linux-kernel - Re: [PATCH v3 1/4] tpm: Use a threaded interrupt handler

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Message-ID: <YJATRNMqzyAprCbL@kernel.org>
Date:   Mon, 3 May 2021 18:14:12 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Lino Sanfilippo <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,
        Stefan Berger <stefanb@...ux.ibm.com>
Subject: Re: [PATCH v3 1/4] tpm: Use a threaded interrupt handler

On Sat, May 01, 2021 at 03:57:24PM +0200, Lino Sanfilippo wrote:
> The interrupt handler uses tpm_tis_read32() and tpm_tis_write32() to access
> the interrupt status register. In case of SPI those accesses are done with
> the spi_bus_lock mutex held. This means that the status register cannot
> be read or written in interrupt context.
> 
> For this reason request a threaded interrupt handler so that the required
> accesses can be done in process context.
> 
> Reviewed-by: Stefan Berger <stefanb@...ux.ibm.com>
> Signed-off-by: Lino Sanfilippo <LinoSanfilippo@....de>

No fixes tag.

The short summary scopes now the whole TPM subsystem ("tpm:"), but the fix
is targetted *only* for tpm_tis_spi. How about "tpm, tpm_tis_spi: Allow to
sleep in the interrupt handler"?

This also changes the semantics tpm_tis_*, not just tpm_tis_spi, which is
not acceptable. We cannot backport a fix like this.

Probably you should just add a parameter to tpm_tis_core_init() to hint
that threaded IRQ is required, and then only conditionally do so.

/Jarkko