[Qemu-devel] [PATCH V12 8/8] Add fd parameter for TPM passthrough driver

[Stefan Berger]

Enable the passing of a file descriptor via fd=<..> to access the host's
TPM device using the TPM passthrough driver.

v12:
 - added documentation part

Signed-off-by: Stefan Berger <address@hidden>

---
 hw/tpm_passthrough.c |   74 +++++++++++++++++++++++++++++++++------------------
 qemu-config.c        |    5 +++
 qemu-options.hx      |    6 +++-
 3 files changed, 58 insertions(+), 27 deletions(-)

Index: qemu-git.pt/qemu-config.c
===================================================================
--- qemu-git.pt.orig/qemu-config.c
+++ qemu-git.pt/qemu-config.c
@@ -523,6 +523,11 @@ static QemuOptsList qemu_tpmdev_opts = {
             .type = QEMU_OPT_STRING,
             .help = "Persistent storage for TPM state",
         },
+        {
+            .name = "fd",
+            .type = QEMU_OPT_STRING,
+            .help = "Filedescriptor for accessing the TPM",
+        },
         { /* end of list */ }
     },
 };
Index: qemu-git.pt/hw/tpm_passthrough.c
===================================================================
--- qemu-git.pt.orig/hw/tpm_passthrough.c
+++ qemu-git.pt/hw/tpm_passthrough.c
@@ -362,32 +362,54 @@ static int tpm_passthrough_handle_device
     char buf[64];
     int n;
 
-    value = qemu_opt_get(opts, "path");
-    if (!value) {
-        value = TPM_PASSTHROUGH_DEFAULT_DEVICE;
-    }
-
-    n = snprintf(tb->s.tpm_pt->tpm_dev, sizeof(tb->s.tpm_pt->tpm_dev),
-                 "%s", value);
-
-    if (n >= sizeof(tb->s.tpm_pt->tpm_dev)) {
-        error_report("TPM device path is too long.\n");
-        goto err_exit;
-    }
-
-    snprintf(buf, sizeof(buf), "path=%s", tb->s.tpm_pt->tpm_dev);
-
-    tb->parameters = g_strdup(buf);
-
-    if (tb->parameters == NULL) {
-        return 1;
-    }
-
-    tb->s.tpm_pt->tpm_fd = open(tb->s.tpm_pt->tpm_dev, O_RDWR);
-    if (tb->s.tpm_pt->tpm_fd < 0) {
-        error_report("Cannot access TPM device using '%s'.\n",
-                     tb->s.tpm_pt->tpm_dev);
-        goto err_exit;
+    value = qemu_opt_get(opts, "fd");
+    if (value) {
+        if (qemu_opt_get(opts, "path")) {
+            error_report("fd= is invalid with path=");
+            return -1;
+        }
+
+        tb->s.tpm_pt->tpm_fd = qemu_parse_fd(value);
+        if (tb->s.tpm_pt->tpm_fd < 0) {
+            error_report("Illegal file descriptor for TPM device.\n");
+            return -1;
+        }
+
+        snprintf(buf, sizeof(buf), "fd=%d", tb->s.tpm_pt->tpm_fd);
+
+        tb->parameters = g_strdup(buf);
+
+        if (tb->parameters == NULL) {
+            goto err_close_tpmdev;
+        }
+    } else {
+        value = qemu_opt_get(opts, "path");
+        if (!value) {
+            value = TPM_PASSTHROUGH_DEFAULT_DEVICE;
+        }
+
+        n = snprintf(tb->s.tpm_pt->tpm_dev, sizeof(tb->s.tpm_pt->tpm_dev),
+                     "%s", value);
+
+        if (n >= sizeof(tb->s.tpm_pt->tpm_dev)) {
+            error_report("TPM device path is too long.\n");
+            goto err_exit;
+        }
+
+        snprintf(buf, sizeof(buf), "path=%s", tb->s.tpm_pt->tpm_dev);
+
+        tb->parameters = g_strdup(buf);
+
+        if (tb->parameters == NULL) {
+            return 1;
+        }
+
+        tb->s.tpm_pt->tpm_fd = open(tb->s.tpm_pt->tpm_dev, O_RDWR);
+        if (tb->s.tpm_pt->tpm_fd < 0) {
+            error_report("Cannot access TPM device using '%s'.\n",
+                         tb->s.tpm_pt->tpm_dev);
+            goto err_exit;
+        }
     }
 
     if (tpm_passthrough_test_tpmdev(tb->s.tpm_pt->tpm_fd)) {
Index: qemu-git.pt/qemu-options.hx
===================================================================
--- qemu-git.pt.orig/qemu-options.hx
+++ qemu-git.pt/qemu-options.hx
@@ -1789,7 +1789,7 @@ Use ? to print all available TPM backend
 qemu -tpmdev ?
 @end example
 
address@hidden -tpmdev passthrough, address@hidden, address@hidden
address@hidden -tpmdev passthrough, address@hidden, address@hidden, 
address@hidden
 
 (Linux-host only) Enable access to the host's TPM using the passthrough
 driver.
@@ -1798,6 +1798,10 @@ driver.
 a Linux host this would be @code{/dev/tpm0}.
 @option{path} is optional and by default @code{/dev/tpm0} is used.
 
address@hidden specifies the file descriptor of the host's TPM device.
address@hidden and @option{path} are mutually exclusive.
address@hidden is optional.
+
 Some notes about using the host's TPM with the passthrough driver:
 
 The TPM device accessed by the passthrough driver must not be