linux-kernel - Re: [PATCH v17 06/23] x86/cpu/intel: Detect SGX support and update caps appropriately

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Date:   Sun, 18 Nov 2018 10:37:28 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     x86@...nel.org, platform-driver-x86@...r.kernel.org,
        linux-sgx@...r.kernel.org, sean.j.christopherson@...el.com,
        nhorman@...hat.com, npmccallum@...hat.com, serge.ayoun@...el.com,
        shay.katz-zamir@...el.com, haitao.huang@...ux.intel.com,
        andriy.shevchenko@...ux.intel.com, tglx@...utronix.de,
        kai.svahn@...el.com, mark.shanahan@...el.com, luto@...capital.net,
        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>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        David Wang <davidwang@...oxin.com>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>,
        Jia Zhang <qianyue.zj@...baba-inc.com>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v17 06/23] x86/cpu/intel: Detect SGX support and update
 caps appropriately

On Fri, Nov 16, 2018 at 03:32:36PM -0800, Dave Hansen wrote:
> On 11/15/18 5:01 PM, Jarkko Sakkinen wrote:
> > +static void detect_sgx(struct cpuinfo_x86 *c)
> > +{
> > +	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");
> > +		goto out_unsupported;
> > +	}
> 
> This needs a check against the config option somewhere so the compiler
> can toss it in its entirety if SGX is config'd out.

Certainly. I'll flag it in the next version.

/Jarkko