Re: [Qemu-devel] [PATCH V27 1/7] Support for TPM command line options

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

On 03/19/2013 10:28 AM, Markus Armbruster wrote:
> Stefan Berger <stefanb@linux.vnet.ibm.com> writes:
>
>>
>> I can write an OS that sends a command to the TPM and then shuts down
>> without waiting for the program to terminate or the even the response
>> from the TPM to come back . In this case we would need to cancel the
>> command on exit()l.
> Aha, now we're getting somewhere.
>
> Are you talking about the following scenario?
>
> * Guest sends TPM command, QEMU passes it through, QEMU thread blocks in
>    write() to TPM.
>
> * Guest powers down, QEMU is configured to terminate on powerdown, calls
>    exit().
>
> * Unless you explicitly cancel the TPM command, $BAD_THINGS can happen.
>
> If yes, please describe at least one instance of $BAD_THINGS for me
> again.

BAD_THINGS = If a TPM command is executing as in the scenario you are 
describing, the thread will still be caught in the write(), thus the 
QEMU process cannot terminate and will be stuck in the thread-join as it 
is implemented now. If there was no thread-join QEMU would probably 
linger around as a zombie for a while.

    Stefan