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

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Message-ID: <20181105143140.GJ10650@smile.fi.intel.com>
Date:   Mon, 5 Nov 2018 16:31:40 +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, 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 Mon, Nov 05, 2018 at 04:09:33PM +0200, Jarkko Sakkinen wrote:
> On Sat, Nov 03, 2018 at 03:05:39PM +0200, Andy Shevchenko wrote:

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

LGTM.

> From 3b863a7db00cefffc15df918a5132c35ea313c27 Mon Sep 17 00:00:00 2001
> From: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> Date: Mon, 5 Nov 2018 16:06:06 +0200
> Subject: [PATCH] x86/cpu/intel: clean up detect_sgx() flow
> 
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> ---
>  arch/x86/kernel/cpu/intel.c | 32 ++++++++++++++++++++------------
>  1 file changed, 20 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> index bc52c52f7025..8a20a193d399 100644
> --- a/arch/x86/kernel/cpu/intel.c
> +++ b/arch/x86/kernel/cpu/intel.c
> @@ -598,28 +598,36 @@ static void detect_tme(struct cpuinfo_x86 *c)
>  
>  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)) {
> +		goto out_unsupported;
> +	}
> +
> +	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)) {
> +		goto out_unsupported;
> +	}
> +
> +	if (!cpu_has(c, X86_FEATURE_SGX1)) {
>  		pr_err_once("sgx: SGX1 instruction set not supported\n");
> -		unsupported = true;
> +		goto out_unsupported;
>  	}
>  
> -	if (unsupported) {
> -		setup_clear_cpu_cap(X86_FEATURE_SGX);
> -		setup_clear_cpu_cap(X86_FEATURE_SGX1);
> -		setup_clear_cpu_cap(X86_FEATURE_SGX2);
> +	if (!(fc & FEATURE_CONTROL_SGX_LE_WR)) {
> +		pr_info_once("sgx: launch control MSRs are not writable\n");
> +		goto out_msrs_rdonly;
>  	}
> -	if (unsupported || !(fc & FEATURE_CONTROL_SGX_LE_WR))
> -		setup_clear_cpu_cap(X86_FEATURE_SGX_LC);
> +
> +	return;
> +out_unsupported:
> +	setup_clear_cpu_cap(X86_FEATURE_SGX);
> +	setup_clear_cpu_cap(X86_FEATURE_SGX1);
> +	setup_clear_cpu_cap(X86_FEATURE_SGX2);
> +out_msrs_rdonly:
> +	setup_clear_cpu_cap(X86_FEATURE_SGX_LC);
>  }
>  
>  static void init_intel_energy_perf(struct cpuinfo_x86 *c)
> -- 
> 2.19.1
> 


-- 
With Best Regards,
Andy Shevchenko