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Date:   Mon, 5 Nov 2018 16:09:33 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>,
        Platform Driver <platform-driver-x86@vger.kernel.org>,
        linux-sgx@vger.kernel.org, Dave Hansen <dave.hansen@intel.com>,
        sean.j.christopherson@intel.com, nhorman@redhat.com,
        npmccallum@redhat.com, serge.ayoun@intel.com,
        shay.katz-zamir@intel.com, haitao.huang@intel.com,
        mark.shanahan@intel.com,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        David Woodhouse <dwmw@amazon.co.uk>, davidwang@zhaoxin.com,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com>,
        qianyue.zj@alibaba-inc.com,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v15 05/23] x86/cpu/intel: Detect SGX support and update
 caps appropriately
Message-ID: <20181105140933.GA24038@linux.intel.com>
References: <20181102231320.29164-1-jarkko.sakkinen@linux.intel.com>
 <20181102231320.29164-6-jarkko.sakkinen@linux.intel.com>
 <CAHp75VcG4FtiS9bDM_pP216kxobFxkChDu6uxvuTsMHQ=YJ3Zg@mail.gmail.com>
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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

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From 3b863a7db00cefffc15df918a5132c35ea313c27 Mon Sep 17 00:00:00 2001
From: Jarkko Sakkinen <jarkko.sakkinen@linux.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@linux.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


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