linux-kernel - Re: [PATCH v13 09/13] x86/sgx: Enclave Page Cache (EPC) memory manager

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Date:   Mon, 3 Sep 2018 22:02:16 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        sean.j.christopherson@...el.com, nhorman@...hat.com,
        npmccallum@...hat.com, linux-sgx@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, suresh.b.siddha@...el.com,
        serge.ayoun@...el.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v13 09/13] x86/sgx: Enclave Page Cache (EPC) memory manager

On Mon, Aug 27, 2018 at 9:58 PM Jarkko Sakkinen
<jarkko.sakkinen@...ux.intel.com> wrote:
>
> Add a Enclave Page Cache (EPC) memory manager that can be used to
> allocate and free EPC pages. The swapper thread ksgxswapd reclaims pages
> on the event when the number of free EPC pages goes below
> %SGX_NR_LOW_PAGES up until it reaches %SGX_NR_HIGH_PAGES.
>
> Pages are reclaimed in LRU fashion from a global list. The consumers
> take care of calling EBLOCK (block page from new accesses), ETRACK
> (restart counting the entering hardware threads) and EWB (write page to
> the regular memory) because executing these operations usually (if not
> always) requires to do some subsystem-internal locking operations.

> +                       list_del(&page->list);

Is this page will be completely gone? Otherwise it might be needed to
reinit list head here as well.

> +       WARN(ret < 0, "sgx: cannot free page, reclaim in-progress");
> +       WARN(ret > 0, "sgx: EREMOVE returned %d (0x%x)", ret, ret);

I'm not sure (though it's easy to check) that you need sgx: prefix
here. WARN() might take pr_fmt() if defined.

-- 
With Best Regards,
Andy Shevchenko