Questions about the usage of the vTPM implemented in Xen 4.3

[Jordi Cucurull Juan <jordi.cucurull@scytl.com>]

Dear all,

I have recently configured a Xen 4.3 server with the vTPM enabled and a
guest virtual machine that takes advantage of it. After playing a bit
with it, I have a few questions:

1.According to the documentation, to shutdown the vTPM stubdom it is
only needed to normally shutdown the guest VM. Theoretically, the vTPM
stubdom automatically shuts down after this. Nevertheless, if I shutdown
the guest the vTPM stubdom continues active and, moreover, I can start
the machine again and the values of the vTPM are the last ones there
were in the previous instance of the guest. Is this normal?

2.In the documentation it is recommended to avoid accessing the physical
TPM from Dom0 at the same time than the vTPM Manager stubdom.
Nevertheless, I currently have the IMA and the Trousers enabled in Dom0
without any apparent issue. Why is not recommended directly accessing
the physical TPM of Dom0?

3.If it is not recommended to directly accessing the physical TPM in
Dom0, which is the advisable way to check the integrity of this domain?
With solutions such as TBOOT and IntelTXT?

Best regards,
Jordi.