linux-kernel - RE: [PATCH v2 2/4] tpm: Simplify locality handling

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Message-ID: <42097d7cc31c4cf495d1f8b46b3587af@infineon.com>
Date:   Wed, 28 Apr 2021 07:13:28 +0000
From:   <Peter.Huewe@...ineon.com>
To:     <jarkko@...nel.org>, <LinoSanfilippo@....de>
CC:     <peterhuewe@....de>, <jgg@...pe.ca>, <stefanb@...ux.vnet.ibm.com>,
        <James.Bottomley@...senpartnership.com>, <keescook@...omium.org>,
        <jsnitsel@...hat.com>, <ml.linux@...oe.vision>,
        <linux-integrity@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 2/4] tpm: Simplify locality handling

On Mon, Apr 26, 2021 at 01:47:18AM +0200, Lino Sanfilippo wrote:
> Currently the TPM (default) locality is claimed and released for each 
> access to the TPM registers which require a claimed locality. This 
> results in locality claim/release combos at various code places. For 
> interrupt handling we also need such a combo in the interrupt handler 
> (for clearing the interrupts) which makes the locality handling even 
> more complicated since now we also have to synchronize concurrent 
> accesses in process and in interrupt context.
>
> Since currently the driver uses only one locality anyway, avoid the 
> increasing complexity by claiming it once at driver startup and only 
> releasing it at driver shutdown.
>
> Due to the simplifications the functions tpm_request_locality() and
> tpm_relinquish_locality() are not needed any more an can be removed.
>

+1
I like the idea, as it also improves performance a bit.
Peter