linux-kernel - Re: [PATCH v22 04/24] x86/cpu/intel: Detect SGX supprt

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Message-ID: <20190924161301.GI19317@zn.tnic>
Date:   Tue, 24 Sep 2019 18:13:01 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-sgx@...r.kernel.org, akpm@...ux-foundation.org,
        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,
        andriy.shevchenko@...ux.intel.com, tglx@...utronix.de,
        kai.svahn@...el.com, josh@...htriplett.org, luto@...nel.org,
        kai.huang@...el.com, rientjes@...gle.com, cedric.xing@...el.com
Subject: Re: [PATCH v22 04/24] x86/cpu/intel: Detect SGX supprt

On Tue, Sep 03, 2019 at 05:26:35PM +0300, Jarkko Sakkinen wrote:
> From: Sean Christopherson <sean.j.christopherson@...el.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.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Co-developed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> ---
>  arch/x86/kernel/cpu/intel.c | 39 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> index 8d6d92ebeb54..777ea63b4f85 100644
> --- a/arch/x86/kernel/cpu/intel.c
> +++ b/arch/x86/kernel/cpu/intel.c
> @@ -623,6 +623,42 @@ static void detect_tme(struct cpuinfo_x86 *c)
>  	c->x86_phys_bits -= keyid_bits;
>  }
>  
> +static void __maybe_unused 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: The feature control MSR is not locked\n");
> +		goto err_unsupported;
> +	}
> +
> +	if (!(fc & FEATURE_CONTROL_SGX_ENABLE)) {
> +		pr_err_once("sgx: SGX is not enabled in IA32_FEATURE_CONTROL MSR\n");
> +		goto err_unsupported;
> +	}
> +
> +	if (!cpu_has(c, X86_FEATURE_SGX1)) {
> +		pr_err_once("sgx: SGX1 instruction set is not supported\n");
> +		goto err_unsupported;
> +	}
> +
> +	if (!(fc & FEATURE_CONTROL_SGX_LE_WR)) {
> +		pr_info_once("sgx: The launch control MSRs are not writable\n");
> +		goto err_msrs_rdonly;
> +	}
> +
> +	return;
> +
> +err_unsupported:
> +	setup_clear_cpu_cap(X86_FEATURE_SGX);
> +	setup_clear_cpu_cap(X86_FEATURE_SGX1);
> +	setup_clear_cpu_cap(X86_FEATURE_SGX2);
> +
> +err_msrs_rdonly:
> +	setup_clear_cpu_cap(X86_FEATURE_SGX_LC);
> +}
> +
>  static void init_cpuid_fault(struct cpuinfo_x86 *c)
>  {
>  	u64 msr;
> @@ -760,6 +796,9 @@ static void init_intel(struct cpuinfo_x86 *c)
>  	if (cpu_has(c, X86_FEATURE_TME))
>  		detect_tme(c);
>  
> +	if (IS_ENABLED(CONFIG_INTEL_SGX) && cpu_has(c, X86_FEATURE_SGX))
> +		detect_sgx(c);

Looks to me like this should run only once on the BSP instead of on
every CPU. The pr_*_once things above are a good sign for that, I'd say.

If so, define your own ->c_bsp_init function and run that from there
instead.

-- 
Regards/Gruss,
    Boris.

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