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From: Stefan Berger <>
To: Jason Gunthorpe <>
Subject: Re: [PATCH v3 1/3] tpm: vtpm_proxy: Implement new ioctl to get supported flags
Date: Thu, 4 May 2017 13:28:17 -0400	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 05/04/2017 01:20 PM, Jason Gunthorpe wrote:
> On Thu, May 04, 2017 at 01:13:18PM -0400, Stefan Berger wrote:
>> 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?
> Try and enable the feature, if it fails then there is no feature in
> the kernel.
> This is the usual way to add new syscalls..
>>> 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.
> Well, if TIS hardware has some scheme I feel like the emulator uAPI should
> have enough fidelity to ecompass existing hardware, even if your
> current emulator does not need it.
> So allowing request_locality to fail from userspace seems reasonable.

What's the best interface to use for this ?

  reply	other threads:[~2017-05-04 17:28 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-04 14:56 [PATCH v3 0/3] Extend the vTPM proxy driver to pass locality Stefan Berger
     [not found] ` <>
2017-05-04 14:56   ` [PATCH v3 1/3] tpm: vtpm_proxy: Implement new ioctl to get supported flags Stefan Berger
     [not found]     ` <>
2017-05-04 15:34       ` Jason Gunthorpe
2017-05-04 17:13         ` Stefan Berger
2017-05-04 17:20           ` Jason Gunthorpe
2017-05-04 17:28             ` Stefan Berger [this message]
2017-05-04 17:31               ` Jason Gunthorpe
2017-05-04 17:33                 ` Stefan Berger
2017-05-04 14:56   ` [PATCH v3 2/3] tpm: vtpm_proxy: Implement request_locality function Stefan Berger
2017-05-04 14:56 ` [PATCH v3 3/3] tpm: vtpm_proxy: Add flag for ioctl to request locality prepended to command Stefan Berger

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