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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 from swtpm must be stored as well and then provided when the VM is restored from the snapshot. To my knowledge, libvirt currently doesn't handle TPM data in memory snapshots 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 make memory snapshots of VMs containing emulated TPM devices without risking errors, mismatches or data loss, libvirt support for TPM data in snapshots is needed.
Comment 1Jaroslav Suchanek
2020-07-10 09:05:17 UTC
*** Bug 1855364 has been marked as a duplicate of this bug. ***
Comment 6RHEL Program Management
2022-01-09 07:26:57 UTC
After evaluating this issue, there are no plans to address it further or fix it in an upcoming release. Therefore, it is being closed. If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.
The bug issue still exists.
Steps:
Red Hat Virtualization Manager Web Administration
Software Version:4.5.2.1-0.1.el8ev
RHV node:
vdsm-4.50.1.4-1.el8ev.x86_64
libvirt-8.0.0-10.module+el8.7.0+16047+746a126c.x86_64
kernel-4.18.0-416.el8.x86_64
qemu-kvm-6.2.0-18.module+el8.7.0+15999+d24f860e.x86_64
1. Prepare a running VM with TPM device enabled.
2. Left-click the VM and then right-click and select 'Create Snapshot'
3. Keep the default setting in the popup 'Create Snapshot' window, and fill the name into the 'Description', then click 'OK'.
Test result: Failed to create snapshot with checking 'Saving memory'.
"""
Operation Canceled
Error while executing action:
test-tpm:
Cannot create Snapshot. VM has a TPM device attached.
"""
And I have noticed that this bug has been closed automatically, and do you plan to fix it, thanks.
Hi junqin,
I asked Jaroslav and Michal for helping evaluating.
RHV won't use it, CNV might not be interested in memory snapshots yet. And for migration: live-migration is about having the swtpm state on a shared disk and there are some issues with locking the state files.
So no need to fix it currently.
Please just regard the error you encountered as expected. Thank you!
(In reply to yanqzhan from comment #10)
> And for migration: live-migration is about having the swtpm state on a shared
> disk and there are some issues with locking the state files.
Milan, we migrate VMs with TPM while the swtpm state is not placed on a shared disk, no?
(In reply to Arik from comment #11)
> (In reply to yanqzhan from comment #10)
> > And for migration: live-migration is about having the swtpm state on a shared
> > disk and there are some issues with locking the state files.
>
> Milan, we migrate VMs with TPM while the swtpm state is not placed on a
> shared disk, no?
Yes, swtpm data is stored on a local file system and the transfer is handled transparently by libvirt.
Comment 17RHEL Program Management
2023-02-23 07:27:41 UTC
After evaluating this issue, there are no plans to address it further or fix it in an upcoming release. Therefore, it is being closed. If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.