From: Mario Limonciello <mario.limonciello@amd.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
Jarkko Sakkinen <jarkko@kernel.org>
Cc: Daniil Stas <daniil.stas@posteo.net>,
James.Bottomley@hansenpartnership.com, Jason@zx2c4.com,
linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
regressions@leemhuis.info, stable@vger.kernel.org
Subject: Re: [PATCH 1/1] tpm: disable hwrng for fTPM on some AMD designs
Date: Tue, 1 Aug 2023 13:51:49 -0500 [thread overview]
Message-ID: <6a80d9e9-aec9-2cbd-d65b-bb1e84b77b2b@amd.com> (raw)
In-Reply-To: <CAHk-=wgK0Z-LrJGExwG=e=oxjD93LJhY3jMmi_2O2_Pkjf8Tsg@mail.gmail.com>
On 8/1/2023 13:42, Linus Torvalds wrote:
> On Tue, 1 Aug 2023 at 11:28, Jarkko Sakkinen <jarkko@kernel.org> wrote:
>>
>> I would disable it inside tpm_crb driver, which is the driver used
>> for fTPM's: they are identified by MSFT0101 ACPI identifier.
>>
>> I think the right scope is still AMD because we don't have such
>> regressions with Intel fTPM.
>
> I'm ok with that.
>
>> I.e. I would move the helper I created inside tpm_crb driver, and
>> a new flag, let's say "TPM_CHIP_FLAG_HWRNG_DISABLED", which tpm_crb
>> sets before calling tpm_chip_register().
>>
>> Finally, tpm_add_hwrng() needs the following invariant:
>>
>> if (chip->flags & TPM_CHIP_FLAG_HWRNG_DISABLED)
>> return 0;
>>
>> How does this sound? I can refine this quickly from my first trial.
>
> Sounds fine.
This sounds fine by me too, thanks.
>
> My only worry comes from my ignorance: do these fTPM devices *always*
> end up being enumerated through CRB, or do they potentially look
> "normal enough" that you can actually end up using them even without
> having that CRB driver loaded?
>
> Put another way: is the CRB driver the _only_ way they are visible, or
> could some people hit on this through the TPM TIS interface if they
> have CRB disabled?
>
> I see, for example, that qemu ends up emulating the TIS layer, and it
> might end up forwarding the TPM requests to something that is natively
> CRB?
>
> But again: I don't know enough about CRB vs TIS, so the above may be a
> stupid question.
>
> Linus
next prev parent reply other threads:[~2023-08-01 18:51 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-14 20:19 [PATCH 0/1] Avoid triggering an fTPM bug from kernel Mario Limonciello
2023-02-14 20:19 ` [PATCH 1/1] tpm: disable hwrng for fTPM on some AMD designs Mario Limonciello
2023-02-17 15:18 ` Thorsten Leemhuis
2023-02-17 22:35 ` Jarkko Sakkinen
2023-02-18 2:25 ` Limonciello, Mario
2023-02-21 22:53 ` Jarkko Sakkinen
2023-02-21 23:10 ` Limonciello, Mario
2023-02-27 10:57 ` Thorsten Leemhuis
2023-02-27 11:14 ` Jarkko Sakkinen
2023-02-27 11:16 ` Jarkko Sakkinen
2023-02-17 22:05 ` Jarkko Sakkinen
2023-07-27 15:38 ` Daniil Stas
2023-07-27 15:42 ` Mario Limonciello
2023-07-27 16:39 ` Daniil Stas
2023-07-27 16:41 ` Mario Limonciello
2023-07-27 16:50 ` Daniil Stas
2023-07-27 16:51 ` Mario Limonciello
2023-07-27 17:05 ` Daniil Stas
2023-07-28 20:41 ` Linus Torvalds
2023-07-28 21:01 ` Limonciello, Mario
2023-07-28 21:38 ` Linus Torvalds
2023-07-28 21:47 ` Limonciello, Mario
[not found] ` <CUGAV1Y993FB.1O2Q691015Z2C@seitikki>
2023-07-31 19:05 ` Linus Torvalds
2023-07-31 19:18 ` Limonciello, Mario
2023-07-31 19:30 ` Linus Torvalds
2023-07-31 21:57 ` Limonciello, Mario
2023-07-31 23:28 ` Linus Torvalds
2023-07-31 23:40 ` Jason A. Donenfeld
2023-08-01 3:04 ` Mario Limonciello
2023-08-01 11:36 ` Mateusz Schyboll
2023-08-01 18:52 ` Jarkko Sakkinen
2023-08-01 18:55 ` Jarkko Sakkinen
2023-08-01 18:28 ` Jarkko Sakkinen
2023-08-01 18:42 ` Linus Torvalds
2023-08-01 18:51 ` Mario Limonciello [this message]
2023-08-01 19:09 ` Jarkko Sakkinen
2023-08-02 23:13 ` Jerry Snitselaar
2023-08-03 0:34 ` Stefan Berger
2023-07-31 21:44 ` Limonciello, Mario
2023-07-28 19:30 ` Jarkko Sakkinen
2023-07-28 20:18 ` Daniil Stas
2023-07-31 10:14 ` Jarkko Sakkinen
2023-07-31 10:28 ` Daniil Stas
2023-07-31 11:07 ` Jarkko Sakkinen
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