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List:       tpmdd-devel
Subject:    Re: [tpmdd-devel] QEMU TPM
From:       Stefan Berger <stefanb () linux ! vnet ! ibm ! com>
Date:       2014-05-18 1:21:20
Message-ID: 53780B10.5060208 () linux ! vnet ! ibm ! com
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On 05/16/2014 11:47 AM, Jason Gunthorpe wrote:
> On Fri, May 16, 2014 at 02:39:02PM +0300, Dmitry Kasatkin wrote:
>
>>>>>> /dev/tpm0 is missing
>>>>>>
>>>>>> and cat pcrs gives following instead of PCRs
>>>>>>
>>>>>> cat /sys/devices/pnp0/00:08/pcrs
>>>>>> Killed
> That is strange, pcrs should certainly not be present if tpm0 is absent.
>
> I wonder if the driver partially started and did not clean up on failure
> exit, that is still a known problem area in this code.
>
>
>>>>> for dmesg |grep -i tpm My kernel says...
>>>>>
>>>>> [    1.257467] ima: No TPM chip found, activating TPM-bypass!
>>>>>
>>>>> but PCR output code does not check for "chip" for NULL.
> It shouldn't ever be null - if the pcr sysfs is present then the chip
> must be present too.
>
> But there should be more tpm related messages if you got in a state with
> pcrs and no dev/tpm!
>
>> Really something got broken.
>> Last kernel version where QEMU TPM works is 3.13-rc7...
>> Neither 3.14.0 nor 3.15-rc5 works...
>>
>> There is set of patches by Jason (in CC) starting from this that changes a lot:
>>
>> afdba32e2a9ea729a9f9f280dbf6c718773c7ded
>>
>> May be he can help?
> Are there more debug messages? Anything from tpm_tis?
>
> This is quemu? Do you have some very simple directions I could follow
> to reproduce it on Ubuntu Trusty?

The problem comes from the call to tpm_add_ppi() failing. There are 
probably many machines out there that don't have the physical presence 
interface and they will fail because of this call failing. So this call 
should not be a reason to fail init. Just ignore the return value and 
handle the tpm_remove_ppi gracefully if previous tpm_add_ppi didn't init 
the variable...

   Stefan


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