Re: [tpmdd-devel] [PATCH] tpm: remove chip_num parameter from in-kernel API

[Peter Huewe]

Am 24. Oktober 2017 20:15:12 MESZ schrieb Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>:
>On Tue, Oct 24, 2017 at 10:02:00AM -0700, Dmitry Torokhov wrote:
>> On Tue, Oct 24, 2017 at 9:11 AM, Jason Gunthorpe
>> <jgunthorpe@xxxxxxxxxxxxxxxxxxxx> wrote:
>> > On Tue, Oct 24, 2017 at 09:37:33PM +0530, PrasannaKumar
>Muralidharan wrote:
>> >> Hi Jason,
>> >>
>> >> On 24 October 2017 at 21:25, Jason Gunthorpe
>> >> <jgunthorpe@xxxxxxxxxxxxxxxxxxxx> wrote:
>> >> > On Tue, Oct 24, 2017 at 09:21:15PM +0530, PrasannaKumar
>Muralidharan wrote:
>> >> >
>> >> >> Please check the RFC [1]. It does use chip id. The rfc has
>issues and
>> >> >> 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
>> >> > the hwrng, not parse a string.
>> >>
>> >> The drivers/char/hw_random/tpm-rng.c module does not store the
>chip
>> >> reference so I guess the usage is safe.
>> >
>> > It is using the default TPM, it is always safe to use the default
>tpm.
>> 
>> 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,
>> 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

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