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SubjectRe: [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@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.
>
> 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 | 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

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