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Subject: Re: [PATCH v4 2/6] tpm, tpm_tis: Claim and release locality only once
To:     Jarkko Sakkinen <jarkko@kernel.org>
Cc:     peterhuewe@gmx.de, jgg@ziepe.ca, stefanb@linux.vnet.ibm.com,
        linux@mniewoehner.de, linux-integrity@vger.kernel.org,
        linux-kernel@vger.kernel.org, lukas@wunner.de,
        p.rosenberger@kunbus.com, Lino Sanfilippo <l.sanfilippo@kunbus.com>
References: <20220509080559.4381-1-LinoSanfilippo@gmx.de>
 <20220509080559.4381-3-LinoSanfilippo@gmx.de> <YnudhZZGXf87U3bd@kernel.org>
 <f576a24d-d175-0153-9992-f6dd80d57b62@gmx.de> <Yn6cjJTj1SdS73pY@kernel.org>
From:   Lino Sanfilippo <LinoSanfilippo@gmx.de>
Message-ID: <dd421552-40f8-b5c2-5d5a-cc9ce3bdb760@gmx.de>
Date:   Mon, 16 May 2022 22:23:54 +0200
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On 13.05.22 at 19:59, Jarkko Sakkinen wrote:
> On Wed, May 11, 2022 at 09:29:57PM +0200, Lino Sanfilippo wrote:
>>
>>
>> On 11.05.22 at 13:27, Jarkko Sakkinen wrote:
>>> On Mon, May 09, 2022 at 10:05:55AM +0200, Lino Sanfilippo wrote:
>>>> From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>>>>
>>>> It is not necessary to claim and release the default locality for eac=
h TPM
>>>> command. Instead claim the locality once at driver startup and releas=
e it
>>>> at driver shutdown.
>>>>
>>>> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>>>
>>> We are doing what we're being because of Intel TXT:
>>>
>>> https://lore.kernel.org/tpmdd-devel/20170315055738.11088-1-jarkko.sakk=
inen@iki.fi/
>>>
>>> Unfortunately cannot accept this change.
>>>
>>
>> I do not see how the patch affects the crb code since the only changes =
concern the
>> tpm_class_ops of the tis core. AFAICS crb uses its own set of tpm_class=
_ops
>> which are still used to claim and release the locality.
>>
>> Or do I miss something?
>
> Ugh, yes breaking everything when TXT is used with tpm_tis.
>
>> Regards,
>> Lino
>
> BR, Jarkko
>

Ok, I got it now. The idea of this patch was to maintain the locality 0 fo=
r the whole
driver lifetime, so that we can always be sure that the locality is alread=
y claimed
when the interrupt status register is read or written in the interrupt han=
dler.

But of course this does not work if some other instance like TXT also want=
s
to claim localities.

I will try another approach to make sure that the locality is already take=
n when the
irq handler is called and only released after the handler has finished.

Regards,
Lino