linux-kernel - Re: [PATCH v13 10/13] x86/sgx: Add sgx

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Date:   Tue, 4 Sep 2018 19:05:09 +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 10/13] x86/sgx: Add sgx_einit() for initializing enclaves

On Mon, Aug 27, 2018 at 9:58 PM Jarkko Sakkinen
<jarkko.sakkinen@...ux.intel.com> wrote:
>
> From: Sean Christopherson <sean.j.christopherson@...el.com>
>
> Add a function to perform ENCLS(EINIT), which initializes an enclave,
> which can be used by a driver for running enclaves and VMMs.
>
> Writing the LE hash MSRs is extraordinarily expensive, e.g. 3-4x slower
> than normal MSRs, so we use a per-cpu cache to track the last known value
> of the MSRs to avoid unnecessarily writing the MSRs with the current value.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Co-developed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

> +int sgx_einit(struct sgx_sigstruct *sigstruct, struct sgx_einittoken *token,
> +             struct sgx_epc_page *secs_page, u64 lepubkeyhash[4]);

This [4] doesn't make any sense in a C when used in function call
parameter list.

> +/* The cache for the last known values of IA32_SGXLEPUBKEYHASHx MSRs for each
> + * CPU. The entries are initialized when they are first used by sgx_einit().
> + */
> +struct sgx_lepubkeyhash {
> +       u64 msrs[4];

4 is MAGIC.

> +       u64 pm_cnt;
> +};

> +int sgx_einit(struct sgx_sigstruct *sigstruct, struct sgx_einittoken *token,
> +             struct sgx_epc_page *secs_page, u64 lepubkeyhash[4])

Same two comments about [4].

> +{

> +       cache = per_cpu(sgx_lepubkeyhash_cache, smp_processor_id());

> +       if (!cache) {

How often it's being expected to happen?

> +               cache = kzalloc(sizeof(struct sgx_lepubkeyhash), GFP_KERNEL);
> +               if (!cache)
> +                       return -ENOMEM;
> +       }

> +       for (i = 0; i < 4; i++) {

Same MAGIC?

> +       }

> +}

-- 
With Best Regards,
Andy Shevchenko