Emulated TPM devices, including TPM data storage, are handled with the external help of swtpm. When a memory snapshot is created, TPM state and data must be stored as well, to ensure consistency when a VM containing an emulated TPM device is restored from the snapshot. To my knowledge, libvirt currently doesn't handle TPM when making a memory snapshot and it doesn't provide a mechanism to copy swtpm data manually while ensuring their consistency with the snapshot. In order to be able to use memory snapshots in VMs with emulated TPM devices without risking errors, mismatches or data loss, libvirt support for TPM data in memory snapshots is needed.
*** This bug has been marked as a duplicate of bug 1855367 ***