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

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Date:   Mon, 5 Nov 2018 16:09:33 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Andy Shevchenko <andy.shevchenko@...il.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 03, 2018 at 03:05:39PM +0200, Andy Shevchenko wrote:
> > +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;
> }

Agree. Would this be a more clean flow in the attached patch?

/Jarkko

View attachment "0001-x86-cpu-intel-clean-up-detect_sgx-flow.patch" of type "text/x-diff" (2053 bytes)