linux-kernel - Re: [PATCH v3] tpm: Add Upgrade/Reduced mode support for TPM2 modules

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Message-ID: <20210805205245.qcdqcuog7zmsp7j5@kernel.org>
Date:   Thu, 5 Aug 2021 23:52:45 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Borys Movchan <borysmn@...s.com>
Cc:     Peter Huewe <peterhuewe@....de>, Jason Gunthorpe <jgg@...pe.ca>,
        kernel@...s.com, linux-integrity@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] tpm: Add Upgrade/Reduced mode support for TPM2 modules

On Wed, Aug 04, 2021 at 06:21:31PM +0200, Borys Movchan wrote:
> If something went wrong during the TPM firmware upgrade, like power
> failure or the firmware image file get corrupted, the TPM might end
> up in Upgrade or Failure mode upon the next start. The state is
> persistent between the TPM power cycle/restart.
> 
> According to TPM specification:
>  * If the TPM is in Upgrade mode, it will answer with TPM2_RC_UPGRADE
>    to all commands except Field Upgrade related ones.
>  * If the TPM is in Failure mode, it will allow performing TPM
>    initialization but will not provide any crypto operations.
>    Will happily respond to Field Upgrade calls.
> 
> The fix changes the behavior of the `tpm2_auto_startup` function, so
                                
In commit messages, you ought to use imperative form:

"Change the behaviour of tpm2_auto_startup(), ..."

> it tries to detect what mode TPM is running in. If the chip is in the
> Upgrade or Failure mode, the function returns -EIO error code which
> can be used later to adjust driver behavior later.

*How* tpm2_auto_startup() detects the mode?

> After `tpm_chip_register` calls `tpm2_auto_startup` it checks for the

Please remove all these hyphens. They make the commit message a pain
to read. E.g. instead write tpm_chip_register(). This is not Github.

> error code. If the TPM is in Upgrade or Failure mode, set the
> `limited_mode` flag. The calls to `tpm2_get_cc_attrs_tbl`,
> `tpm_add_hwrng` and `tpm_get_pcr_allocation` will fail if the TPM is
> in Failure or Upgrade mode, so use `limited_mode` flag to exclude
> them from the module initialization sequence.
> 
> Signed-off-by: Borys Movchan <borysmn@...s.com>
> ---
> 
> Notes:
>     Commit message updated

v2:
* Commit message updated.

Notes would be something that had existed already in the first version.
Here we want a simple change log.

/Jarkko