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Message-ID: <20d3cc40d559a854a7984543acdacb61a2d51b8d.camel@linux.intel.com>
Subject: Re: [PATCH v28 21/22] x86/vdso: Implement a vDSO for Intel SGX
 enclave call
From:   Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To:     Nathaniel McCallum <npmccallum@redhat.com>,
        Jethro Beekman <jethro@fortanix.com>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        linux-sgx@vger.kernel.org, akpm@linux-foundation.org,
        dave.hansen@intel.com,
        "Christopherson, Sean J" <sean.j.christopherson@intel.com>,
        Neil Horman <nhorman@redhat.com>,
        "Huang, Haitao" <haitao.huang@intel.com>,
        andriy.shevchenko@linux.intel.com, tglx@linutronix.de,
        "Svahn, Kai" <kai.svahn@intel.com>, bp@alien8.de,
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        Connor Kuehl <ckuehl@redhat.com>,
        Harald Hoyer <harald@redhat.com>,
        Lily Sturmann <lsturman@redhat.com>
Date:   Mon, 16 Mar 2020 23:27:03 +0200
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On Mon, 2020-03-16 at 09:57 -0400, Nathaniel McCallum wrote:
> For the vDSO, only marginally. I'm counting +4,-2 instructions in my
> suggestions. For the wrapper, things become significantly simpler.

Simpler is not a quality that has very high importance here except
when it comes to vDSO.

At least it is not enough to change to vDSO. What else?

Anyway, I think the documentation should fixed and streamlined 1st.

It is way too verbose prose in some places and in some it completely
lacks the information e.g.

"Debug Exceptions (#DB) and Breakpoints (#BP) are ever fixed up and are
always delivered via standard signals."

Never should state things like that without explaining the reasons.

On the other hand:

"Most exceptions reported on ENCLU, including those that occur within
the enclave, are fixed up and reported synchronously instead of being
delivered via a standard signal. Debug Exceptions (#DB) and Breakpoints
(#BP) are never fixed up and are always delivered via standard signals.
On synchrously reported exceptions, -EFAULT is returned and details
about the exception are recorded in @e, the optional
sgx_enclave_exception struct."

Duplicates information already elsewhere (e.g. return values) and is
just pain to read and comprehend in general.

/Jarkko