linux-kernel - Re: [PATCH v38 13/24] x86/sgx: Add SGX_IOC_ENCLAVE_ADD

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Date:   Mon, 21 Sep 2020 22:44:19 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Haitao Huang <haitao.huang@...ux.intel.com>, x86@...nel.org,
        linux-sgx@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jethro Beekman <jethro@...tanix.com>,
        Chunyang Hui <sanqian.hcy@...fin.com>,
        Jordan Hand <jorhand@...ux.microsoft.com>,
        Nathaniel McCallum <npmccallum@...hat.com>,
        Seth Moore <sethmo@...gle.com>,
        Darren Kenny <darren.kenny@...cle.com>,
        Suresh Siddha <suresh.b.siddha@...el.com>,
        akpm@...ux-foundation.org, andriy.shevchenko@...ux.intel.com,
        asapek@...gle.com, bp@...en8.de, cedric.xing@...el.com,
        chenalexchen@...gle.com, conradparker@...gle.com,
        cyhanish@...gle.com, dave.hansen@...el.com, haitao.huang@...el.com,
        josh@...htriplett.org, kai.huang@...el.com, kai.svahn@...el.com,
        kmoy@...gle.com, ludloff@...gle.com, luto@...nel.org,
        nhorman@...hat.com, puiterwijk@...hat.com, rientjes@...gle.com,
        tglx@...utronix.de, yaozhangx@...gle.com
Subject: Re: [PATCH v38 13/24] x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES

On Mon, Sep 21, 2020 at 09:49:48PM +0300, Jarkko Sakkinen wrote:
> To have understandable semantics you have to map error codes to
> conditions rather than opcodes. -EIO means loss of enclave in the event
> of EPC gone invalid. Enclave is already lost, that is the reason why we
> deinitialize the kernel data structures.
> 
> EADD must have a different error code because nothing is actually lost
> but the failure conditions are triggered outside. -EFAULT would be
> probably the most reasonable choice for that.

Now that I did all the changes discussed and then I remember why EADD
and EEXTEND had a common error code, and common behaviour. Obviously EADD
can also fail because of EPC reset because it depends on a valid SECS
page.

If we cannot distinct from EADD caused by EPC loss and EADD caused by
problems with the source, it should have the same error code, and also
the enclave should be deinitialized, whenver this happens.

So I would just revert to v38 behaviour, keeping of course the whole
check more visible in sgx_ioc_enclave_add_pages(), and just refine
the documentation better describe the whole situation.

/Jarkko