linux-kernel - Re: [PATCH v26 10/22] x86/sgx: Linux Enclave Driver

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Date:   Sat, 15 Feb 2020 09:32:34 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Jethro Beekman <jethro@...tanix.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-sgx@...r.kernel.org, akpm@...ux-foundation.org,
        dave.hansen@...el.com, sean.j.christopherson@...el.com,
        nhorman@...hat.com, npmccallum@...hat.com, haitao.huang@...el.com,
        andriy.shevchenko@...ux.intel.com, tglx@...utronix.de,
        kai.svahn@...el.com, bp@...en8.de, josh@...htriplett.org,
        luto@...nel.org, kai.huang@...el.com, rientjes@...gle.com,
        cedric.xing@...el.com, puiterwijk@...hat.com,
        linux-security-module@...r.kernel.org,
        Suresh Siddha <suresh.b.siddha@...el.com>,
        Haitao Huang <haitao.huang@...ux.intel.com>
Subject: Re: [PATCH v26 10/22] x86/sgx: Linux Enclave Driver

On Thu, Feb 13, 2020 at 02:59:52PM +0100, Jethro Beekman wrote:
> Besides only partially measuring a page, there are some other fringe
> cases that are technically possible, although I haven't seen any
> toolchains that do that. These include not interleaving EADD and
> EEXTEND, not using logical ordering for the EEXTENDs, and call EEXTEND
> multiple times on the same chunk. Maximum interoperability would
> require supporting any EADD/EEXTEND sequence.

The reason why EEXTEND deals with chunks is nothing to do with the
granularity but just to amortize the algorithm. I did ask about this
and this is the answer that I got.

I think it is perfectly sane for Linux to define ABI here in at this
level.

> Tested-by: Jethro Beekman <jethro@...tanix.com>

Thanks you.

> Sorry for being super late with this, I know you asked me for feedback
> about this specific point in October. However, I did previously
> mention several times that being able to measure individual 256-byte
> chunks is necessary.

NP.

/Jarkko