Re: [PATCH v3 1/3] tpm: vtpm_proxy: Implement new ioctl to get supported flags

[Stefan Berger]

On 05/04/2017 11:34 AM, Jason Gunthorpe wrote:
> On Thu, May 04, 2017 at 10:56:25AM -0400, Stefan Berger wrote:
> > Implement VTPM_PROXY_IOC_GET_SUPT_FLAGS ioctl to get the bitmask
> > of flags that the vtpm_proxy driver supports in the
> > VTPM_PROXY_IOC_NEW_DEV ioctl. This helps user space in deciding
> > which flags to set in that ioctl.
> you might be better off just having a VTPM_PROXY_IO_ENABLE_FEATURE
> .feature = LOCALITY

Do you have an example driver that shows how to do this ? Can user space 
query that feature?

> If that fails then the feature is not supported, no real need for the
> query in that case.
>
> Not sure about Jarkko's point on request/release locality.. Is there a
> scenario where the emulator should fail the request locality?

We could filter localities 5 and higher on the level of the driver 
(patch 2/3) since basically there are only 5 localities (0-4) in any TPM 
interface today. The typical hardware locality 4 would be filtered by 
the emulator per policy passed via command line, but I would allow it on 
the level of this driver. An error message would be returned for any 
command executed in that locality, unless the 'policy' allows it. 
Localities 0-3 should just be selectable. The TPM TIS (in the hardware) 
implements some complicated scheme when it comes to allowing the 
selection of a locality and I would say we need none of that but just 
tell the vTPM proxy driver the locality (patch 2/3) in which the next 
command will be executed.


> Jason