Re: [PATCH v2 1/2] tpm2: add session handle context saving and restoring to the space code

[Ken Goldman <kgoldman-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

On 1/31/2017 5:55 PM, James Bottomley wrote:
>
> I can do that, but I think this should be higher than debug.  If this
> trips, something an application was doing will fail with a non TPM
> error and someone may wish to investigate why.  Having a kernel message
> would help with that (but they won't see it if it's debug).
>
> I'm also leaning towards the idea that we should actually have one more
> _tbl slot than we know the TPM does, so that if someone goes over it's
> the TPM that gives them a real TPM out of memory error rather than the
> space code returning -ENOMEM.

I endorse this as a general principle.

1 - When a TPM application does something wrong, the developer will be 
looking for a specific TPM error, not a kernel read() error.

Reserve the kernel errors for when something goes wrong in the device 
driver, not in the application.

2 - As much as possible, the RM should be transparent to the 
application.  The RM should report a failure the same way the SW TPM 
would fail.




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