Re: [Qemu-devel] [PATCH V19 0/7] Qemu Trusted Platform Module (TPM) integration

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

On 09/27/2012 10:59 AM, Corey Bryant wrote:
>
>
> I reviewed this series and have sent all my comments.  In general the 
> patches look good to me other than the comments I've already made.

Thanks for the review.

>
> The external interfaces (command line and monitor commands) look to be 
> in good shape.  In particular -tpmdev can easily be modified to 
> support future backend vTPM implementations, such a software vTPM.  
> And the monitor commands are simple and straight forward (info TPM and 
> query-TPM with no arguments).
>
> I haven't had the chance to run any tests with the patch series, but I 
> plan to soon.  In the mean time I have a couple of general questions:
>
> I understand that the passthrough driver won't support migration. What 
> happens on a migration attempt?  Does it fail gracefully?

QEMU refuses to migrate.

>
> What happens when a 2nd guest attempts to use the passthrough vTPM 
> after the 1st guest is already using it?  Does it also fail gracefully?
>
Yes, if something blocks /dev/tpm0 then an error message is printed. I 
may adjust that error message suggesting that something else is using 
the device.

> Are there any architecture dependencies for this support?
>

There are some specifics for x86: on Linux one has to do 'modprobe 
tpm_tis force=1' to due missing ACPI support in SeaBIOS so far. I have 
patches for SeaBIOS.

I haven't tried the passthrough driver in VMs running on any other 
architectures, but I don't see reasons why it shouldn't work.

     Stefan