Emulated TPM devices and snapshots of running VMs

[Milan Zamazal]

Peter Krempa <pkrempa at redhat.com> writes:

> On Thu, Jul 09, 2020 at 17:54:23 +0200, Milan Zamazal wrote:
>> Peter Krempa <pkrempa at redhat.com> writes:
>> 
>
>> > On Thu, Jul 09, 2020 at 14:14:32 +0200, Milan Zamazal wrote:
>> >> Milan Zamazal <mzamazal at redhat.com> writes:
>> >> 
>> >
>> >> > Hi,
>> >> >
>> >> > I would like to clarify how to make snapshots of running VMs with
>> >> > emulated TPM devices.  As far as I understand QEMU documentation, it's
>> >> > possible to make snapshots of running VMs with TPM, but it's important
>> >> > to retain the state of swtpm.  Does libvirt assist with that in any way
>> >> > or is it completely user's responsibility?  libvirt pauses the VM
>> >> > internally when making a snapshot, which should be the right moment to
>> >> > copy the swtpm data, but the user doesn't have control over it.  Is
>> >> > there a way to make a copy of swtpm data that is guaranteed to be
>> >> > consistent with the snapshot?
>> >> 
>> >> No idea?
>> >
>> > I can comment only on the fact that libvirt doesn't do anything
>> > regarding snapshots on a VM with TPM.
>> 
>> Thank you for the confirmation.
>> 
>> Can anybody confirm there is no way to perform custom actions while a VM
>> is frozen by libvirt when making a memory snapshot, before we start
>> thinking about workarounds and/or filing a RFE?
>
> No, currently we don't support any custom actions at the point when the
> external memory snapshot is finalized prior to continuing the VM.
>
> Please file a generic RFE for snapshoting including TPM rather than a
> partial one where you'll request a way to do your hack.

OK, thanks, done: https://bugzilla.redhat.com/1855367