Re: [PATCH v10 2/2] tpm: add backend for mssim

[Stefan Berger <stefanb@linux.ibm.com>]

On 5/1/24 12:21, James Bottomley wrote:
> On Tue, 2024-04-30 at 17:12 -0400, Stefan Berger wrote:
>> On 4/30/24 15:08, James Bottomley wrote:
> [...]
>>> +The mssim backend supports snapshotting and migration by not
>>> resetting
>>
>> I don't thing snapshotting is supported because snapshooting would
>> require you to be able to set the state of the vTPM from the snapshot
>> you started. I would remove the claim.
> 
> I thought we established last time that it can definitely do both (and
> I've tested it because you asked me to).  Snapshotting and migration
> are essentially the same thing, with snapshotting being easier because
> it can be done on the same host meaning the same command line
> parameters.  If you migrate to a different host you need the socket to
> point back to the host serving the vTPM.
> 
> To do this easily you simply keep the vTPM running while the VM is
> undergoing snapshot and migration.  If you're thinking of and extended
> down time for the snapshot, then it's up to the vTPM implementation to
> store the state (or simply keep it running for an extended time doing
> nothing).

Which part of the code injects the state into the vTPM so that it 
resumes with the state of the TPM (PCRs, NVRAM indices, keys, sessions 
etc.) from when the snapshot was taken?


> 
> 
>> Rest LGTM.
> 
> Thanks!
> 
> Regards,
> 
> James
>