# Re: \[PATCH v6 08/11\] tpm: Driver for supporting multiple emulated TPMs

- From: Stefan Berger \<hidden\>
- Date: 2016-03-10 17:38:31 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2016/03/4706626
- Thread: https://ratatoskr.run/linux-api/2016/03/4705635/t.md

```text
On 03/09/2016 09:57 PM, Andy Lutomirski wrote:
> On Wed, Mar 9, 2016 at 6:34 PM, Stefan Berger
> [ref] wrote:
>> On 03/09/2016 01:01 PM, Andy Lutomirski wrote:
>>> On Wed, Mar 9, 2016 at 9:39 AM, Stefan Berger
>>> [ref] wrote:
>>>> This patch implements a driver for supporting multiple emulated TPMs in a
>>>> system.
>>>>
>>>> The driver implements a device /dev/vtpmx that is used to created
>>>> a client device pair /dev/tpmX (e.g., /dev/tpm10) and a server side that
>>>> is accessed using a file descriptor returned by an ioctl.
>>>> The device /dev/tpmX is the usual TPM device created by the core TPM
>>>> driver. Applications or kernel subsystems can send TPM commands to it
>>>> and the corresponding server-side file descriptor receives these
>>>> commands and delivers them to an emulated TPM.
>>> Nifty!
>>>
>>> Is anyone considering writing a modification or replacement of
>>> trousers that creates claims the real tpm and exposes a vtpm that
>>> handles multiplexing internally?  Does the vtpm driver intelligently
>>> support multiple simultaneous clients?
>>
>> The vtpm driver allows to use an independent trousers instance in each
>> container.
>>
>> Using the VTPM_NEW_DEV ioctl the container mgmt. stack can create a
>> /dev/tpmX (X=0,1,2,...) device and a file descriptor. The file descriptor is
>> passed to a vTPM instance, the /dev/tpmX is moved into the container,
>> meaning a device with the same major/minor numbers is created in the
>> container. This then allows each container to talk to an independent vTPM.
>> The vTPM can either be 1.2 or 2.
> What I meant was:
>
> If two clients connect to the same vTPM slave node, can the master
> program tell requests from the two clients apart?  If so, great!  If
> not, then I'd consider that to be somewhat sad.

vTPM slave node being /dev/tpmX? TPM types of devices can currently only be opened by one application. This can for example be TSS/trousers, which then offers an API to applications for sending TPM commands. That only one application is allowed is a limitation of the existing driver.

   Stefan
```