tree e5e26b0aca654d3f346738596668c72dbcfd6f8b
parent 8a2bbeceba8f885c9118be5c26bf0549b38846ac
author Stefan Berger <stefanb@linux.ibm.com> 1660163136 -0400
committer Stefan Berger <stefanb@us.ibm.com> 1662487725 -0400

swtpm: Implement release-lock-outgoing parameter for --migration option

Implement the release-lock-outgoing parameter for the --migration option
that causes the storage lock to be released once the 'savestate' blob
transfer has been initiated. To not release the lock too early users must
first get the 'permanent' and 'volatile' state blobs and the 'savestate'
blob must be transferred as the last blob.

When migrating a VM the migration may fail and execution will then resume
on the originating side. In this fallback case the swtpm on the
destination side may need some time to terminate and release the lock.
Therefore, add a loop to the code attempting to re-lock the storage
directory on the source side for a few times until on the destination
side swtpm has released the lock. Retry the locking for 100 times
with 10ms in between. The retries will only ever be necessary if a TPM
command is immediately executed upon resume [this may be difficult
to test]. The negative side effects of this could be that the loop is not
long enough to grab the lock or that a short-duration TPM command will
time out inside the VM due to the retries delaying when it is processed.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Resolves: https://github.com/stefanberger/swtpm/issues/724