Re: [PATCH v24 07/24] x86/cpu/intel: Detect SGX supprt

From: Borislav Petkov <bp@alien8.de>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
	linux-sgx@vger.kernel.org, akpm@linux-foundation.org,
	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,
	andriy.shevchenko@linux.intel.com, tglx@linutronix.de,
	kai.svahn@intel.com, josh@joshtriplett.org, luto@kernel.org,
	kai.huang@intel.com, rientjes@google.com, cedric.xing@intel.com,
	puiterwijk@redhat.com
Subject: Re: [PATCH v24 07/24] x86/cpu/intel: Detect SGX supprt
Date: Tue, 17 Dec 2019 16:17:44 +0100	[thread overview]
Message-ID: <20191217151744.GG28788@zn.tnic> (raw)
In-Reply-To: <20191129231326.18076-8-jarkko.sakkinen@linux.intel.com>

On Sat, Nov 30, 2019 at 01:13:09AM +0200, Jarkko Sakkinen wrote:

Typo in the subject:

Subject: Re: [PATCH v24 07/24] x86/cpu/intel: Detect SGX supprt
							 ^^^^^^
> From: Sean Christopherson <sean.j.christopherson@intel.com>
> 
> When the CPU supports SGX, check that the BIOS has enabled SGX and SGX1
> opcodes are available. Otherwise, all the SGX related capabilities.
> 
> In addition, clear X86_FEATURE_SGX_LC also in the case when the launch
> enclave are read-only. This way the feature bit reflects the level that
> Linux supports the launch control.
> 
> The check is done for every CPU, not just BSP, in order to verify that
> MSR_IA32_FEATURE_CONTROL is correctly configured on all CPUs. The other
> parts of the kernel, like the enclave driver, expect the same
> configuration from all CPUs.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Co-developed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> ---
>  arch/x86/kernel/cpu/intel.c | 41 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)

...

> @@ -761,6 +797,11 @@ static void init_intel(struct cpuinfo_x86 *c)
>  	if (cpu_has(c, X86_FEATURE_TME))
>  		detect_tme(c);
>  
> +#ifdef CONFIG_INTEL_SGX
> +	if (cpu_has(c, X86_FEATURE_SGX))
> +		detect_sgx(c);
> +#endif

You can remove the ifdeffery here and put the ifdef around the function
body and drop the __maybe_unused tag:

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index ef41431b3f70..2f3414eff99d 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -624,8 +624,9 @@ static void detect_tme(struct cpuinfo_x86 *c)
 	c->x86_phys_bits -= keyid_bits;
 }
 
-static void __maybe_unused detect_sgx(struct cpuinfo_x86 *c)
+static void detect_sgx(struct cpuinfo_x86 *c)
 {
+#ifdef CONFIG_INTEL_SGX
 	unsigned long long fc;
 
 	rdmsrl(MSR_IA32_FEATURE_CONTROL, fc);
@@ -658,6 +659,7 @@ static void __maybe_unused detect_sgx(struct cpuinfo_x86 *c)
 
 err_msrs_rdonly:
 	setup_clear_cpu_cap(X86_FEATURE_SGX_LC);
+#endif
 }
 
 static void init_cpuid_fault(struct cpuinfo_x86 *c)
@@ -797,10 +799,8 @@ static void init_intel(struct cpuinfo_x86 *c)
 	if (cpu_has(c, X86_FEATURE_TME))
 		detect_tme(c);
 
-#ifdef CONFIG_INTEL_SGX
 	if (cpu_has(c, X86_FEATURE_SGX))
 		detect_sgx(c);
-#endif
 
 	init_intel_misc_features(c);
 

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette
