "-tpmdev cuse-tpm,id=id,path=path\n"
+    "                use path to provide path to a character device to talk to the\n"
+    "                TPM emulator providing a CUSE interface\n",
     QEMU_ARCH_ALL)
 STEXI
 
@@ -2772,8 +2775,8 @@ The general form of a TPM device option is:
 
 @item -tpmdev @var{backend} ,id=@var{id} [,@var{options}]
 @findex -tpmdev
-Backend type must be:
-@option{passthrough}.
+Backend type must be either one of the following:
+@option{passthrough}, @option{cuse-tpm}.
 
 The specific backend type will determine the applicable options.
 The @code{-tpmdev} option creates the TPM backend and requires a
@@ -2823,6 +2826,18 @@ To create a passthrough TPM use the following two options:
 Note that the @code{-tpmdev} id is @code{tpm0} and is referenced by
 @code{tpmdev=tpm0} in the device option.
 
+@item -tpmdev cuse-tpm, id=@var{id}, path=@var{path}
+
+(Linux-host only) Enable access to a TPM emulator with a CUSE interface.
+
+@option{path} specifies the path to the CUSE TPM character device.
+
+To create a backend device accessing the CUSE TPM emulator using /dev/vtpm
+use the following two options:
+@example
+-tpmdev cuse-tpm,id=tpm0,path=/dev/vtpm -device tpm-tis,tpmdev=tpm0
+@end example
+
 @end table
 
 ETEXI
diff --git a/tpm.c b/tpm.c
index 9a7c7114d3..5ec2373286 100644
--- a/tpm.c
+++ b/tpm.c
@@ -25,7 +25,7 @@ static QLIST_HEAD(, TPMBackend) tpm_backends =
 
 
 #define TPM_MAX_MODELS      1
-#define TPM_MAX_DRIVERS     1
+#define TPM_MAX_DRIVERS     2
 
 static TPMDriverOps const *be_drivers[TPM_MAX_DRIVERS] = {
     NULL,
@@ -272,6 +272,15 @@ static TPMInfo *qmp_query_tpm_inst(TPMBackend *drv)
             tpo->has_cancel_path = true;
         }
         break;
+    case TPM_TYPE_CUSE_TPM:
+        res->options->type = TPM_TYPE_OPTIONS_KIND_CUSE_TPM;
+        tpo = g_new0(TPMPassthroughOptions, 1);
+        res->options->u.passthrough.data = tpo;
+        if (drv->path) {
+            tpo->path = g_strdup(drv->path);
+            tpo->has_path = true;
+        }
+        break;
     case TPM_TYPE__MAX:
         break;
     }
-- 
2.11.0