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Kernel support for SGX is ultimately decided by the state of the launch control bits in the feature control MSR (MSR_IA32_FEAT_CTL). If the hardware supports SGX, but neglects to support flexible launch control, the kernel will not enable SGX. Enable SGX at feature control MSR initialization and update the associated X86_FEATURE flags accordingly. Disable X86_FEATURE_SGX (and all derivatives) if the kernel is not able to establish itself as the authority over SGX Launch Control. All checks are performed for each logical CPU (not just boot CPU) in order to verify that MSR_IA32_FEATURE_CONTROL is correctly configured on all CPUs. All SGX code in this series expects the same configuration from all CPUs. This differs from VMX where X86_FEATURE_VMX is intentionally cleared only for the current CPU so that KVM can provide additional information if KVM fails to load like which CPU doesn't support VMX. There’s not much the kernel or an administrator can do to fix the situation, so SGX neglects to convey additional details about these kinds of failures if they occur. Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Co-developed-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Jethro Beekman <jethro@fortanix.com> Link: https://lkml.kernel.org/r/20201112220135.165028-8-jarkko@kernel.org
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.