KVM: vmx: Inject #UD for SGX ENCLS instruction in guest
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: NSean Christopherson <sean.j.christopherson@intel.com> Message-Id: <20180814163334.25724-3-sean.j.christopherson@intel.com> Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
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