linux-kernel - Re: [PATCH v15 05/23] x86/cpu/intel: Detect SGX support and update caps appropriately

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Date:   Sat, 3 Nov 2018 15:05:39 +0200
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>,
        linux-sgx@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>,
        sean.j.christopherson@...el.com, nhorman@...hat.com,
        npmccallum@...hat.com, serge.ayoun@...el.com,
        shay.katz-zamir@...el.com, haitao.huang@...el.com,
        mark.shanahan@...el.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        David Woodhouse <dwmw@...zon.co.uk>, davidwang@...oxin.com,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>,
        qianyue.zj@...baba-inc.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v15 05/23] x86/cpu/intel: Detect SGX support and update
 caps appropriately

On Sat, Nov 3, 2018 at 1:16 AM Jarkko Sakkinen
<jarkko.sakkinen@...ux.intel.com> wrote:
>
> From: Sean Christopherson <sean.j.christopherson@...el.com>
>
> Similar to other large Intel features such as VMX and TXT, SGX must be
> explicitly enabled in IA32_FEATURE_CONTROL MSR to be truly usable.
> Clear all SGX related capabilities if SGX is not fully enabled in
> IA32_FEATURE_CONTROL or if the SGX1 instruction set isn't supported
> (impossible on bare metal, theoretically possible in a VM if the VMM
> is doing something weird).
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/kernel/cpu/intel.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> index fc3c07fe7df5..9bf8fe2c04ac 100644
> --- a/arch/x86/kernel/cpu/intel.c
> +++ b/arch/x86/kernel/cpu/intel.c
> @@ -596,6 +596,30 @@ static void detect_tme(struct cpuinfo_x86 *c)
>         c->x86_phys_bits -= keyid_bits;
>  }
>
> +static void detect_sgx(struct cpuinfo_x86 *c)
> +{
> +       bool unsupported = false;
> +       unsigned long long fc;
> +
> +       rdmsrl(MSR_IA32_FEATURE_CONTROL, fc);
> +       if (!(fc & FEATURE_CONTROL_LOCKED)) {
> +               pr_err_once("sgx: IA32_FEATURE_CONTROL MSR is not locked\n");
> +               unsupported = true;
> +       } else if (!(fc & FEATURE_CONTROL_SGX_ENABLE)) {
> +               pr_err_once("sgx: not enabled in IA32_FEATURE_CONTROL MSR\n");
> +               unsupported = true;
> +       } else if (!cpu_has(c, X86_FEATURE_SGX1)) {
> +               pr_err_once("sgx: SGX1 instruction set not supported\n");
> +               unsupported = true;
> +       }

If you do

} else {
 /* Supported */
 return;
}

here, you may get rid of temporary variable.

(Up to you)

> +
> +       if (unsupported) {
> +               setup_clear_cpu_cap(X86_FEATURE_SGX);
> +               setup_clear_cpu_cap(X86_FEATURE_SGX1);
> +               setup_clear_cpu_cap(X86_FEATURE_SGX2);
> +       }
> +}
> +
>  static void init_intel_energy_perf(struct cpuinfo_x86 *c)
>  {
>         u64 epb;
> @@ -763,6 +787,9 @@ static void init_intel(struct cpuinfo_x86 *c)
>         if (cpu_has(c, X86_FEATURE_TME))
>                 detect_tme(c);
>
> +       if (cpu_has(c, X86_FEATURE_SGX))
> +               detect_sgx(c);
> +
>         init_intel_energy_perf(c);
>
>         init_intel_misc_features(c);
> --
> 2.19.1
>


-- 
With Best Regards,
Andy Shevchenko