Merge "TPM: bump service version to enable live migration"

doc/source/admin/emulated-tpm.rst

@@ -7,6 +7,11 @@ Emulated Trusted Platform Module (vTPM)
 Starting in the 22.0.0 (Victoria) release, Nova supports adding an emulated
 virtual `Trusted Platform Module`__ (vTPM) to guests.
 
+.. versionadded:: 33.0.0 (2026.1 Gazpacho)
+
+Starting in the 33.0.0 (2026.1 Gazpacho) release, Nova supports live migration
+of guests with emulated vTPM for the ``host`` TPM secret security mode.
+
 .. __: https://en.wikipedia.org/wiki/Trusted_Platform_Module
 
 
@@ -27,6 +32,11 @@ feature:
 * Set the :oslo.config:option:`libvirt.swtpm_enabled` config option to
   ``True``. This will enable support for both TPM version 1.2 and 2.0.
 
+* Optionally set the :oslo.config:option:`libvirt.supported_tpm_secret_security`
+  config option to configure which security modes to enable. The default is all
+  modes enabled: ``user`` and ``host``. See the next section for more details
+  about TPM secret security modes.
+
 With the above requirements satisfied, verify vTPM support by inspecting the
 traits on the compute node's resource provider:
 
@@ -34,8 +44,12 @@ traits on the compute node's resource provider:
 
    $ COMPUTE_UUID=$(openstack resource provider list --name $HOST -f value -c uuid)
    $ openstack resource provider trait list $COMPUTE_UUID | grep SECURITY_TPM
-   | COMPUTE_SECURITY_TPM_1_2 |
+   | COMPUTE_SECURITY_TPM_1_2                        |
-   | COMPUTE_SECURITY_TPM_2_0 |
+   | COMPUTE_SECURITY_TPM_2_0                        |
+   | COMPUTE_SECURITY_TPM_CRB                        |
+   | COMPUTE_SECURITY_TPM_TIS                        |
+   | COMPUTE_SECURITY_TPM_SECRET_SECURITY_USER       |
+   | COMPUTE_SECURITY_TPM_SECRET_SECURITY_HOST       |
 
 .. __: https://docs.openstack.org/api-guide/key-manager/
 .. __: https://docs.openstack.org/barbican/latest/
@@ -43,6 +57,55 @@ traits on the compute node's resource provider:
 .. __: https://github.com/stefanberger/libtpms/
 
 
+Security
+--------
+
+With a hardware TPM, the root of trust is a secret known only to the TPM user.
+In contrast, an emulated TPM comprises a file on disk which the libvirt daemon
+must be able to present to the guest.
+
+At rest, this file is encrypted using a passphrase stored in a key manager
+service as a secret.
+
+Nova supports a few different security modes that will control secret ownership
+and visibility to the libvirt API. The passphrase is retrieved and used by
+libvirt to unlock the emulated TPM data any time the server is booted.
+
+.. list-table::
+   :header-rows: 1
+   :widths: 20 80
+
+   * - Mode
+     - Description
+   * - ``user``
+     - The passphrase in the key manager is associated with the credentials of
+       the owner of the server (the user who initially created it). The libvirt
+       secret is both ``private`` and ``ephemeral``. A server with this
+       security mode cannot be live migrated. This is the default mode.
+       Existing servers that were created before 33.0.0 (2026.1 Gazpacho) will
+       also have this mode.
+   * - ``host``
+     - The passphrase in the key manager is associated with the credentials of
+       the owner of the server (the user who initially created it). The libvirt
+       secret is not ``private`` and not ``ephemeral``, which means it can be
+       retrieved via the libvirt API or ``virsh`` and it exists on disk. A
+       server with this security mode can be live migrated, including by users
+       other than the owner of the server, such as admin, if API policy allows.
+       To transport the TPM secret to the destination host during a live
+       migration, the libvirt secret is sent over RPC.
+
+Although the above ``user`` mechanism uses a libvirt secret__ that is both
+``private`` (can't be displayed via the libvirt API or ``virsh``) and
+``ephemeral`` (exists only in memory, never on disk), it is theoretically
+possible for a sufficiently privileged user to retrieve the secret and/or vTPM
+data from memory.
+
+A full analysis and discussion of security issues related to emulated TPM is
+beyond the scope of this document.
+
+.. __: https://libvirt.org/formatsecret.html#SecretAttributes
+
+
 Configuring a flavor or image
 -----------------------------
 
@@ -65,6 +128,10 @@ model is only supported with version 2.0.
      - ``hw_tpm_model``
      - Specify the TPM model, ``tpm-tis`` (the default) or ``tpm-crb`` (only
        valid with version ``2.0``.
+   * - ``hw:tpm_secret_security``
+     - \-
+     - Specify the TPM secret security mode, ``user`` (the default) or
+       ``host``.
 
 For example, to configure a flavor to use the TPM 2.0 with the CRB model:
 
@@ -81,38 +148,55 @@ Upon successful boot, the server should see a TPM device such as ``/dev/tpm0``
 which can be used in the same manner as a hardware TPM.
 
