linux-kernel - Re: [PATCH v3 0/4] Fixes for TPM interrupt handling

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Message-ID: <77374443-dc9b-5d1d-c652-0d093b6029f4@gmx.de>
Date:   Sun, 24 Apr 2022 04:22:11 +0200
From:   Lino Sanfilippo <LinoSanfilippo@....de>
To:     Jarkko Sakkinen <jarkko@...nel.org>,
        Michael Niewöhner <linux@...ewoehner.de>
Cc:     peterhuewe@....de, jgg@...pe.ca, stefanb@...ux.vnet.ibm.com,
        stefanb@...ux.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,
        twawrzynczak@...omium.org, Lukas Wunner <lukas@...ner.de>,
        Philipp Rosenberger <p.rosenberger@...bus.com>
Subject: Re: [PATCH v3 0/4] Fixes for TPM interrupt handling


Hi,

On 20.04.22 at 07:30, Jarkko Sakkinen wrote:
> n Sat, 2022-03-26 at 04:24 +0100, Lino Sanfilippo wrote:
>>
>> Hi Michael,
>>
>> On 25.03.22 at 13:32, Michael Niewöhner wrote:
>>>>>
>>>>> Lino, I'd be happy to test the patches, when you have time and interest to
>>>>> work
>>>>> on this again!
>>>>>
>>>>> Thanks, Michael
>>>>
>>>> It's quite easy to test them out. Both fixes are in the mainline GIT tree.
>>>> E.g. give a shot rc1, and please report if any issues persists to:
>>>>
>>>>   linux-integrity@...r.kernel.org 
>>>>
>>>> BR, Jarkko
>>>
>>> I don't see Linos patches on mainline. Also, the series included four patches:
>>> [PATCH v3 0/4] Fixes for TPM interrupt handling
>>> [PATCH v3 1/4] tpm: Use a threaded interrupt handler
>>> [PATCH v3 2/4] tpm: Simplify locality handling
>>> [PATCH v3 3/4] tpm: Fix test for interrupts
>>> [PATCH v3 4/4] tpm: Only enable supported irqs
>>>
>>> Three of them are relevant for the interrupt problem, which is still present in
>>> mainline, as these patches were refused:
>>> [PATCH v3 1/4] tpm: Use a threaded interrupt handler
>>> [PATCH v3 2/4] tpm: Simplify locality handling
>>> [PATCH v3 3/4] tpm: Fix test for interrupts
>>>
>>> Michael
>>>
>>
>> You are right, the interrupts are still not working in the mainline kernel.
>> I would gladly make another attempt to fix this but rather step by step
>> than in a series that tries to fix (different) things at once.
>>
>> A first step could be to have a sleepable context for the interrupt handling,
>> since in case of SPI the accesses to the irq status register may sleep.
>>
>> I sent a patch for this purpose once, but it seems to have gone lost:
>>
>> https://lore.kernel.org/all/20210620023444.14684-1-LinoSanfilippo@gmx.de/
>>
>>
>> Best regards,
>> Lino
>
> I went these through one by one>
> # Above linked patch
>
> Boolean parameters are considered bad. I.e. use named flags
> instead. This is for above linked patch.

Ok, we could extend tpm_tis_flags by a flag "TPM_TIS_USE_THREADED_IRQ"
for this.

>
> # [PATCH v3 3/4] tpm: Fix test for interrupts
>
> 1. Please remove "unnecessarily complicated" sentence because
>    it cannot be evaluated. It's your opinion, which might perhaps
>    be correct, but it is irrelevant for any possible patch
>    description.
> 2. There's no such thing as "fix by re-implementation". Please
>    explain instead code change is relevant for the bug fix.
> 3. If set_bit() et al necessarily to fix a possible race condition
>    you need to have a separate patch for that.
>
> To move forward, start with a better summary such as
>
> "tpm: move interrupt test to tpm_tis_probe_irq_single()"
>
> I'd also either revert the change for flags, or alternatively
> move it to separate patch explaining race condition. Otherwise,
> there's no argument of saying that using set_bit() is more
> proper. This will make the change more localized.
>

Ok, I will split the fix for the irq test into two patches then.

>
> # [PATCH v3 2/4] tpm: Simplify locality handling
>
> "As a side-effect these modifications fix a bug which results in the
> following warning when using TPM 2:"
>
> Generally speaking, the simplifications should be done on top of code
> that does not have known bugs, even if the simplification renders out
> the bug. This is because then we have code that have potentially unknown
> unknown bugs.
>
> I hope you see my point. The problem with these patches were then
> and is still that they intermix bug fixes and other modifications and
> thus cannot be taken in.
>

Yes, I can see that point.

> BR, Jarkko
>

Thanks a lot for the review. I will prepare new patches with the suggested
changes.

Best regards,
Lino