linux-kernel - Re: [PATCH] tpm/tpm_tis: Fix variable reset during IRQ probing

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Date:   Wed, 20 Jan 2021 12:03:49 +0800
From:   Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     Peter Huewe <peterhuewe@....de>, Jason Gunthorpe <jgg@...pe.ca>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jia Zhang <zhang.jia@...ux.alibaba.com>
Subject: Re: [PATCH] tpm/tpm_tis: Fix variable reset during IRQ probing



On 1/15/21 5:23 PM, Jarkko Sakkinen wrote:
> On Thu, Jan 14, 2021 at 12:12:16PM +0800, Tianjia Zhang wrote:
>>
>>
>> On 1/14/21 10:51 AM, Jarkko Sakkinen wrote:
>>> On Wed, Jan 13, 2021 at 08:00:21PM +0800, Tianjia Zhang wrote:
>>>> In tpm_tis_core_init(), tpm2_probe() will be called first, this
>>>> function will eventually call tpm_tis_send(), and then
>>>> tpm_tis_probe_irq_single() will detect whether the interrupt is
>>>> normal, mainly the installation interrupted, set `priv->irq_tested`
>>>> to false. The logic will eventually be executed to tpm_tis_send()
>>>> to trigger an interrupt.
>>>>
>>>> There is currently such a scenario, which will cause the IRQ probe
>>>> code to never be executed, so that the TPM device is in polling
>>>> mode: after setting irq_tested to false, an interrupt occurs
>>>> between entering the ttpm_tis_send() function, and the interrupt
>>>> will be first set irq_tested to true will cause the IRQ probe code
>>>> to never be executed.
>>>
>>> Can you describe the scenario more detail?
>>>
>>
>> The problematic scenario we encountered is like this. The following figure
>> shows the execution flow of tpm_tis_core_init(). An interrupt occurred
>> before the IRQ probe. This interrupt was caused by tpm2_probe(), but it was
>> triggered before the IRQ probe was executed, and the interrupt handler would
>> set irq_tested to true, so the IRQ probe code can never execute, that is,
>> the code marked 2 in the figure will never happen.
> 
> TPM_INT_ENABLE is cleared on reset [*].
> 
> [*] Section 5.9.1
>      https://trustedcomputinggroup.org/resource/pc-client-work-group-pc-client-specific-tpm-interface-specification-tis/
> 
> /Jarkko
> 

Hi,

I got it, this seems to be a firmware issue. Thanks for your reply.

Best regards,
Tianjia