 
+Legacy servers and live migration
+---------------------------------
+
+A legacy server can be converted to a TPM secret security mode capable of live
+migration via a resize to a flavor that has the ``hw:tpm_secret_security``
+extra spec set to ``host``.
+
+For example:
+
+.. code-block:: console
+
+   $ openstack flavor set $FLAVOR \
+       --property hw:tpm_version=2.0 \
+       --property hw:tpm_model=tpm-crb \
+       --property hw:tpm_secret_security=host
+
+   $ openstack server resize --flavor $FLAVOR $SERVER
+
+   $ openstack server resize confirm $SERVER
+
+
 Limitations
 -----------
 
-* Only server operations performed by the server owner are supported, as the
+* Rebuild, evacuate, shelve, and rescue of servers with vTPMs is not currently
-  user's credentials are required to unlock the virtual device files on the
+  supported.
-  host. Thus the admin may need to decide whether to grant the user additional
-  policy roles; if not, those operations are effectively disabled.
 
-* Live migration, evacuation, shelving and rescuing of servers with vTPMs is
+* Other limitations will depend on the TPM secret security mode of the server.
-  not currently supported.
 
+.. list-table::
+   :header-rows: 1
+   :widths: 20 80
 
-Security
+   * - Mode
---------
+     - Description
-
+   * - ``user``
-With a hardware TPM, the root of trust is a secret known only to the TPM user.
+     - Only server operations performed by the server owner are supported, as
-In contrast, an emulated TPM comprises a file on disk which the libvirt daemon
+       the user's credentials are required to unlock the virtual device files
-must be able to present to the guest. At rest, this file is encrypted using a
+       on the host in this mode. Thus the admin may need to decide whether to
-passphrase stored in a key manager service. The passphrase in the key manager
+       grant the user additional policy roles or key manager service ACLs; if
-is associated with the credentials of the owner of the server (the user who
+       not, those operations are effectively disabled. Live migration is not
-initially created it). The passphrase is retrieved and used by libvirt to
+       supported in this mode.
-unlock the emulated TPM data any time the server is booted.
+   * - ``host``
-
+     - Certain server operations performed by users other than the server
-Although the above mechanism uses a libvirt secret__ that is both ``private``
+       owner are supported. Hard reboot, start from stopped, and live migration
-(can't be displayed via the libvirt API or ``virsh``) and ``ephemeral`` (exists
+       are supported if API policy allows, without need of key manager service
-only in memory, never on disk), it is theoretically possible for a sufficiently
+       ACLs. This is because nova-compute can read the locally stored Libvirt
-privileged user to retrieve the secret and/or vTPM data from memory.
+       secret from the server's compute host in this mode and the server
-
+       owner's credentials are not required.
-A full analysis and discussion of security issues related to emulated TPM is
-beyond the scope of this document.
-
-.. __: https://libvirt.org/formatsecret.html#SecretAttributes
 
 
 References

nova/compute/api.py

@@ -129,7 +129,7 @@ SUPPORT_SHARES = 67
 MIN_COMPUTE_SOUND_MODEL_TRAITS = 69
 MIN_COMPUTE_USB_MODEL_TRAITS = 70
 
-MIN_COMPUTE_VTPM_LIVE_MIGRATION = None
+MIN_COMPUTE_VTPM_LIVE_MIGRATION = 72
 
 # FIXME(danms): Keep a global cache of the cells we find the
 # first time we look. This needs to be refreshed on a timer or
@@ -290,8 +290,7 @@ def reject_legacy_vtpm_live_migration(function):
             with nova_context.target_cell(context, im.cell_mapping) as cctxt:
                 min_ver = objects.service.Service.get_minimum_version(
                         cctxt, 'nova-compute')
-            if (MIN_COMPUTE_VTPM_LIVE_MIGRATION is None or
+            if min_ver < MIN_COMPUTE_VTPM_LIVE_MIGRATION:
-                    min_ver < MIN_COMPUTE_VTPM_LIVE_MIGRATION):
                 raise exception.VTPMOldCompute()
         return function(self, context, instance, *args, **kwargs)
     return inner

nova/objects/service.py

@@ -37,7 +37,7 @@ __all__ = [
 
 
 # NOTE(danms): This is the global service version counter
-SERVICE_VERSION = 71
+SERVICE_VERSION = 72
 
 
 # NOTE(danms): This is our SERVICE_VERSION history. The idea is that any
@@ -252,6 +252,9 @@ SERVICE_VERSION_HISTORY = (
     # Version 71: Compute RPC v6.5:
     # Add 2nd RPC server for compute service
     {'compute_rpc': '6.5'},
+    # Version 72: Compute RPC v6.5:
+    # Add support for vTPM live migration
+    {'compute_rpc': '6.5'},
 )
 
 # This is the version after which we can rely on having a persistent

releasenotes/notes/vtpm-live-migration-4ef9ab54cd6e3a0b.yaml

@@ -0,0 +1,13 @@
+features:
+  - |
+    The libvirt driver now supports live migration of servers with virtual
+    emulated TPM (vTPM) when the ``hw:tpm_secret_security`` flavor extra spec
+    is set to ``host``. Operators must create flavors which set
+    ``hw:tpm_secret_security`` in order to enable servers to select a
+    particular TPM secret security mode. Pre-existing servers can opt-in to the
+    ``host`` TPM secret security mode by resizing to a flavor which has set
+    ``hw:tpm_secret_security`` to ``host``. Operators may choose which TPM
+    security modes they want to support by setting the
+    ``[libvirt]supported_tpm_secret_security`` configuration option on compute
+    hosts. See the documentation for details:
+    https://docs.openstack.org/nova/latest/admin/emulated-tpm.html