linux-kernel - Re: [PATCH v33 11/21] x86/sgx: Linux Enclave Driver

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Message-ID: <20200629153737.GA32176@zn.tnic>
Date:   Mon, 29 Jun 2020 17:37:37 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>, x86@...nel.org,
        linux-sgx@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Jethro Beekman <jethro@...tanix.com>,
        Haitao Huang <haitao.huang@...ux.intel.com>,
        Chunyang Hui <sanqian.hcy@...fin.com>,
        Jordan Hand <jorhand@...ux.microsoft.com>,
        Nathaniel McCallum <npmccallum@...hat.com>,
        Seth Moore <sethmo@...gle.com>,
        Suresh Siddha <suresh.b.siddha@...el.com>,
        akpm@...ux-foundation.org, andriy.shevchenko@...ux.intel.com,
        asapek@...gle.com, 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 v33 11/21] x86/sgx: Linux Enclave Driver

On Mon, Jun 29, 2020 at 08:27:19AM -0700, Sean Christopherson wrote:
> Hmm, I was going to say that SGX_ENCL_INITIALIZED can't be checked until
> encl->lock is held, but that's not true for this path as mutual exclusion
> is provided by the SGX_ENCL_IOCTL flag.  So yeah, this can be checked at
> the same time as SGX_ENCL_CREATED in sgx_ioc_enclave_init().

Right, so my point is to have state checks for flags which make sense in
all ioctl entry points, in order to catch a misuse early. But we're on
the same page.

> ENCLS[EINIT] is interruptible because it has such a high latency, e.g. 50k+
> cycles on success.  If an IRQ/NMI/SMI becomes pending, EINIT may fail with
> SGX_UNMASKED_EVENT so that the event can be serviced.
>
> The idea behind the double loop is to try EINIT in a tight loop, then back
> off and sleep for a while before retrying that tight inner loop.

That gist of that kinda wants to be in a comment over that double-loop for
future on-lookers.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette