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

- From: Stefan Berger \<hidden\>
- Date: 2016-03-10 02:35:15 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2016/03/4706113
- Thread: https://ratatoskr.run/linux-api/2016/03/4705635/t.md

```text
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.

   Stefan
>
> --Andy
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```