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 06:31:44 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Borislav Petkov <bp@...en8.de>
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 Tue, Oct 08, 2019 at 11:09:31AM +0200, Borislav Petkov wrote:
> 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?

There are a few flows where a page can be removed without holding a lock,
e.g. when the enclave is being released, and for Version Array (VA) pages,
which are not associated with a single enclave.  We could probably force
a lockdep assert with an extra parameter, but I'm not sure that'd be a net
positive.