linux-kernel - Re: [PATCH v22 09/24] x86/sgx: Add functions to allocate and free EPC pages

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Date:   Tue, 8 Oct 2019 11:09:31 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-sgx@...r.kernel.org, akpm@...ux-foundation.org,
        dave.hansen@...el.com, nhorman@...hat.com, npmccallum@...hat.com,
        serge.ayoun@...el.com, shay.katz-zamir@...el.com,
        haitao.huang@...el.com, andriy.shevchenko@...ux.intel.com,
        tglx@...utronix.de, kai.svahn@...el.com, josh@...htriplett.org,
        luto@...nel.org, kai.huang@...el.com, rientjes@...gle.com,
        cedric.xing@...el.com
Subject: Re: [PATCH v22 09/24] x86/sgx: Add functions to allocate and free
 EPC pages

On Mon, Oct 07, 2019 at 07:50:11AM -0700, Sean Christopherson wrote:
> The caller is responsible for ensuring EREMOVE can be safely executed,
> e.g. by holding the enclave's lock.

lockdep_assert_held() here maybe?

> For many ENCLS leafs, EREMOVE included, the CPU requires exclusive access
> to the SGX Enclave Control Structures (SECS)[*] and will signal a #GP if
> a different logical CPU is already executing an ENCLS leaf that requires
> exclusive SECS access.  The SGX subsystem uses a per-enclave mutex to
> serialize such ENCLS leafs, among other things.
>
> [*] The SECS is a per-enclave page that resides in the EPC and can only be
>     directly accessed by the CPU.  It's used to track metadata about the
>     enclave, e.g. number of child pages, base, size, etc...

Ok.

-- 
Regards/Gruss,
    Boris.

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