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Virtualization of Intel SGX depends on Enclave Page Cache (EPC) management that is not yet available in the kernel, i.e. KVM support for exposing SGX to a guest cannot be added until basic support for SGX is upstreamed, which is a WIP[1]. Until SGX is properly supported in KVM, ensure a guest sees expected behavior for ENCLS, i.e. all ENCLS #UD. Because SGX does not have a true software enable bit, e.g. there is no CR4.SGXE bit, the ENCLS instruction can be executed[1] by the guest if SGX is supported by the system. Intercept all ENCLS leafs (via the ENCLS- exiting control and field) and unconditionally inject #UD. [1] https://www.spinics.net/lists/kvm/msg171333.html or https://lkml.org/lkml/2018/7/3/879 [2] A guest can execute ENCLS in the sense that ENCLS will not take an immediate #UD, but no ENCLS will ever succeed in a guest without explicit support from KVM (map EPC memory into the guest), unless KVM has a *very* egregious bug, e.g. accidentally mapped EPC memory into the guest SPTEs. In other words this patch is needed only to prevent the guest from seeing inconsistent behavior, e.g. #GP (SGX not enabled in Feature Control MSR) or #PF (leaf operand(s) does not point at EPC memory) instead of #UD on ENCLS. Intercepting ENCLS is not required to prevent the guest from truly utilizing SGX. Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Message-Id: <20180814163334.25724-3-sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.