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Date:   Wed, 17 Aug 2022 19:36:07 +0300
From:   Jarkko Sakkinen <jarkko@kernel.org>
To:     Reinette Chatre <reinette.chatre@intel.com>
Cc:     "Dhanraj, Vijay" <vijay.dhanraj@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
        Shuah Khan <shuah@kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] selftests/sgx: Add SGX selftest
 augment_via_eaccept_long
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On Wed, Aug 17, 2022 at 08:43:57AM -0700, Reinette Chatre wrote:
> Hi Jarkko,
> 
> On 8/17/2022 7:53 AM, Jarkko Sakkinen wrote:
> > On Wed, Aug 17, 2022 at 05:44:31PM +0300, Jarkko Sakkinen wrote:
> >> On Tue, Aug 16, 2022 at 09:35:27PM -0700, Reinette Chatre wrote:
> >>>>>> This portion below was also copied from previous test and by only
> >>>>>> testing a write to the first page of the range the purpose is not
> >>>>>> clear. Could you please elaborate if the intention is to only test
> >>>>>> accessibility of the first page and why that is sufficient?
> >>>>>
> >>>>> It is sufficient because the test reproduces the bug. It would have to be
> >>>>> rather elaborated why you would possibly want to do more than that.
> >>>
> >>> That is fair. An accurate comment (currently an inaccurate copy&paste) would
> >>> help to explain this part of the test.
> >>
> >> I would simply add something like:
> >>
> >> /* 
> >>  * Define memory pool size big enough to trigger the reclaimer in the EAUG
> >>  * path of the page reclaimer.
> >>  */
> >>
> >> Suggestions/edits obviously welcome for the comment.
> 
> The comment seems to better match the code below than the area referred to above:
>         static const unsigned long edmm_size = 8589934592; //8G
> 
> Even so, I think that raises the point that this is platform specific since
> edmm_size of 8GB would not trigger reclaimer on all platforms.
> 
> How about adjusting it to:
> /*
>  * Define memory pool size big enough to trigger the reclaimer in the EAUG
>  * path of the page reclaimer on some platforms. This constant has been
>  * successful in triggering a bug on some platforms (independent of the
>  * platforms where the reclaimer is triggered) and thus considered
>  * appropriate for general use.
>  */ 
> 
> 
> Regarding the area referred to above, a comment like below may help:
> 
> /*
>  * Pool of pages were successfully added to enclave. Perform sanity
>  * check on first page of the pool only to ensure data can be written
>  * to and read from a dynamically added enclave page.
>  */
> 
> > 
> > I wonder if we could put .bt files somewhere to make them available. In
> > root causing this bug bpftrace scripting was the key so it would nice to
> > have them available along with kselftest.
> > 
> > I could imagine that we end up also in future to bugs allocation so
> > it would have the script when you clone the kernel tree, and possibly
> > more scripts in future.
> > 
> > E.g. add bt/alloc-error.bt under tools/testing/selftests/sgx.
> 
> Thank you very much for helping to debug this issue. I also think
> the scripts you created are very valuable and making them easily
> accessible sounds great.

Yeah, I mean they do no harm there, even if not directly used
by the test program.

Thanks for the valuable feedback. I will incorporate it to the
next version.

BR, Jarkko