Am 24. Oktober 2017 20:15:12 MESZ schrieb Jarkko Sakkinen [off-list ref]:

On Tue, Oct 24, 2017 at 10:02:00AM -0700, Dmitry Torokhov wrote:

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On Tue, Oct 24, 2017 at 9:11 AM, Jason Gunthorpe
[off-list ref] wrote:

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On Tue, Oct 24, 2017 at 09:37:33PM +0530, PrasannaKumar

Muralidharan wrote:

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Hi Jason,

On 24 October 2017 at 21:25, Jason Gunthorpe
[off-list ref] wrote:

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On Tue, Oct 24, 2017 at 09:21:15PM +0530, PrasannaKumar

Muralidharan wrote:

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Please check the RFC [1]. It does use chip id. The rfc has

issues and

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has to be fixed but still there could be users of the API.

1. https://www.spinics.net/lists/linux-crypto/msg28282.html

That patch isn't safe at all. You need to store a kref to th

chip in

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the hwrng, not parse a string.

The drivers/char/hw_random/tpm-rng.c module does not store the

chip

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reference so I guess the usage is safe.

It is using the default TPM, it is always safe to use the default

tpm.

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tpm-rng is abomination that should be kicked out as soon as possible.
It wrecks havoc with the power management (TPM chip drivers may go
into suspend state, but tpm_rng does not do any power management and
happily forwards requests to suspended hardware) and may be available
when there is no TPM at all yet (the drivers have not been probed

yet,

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or have gotten a deferral, etc).

TPM core should register HWRNGs when chips are ready.

Thanks.

-- 
Dmitry

I'm fine to review a two patch set where:

1. Patch 1 removes the existing TPM rng driver
2. Patch 2 makes the TPM driver as rng producer

Yes, but tpm must be kept a hwrng source.
This is imho an important use case.

Unrelate to patch that I'm proposing now but this sounds sensible.

/Jarkko

-- 
Sent from my mobile

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