tree 52b4c7076bc65ce35e80901c526c2c70a7869f75
parent 132f51d41b7d3d2b34753fa2a0693c5067438c31
author Stefan Berger <stefanb@linux.ibm.com> 1653921601 -0400
committer Stefan Berger <stefanb@us.ibm.com> 1660830616 -0400

swtpm: Track last command processed by the TPM

Track the last command processed by the TPM so we can determine whether
we may need to send a TPM2_Shutdown() before reset of the TPM 2.

Introduce a variable lastCommand to help track the last command that
was sent to the TPM 2.

In relation to deciding whether a TPM2_Shutdown() needs to be sent, the
tracking of the last-sent command is merely an optimization since for
example a VM with EDK2 will send a TPM2_Shutdown() followed by a
TPM2_GetRandom() upon suspend-to-ram, thus indicating that the last
command was TPM2_GetRandom(). However, under most circumstances it helps
to avoid sending an additional TPM2_Shutdown() if the OS TPM driver sent
one already.

When the suspended VM resume swtpm gets a CMD_INIT that requires swtpm
to decide whether a TPM2_Shutdown() needs to be sent and per the last-sent
command it will then send a TPM2_Shutdown(SU_STATE) as in the abrupt
termination case.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>