Re: [PATCH v7 08/10] tpm: Proxy driver for supporting multiple emulated TPMs

From: Stefan Berger
Date: Sat Mar 12 2016 - 20:52:47 EST

On 03/12/2016 01:51 PM, Jarkko Sakkinen wrote:
On Fri, Mar 11, 2016 at 09:51:03PM -0500, Stefan Berger wrote:
This patch implements a proxy 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.
With my test script [1] running on QEMU and TPM 2.0 simulator running on the
host side I get this:

$ python tpm2-simulator-vtpm --host=
80 01 00 00 00 0c 00 00 01 44 00 00
80 01 00 00 00 0a 00 00 00 00
Traceback (most recent call last):
File "tpm2-simulator-vtpm", line 85, in <module>
File "tpm2-simulator-vtpm", line 80, in main
resp = client.send_cmd(stream)
File "/home/tpmdd/tpm2-scripts/", line 454, in send_cmd
rsp = self.simulator.send_cmd(cmd)
File "/home/tpmdd/tpm2-scripts/", line 436, in send_cmd
raise SimulatorError("Empty response")
tpm2.SimulatorError: Empty response

However, the process does not exit before the read call expires:

$ python tpm2-list-handles
Traceback (most recent call last):
File "tpm2-list-handles", line 61, in <module>
File "tpm2-list-handles", line 51, in main
handles += client.get_cap(tpm2.TPM2_CAP_HANDLES, tpm2.HR_LOADED_SESSION)
File "/home/tpmdd/tpm2-scripts/", line 782, in get_cap
next_handles, more_data = self.__get_cap_cnt(cap, pt, 1)
File "/home/tpmdd/tpm2-scripts/", line 766, in __get_cap_cnt
rsp = self.send_cmd(cmd)[10:]
File "/home/tpmdd/tpm2-scripts/", line 458, in send_cmd
rsp =
IOError: [Errno 62] Timer expired

The server side stays stuck unti this happens.

This fix should solve the problem:

diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c b/drivers/char/tpm/tpm_vtpm_proxy.c
index d73944e..01e5070 100644
--- a/drivers/char/tpm/tpm_vtpm_proxy.c
+++ b/drivers/char/tpm/tpm_vtpm_proxy.c
@@ -456,10 +456,10 @@ err_delete_proxy_dev:
static void vtpm_proxy_delete_device(struct proxy_dev *proxy_dev)
- tpm_chip_unregister(proxy_dev->chip);

+ tpm_chip_unregister(proxy_dev->chip);

Can you let me know whether this gets it working for you? I'd prepare a v9.