# Secure live migration with QEMU-native TLS

## Context

The encryption offered by nova’s `libvirt.live_migration_tunnelled` does not secure all the different migration streams of a nova instance, namely: guest RAM, device state, and disks (via NBD) when using non-shared storage. Further, the “tunnelling via libvirtd” has inherent limitations: (a) it cannot handle live migration of disks in a non-shared storage setup (a.k.a. “block migration”); and (b) has a huge performance overhead and latency, because it burns more CPU and memory bandwidth due to increased number of data copies on both source and destination hosts.

To solve this existing limitation, QEMU and libvirt have gained (refer below for version details) support for “native TLS”, i.e. TLS built into QEMU. This will secure all data transports, including disks that are not on shared storage, without incurring the limitations of the “tunnelled via libvirtd” transport.

To take advantage of the “native TLS” support in QEMU and libvirt, nova has introduced new configuration attribute `libvirt.live_migration_with_native_tls`.

## Prerequisites

1. Version requirement: This feature needs at least libvirt 4.4.0 and QEMU 2.11.

2. A pre-configured TLS environment—i.e. CA, server, and client certificates, their file permissions, et al—must be “correctly” configured (typically by an installer tool) on all relevant compute nodes. To simplify your PKI (Public Key Infrastructure) setup, use deployment tools that take care of handling all the certificate lifecycle management. For example, refer to the “TLS everywhere” guide from the TripleO project.

3. Password-less SSH setup for all relevant compute nodes.

4. On all relevant compute nodes, ensure the TLS-related config attributes in `/etc/libvirt/qemu.conf` are in place:

       default_tls_x509_cert_dir = "/etc/pki/qemu"
       default_tls_x509_verify = 1

   If it is not already configured, modify `/etc/sysconfig/libvirtd` on both (ComputeNode1 & ComputeNode2) to listen for TCP/IP connections:

       LIBVIRTD_ARGS="--listen"

   Then, restart the libvirt daemon (also on both nodes):

       $ systemctl restart libvirtd

   Refer to the “Related information” section on a note about the other TLS-related configuration attributes in `/etc/libvirt/qemu.conf`.

## Validating your TLS environment on compute nodes

Assuming you have two compute hosts (`ComputeNode1`, and `ComputeNode2`) run the virt-pki-validate tool (comes with the `libvirt-client` package on your Linux distribution) on both the nodes to ensure all the necessary PKI files are configured are configured:

    [ComputeNode1]$ virt-pki-validate
    Found /usr/bin/certtool
    Found CA certificate /etc/pki/CA/cacert.pem for TLS Migration Test
    Found client certificate /etc/pki/libvirt/clientcert.pem for ComputeNode1
    Found client private key /etc/pki/libvirt/private/clientkey.pem
    Found server certificate /etc/pki/libvirt/servercert.pem for ComputeNode1
    Found server private key /etc/pki/libvirt/private/serverkey.pem
    Make sure /etc/sysconfig/libvirtd is setup to listen to
    TCP/IP connections and restart the libvirtd service

    [ComputeNode2]$ virt-pki-validate
    Found /usr/bin/certtool
    Found CA certificate /etc/pki/CA/cacert.pem for TLS Migration Test
    Found client certificate /etc/pki/libvirt/clientcert.pem for ComputeNode2
    Found client private key /etc/pki/libvirt/private/clientkey.pem
    Found server certificate /etc/pki/libvirt/servercert.pem for ComputeNode2
    Found server private key /etc/pki/libvirt/private/serverkey.pem
    Make sure /etc/sysconfig/libvirtd is setup to listen to
    TCP/IP connections and restart the libvirtd service

## Other TLS environment related checks on compute nodes

IMPORTANT: Ensure that the permissions of certificate files and keys in `/etc/pki/qemu/*` directory on both source and destination compute nodes to be the following `0640` with `root:qemu` as the group/user. For example, on a Fedora-based system:

    $ ls -lasrtZ /etc/pki/qemu
    total 32
    0 drwxr-xr-x. 10 root root system_u:object_r:cert_t:s0      110 Dec 10 10:39 ..
    4 -rw-r-----.  1 root qemu unconfined_u:object_r:cert_t:s0 1464 Dec 10 11:08 ca-cert.pem
    4 -rw-r-----.  1 root qemu unconfined_u:object_r:cert_t:s0 1558 Dec 10 11:08 server-cert.pem
    4 -rw-r-----.  1 root qemu unconfined_u:object_r:cert_t:s0 1619 Dec 10 11:09 client-cert.pem
    8 -rw-r-----.  1 root qemu unconfined_u:object_r:cert_t:s0 8180 Dec 10 11:09 client-key.pem
    8 -rw-r-----.  1 root qemu unconfined_u:object_r:cert_t:s0 8177 Dec 11 05:35 server-key.pem
    0 drwxr-xr-x.  2 root root unconfined_u:object_r:cert_t:s0  146 Dec 11 06:01 .

## Performing the migration

1. On all relevant compute nodes, enable the `libvirt.live_migration_with_native_tls` configuration attribute and set the `libvirt.live_migration_scheme` configuration attribute to tls:

       [libvirt]
       live_migration_with_native_tls = true
       live_migration_scheme = tls

   Note

   Setting both `libvirt.live_migration_with_native_tls` and `libvirt.live_migration_tunnelled` at the same time is invalid (and disallowed).

   Note

   Not setting `libvirt.live_migration_scheme` to `tls` will result in libvirt using the unencrypted TCP connection without displaying any error or a warning in the logs.

   And restart the `nova-compute` service:

       $ systemctl restart openstack-nova-compute

2. Now that all TLS-related configuration is in place, migrate guests (with or without shared storage) from `ComputeNode1` to `ComputeNode2`. Refer to the Live-migrate instances document on details about live migration.

## Related information

- If you have the relevant libvirt and QEMU versions (mentioned in the “Prerequisites” section earlier), then using the `libvirt.live_migration_with_native_tls` is strongly recommended over the more limited `libvirt.live_migration_tunnelled` option, which is intended to be deprecated in future.

- There are in total nine TLS-related config options in `/etc/libvirt/qemu.conf`:

      default_tls_x509_cert_dir
      default_tls_x509_verify
      nbd_tls
      nbd_tls_x509_cert_dir
      migrate_tls_x509_cert_dir

      vnc_tls_x509_cert_dir
      spice_tls_x509_cert_dir
      vxhs_tls_x509_cert_dir
      chardev_tls_x509_cert_dir

  If you set both `default_tls_x509_cert_dir` and `default_tls_x509_verify` parameters for all certificates, there is no need to specify any of the other `*_tls*` config options.

  The intention (of libvirt) is that you can just use the `default_tls_x509_*` config attributes so that you don’t need to set any other `*_tls*` parameters, _unless_ you need different certificates for some services. The rationale for that is that some services (e.g. migration / NBD) are only exposed to internal infrastructure; while some services (VNC, Spice) might be exposed publicly, so might need different certificates. For OpenStack this does not matter, though, we will stick with the defaults.

- If they are not already open, ensure you open up these TCP ports on your firewall: `16514` (where the authenticated and encrypted TCP/IP socket will be listening on) and `49152-49215` (for regular migration) on all relevant compute nodes. (Otherwise you get `error: internal error: unable to execute QEMU command 'drive-mirror': Failed to connect socket: No route to host`).

this page last updated: 2026-06-10 20:05:07

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