linux-kernel - Re: [PATCH 4/4] selftests/sgx: Trigger the reclaimer and #PF handler

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Date:   Wed, 7 Jul 2021 02:50:16 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Reinette Chatre <reinette.chatre@...el.com>
Cc:     Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
        linux-sgx@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] selftests/sgx: Trigger the reclaimer and #PF handler

On Tue, Jul 06, 2021 at 11:34:54AM -0700, Reinette Chatre wrote:
> Hi Jarkko,
> 
> On 7/5/2021 7:36 AM, Jarkko Sakkinen wrote:
> > Create a heap for the test enclave, which has the same size as all
> > available Enclave Page Cache (EPC) pages in the system. This will guarantee
> > that all test_encl.elf pages *and* SGX Enclave Control Structure (SECS)
> > have been swapped out by the page reclaimer during the load time. Actually,
> > this adds a bit more stress than that since part of the EPC gets reserved
> > for the Version Array (VA) pages.
> > 
> > For each test, the page fault handler gets triggered in two occasions:
> > 
> > - When SGX_IOC_ENCLAVE_INIT is performed, SECS gets swapped in by the
> >    page fault handler.
> > - During the execution, each page that is referenced gets swapped in
> >    by the page fault handler.
> > 
> 
> If I understand this correctly, all EPC pages are now being consumed during
> fixture setup and thus every SGX test, no matter how big or small, now
> becomes a stress test of the reclaimer instead of there being a unique
> reclaimer test. Since an enclave is set up and torn down for every test this
> seems like a significant addition. It also seems like this would impact
> future tests of dynamic page addition where not all scenarios could be
> tested with all EPC pages already consumed.
> 
> Reinette

Re-initializing the test enclave is mandatory thing to do for all tests
because it has an internals state.

/Jarkko