linux-kernel - Re: [tpmdd-devel] [PATCH] tpm: remove chip

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Message-ID: <20171024173757.GA1806@obsidianresearch.com>
Date:   Tue, 24 Oct 2017 11:37:57 -0600
From:   Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     PrasannaKumar Muralidharan <prasannatsmkumar@...il.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        linux-integrity@...r.kernel.org,
        David Howells <dhowells@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "open list:INTEGRITY MEASUREMENT ARCHITECTURE IMA" 
        <linux-ima-user@...ts.sourceforge.net>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        open list <linux-kernel@...r.kernel.org>,
        linux-security-module@...r.kernel.org,
        "moderated list:TPM DEVICE DRIVER" 
        <tpmdd-devel@...ts.sourceforge.net>,
        "open list:KEYS-TRUSTED" <keyrings@...r.kernel.org>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>,
        James Morris <james.l.morris@...cle.com>,
        Matt Mackall <mpm@...enic.com>,
        "open list:INTEGRITY MEASUREMENT ARCHITECTURE IMA" 
        <linux-ima-devel@...ts.sourceforge.net>,
        David Safford <safford@...ibm.com>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        "Serge E. Hallyn" <serge@...lyn.com>
Subject: Re: [tpmdd-devel] [PATCH] tpm: remove chip_num parameter from
 in-kernel API

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

Makes sense

> TPM core should register HWRNGs when chips are ready.

The main thing I've wanted from the TPM RNG is
'add_early_randomness'..

We can certainly provide a TPM interface to hwrng, it seems
reasonable.

Excep that we already have a user api in /dev/tpm to access the
tpm RNG, is the duplication a problem?

Jason