KVM: VMX: Frame in ENCLS handler for SGX virtualization

Introduce sgx.c and sgx.h, along with the framework for handling ENCLS
VM-Exits.  Add a bool, enable_sgx, that will eventually be wired up to a
module param to control whether or not SGX virtualization is enabled at
runtime.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Kai Huang <kai.huang@intel.com>
Message-Id: <1c782269608b2f5e1034be450f375a8432fb705d.1618196135.git.kai.huang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/Makefile

@@ -23,6 +23,8 @@ kvm-$(CONFIG_KVM_XEN)	+= xen.o
 
 kvm-intel-y		+= vmx/vmx.o vmx/vmenter.o vmx/pmu_intel.o vmx/vmcs12.o \
 			   vmx/evmcs.o vmx/nested.o vmx/posted_intr.o
+kvm-intel-$(CONFIG_X86_SGX_KVM)	+= vmx/sgx.o
+
 kvm-amd-y		+= svm/svm.o svm/vmenter.o svm/pmu.o svm/nested.o svm/avic.o svm/sev.o
 
 obj-$(CONFIG_KVM)	+= kvm.o

arch/x86/kvm/vmx/sgx.c

@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0
+/*  Copyright(c) 2021 Intel Corporation. */
+
+#include <asm/sgx.h>
+
+#include "cpuid.h"
+#include "kvm_cache_regs.h"
+#include "sgx.h"
+#include "vmx.h"
+#include "x86.h"
+
+bool __read_mostly enable_sgx;
+
+static inline bool encls_leaf_enabled_in_guest(struct kvm_vcpu *vcpu, u32 leaf)
+{
+	if (!enable_sgx || !guest_cpuid_has(vcpu, X86_FEATURE_SGX))
+		return false;
+
+	if (leaf >= ECREATE && leaf <= ETRACK)
+		return guest_cpuid_has(vcpu, X86_FEATURE_SGX1);
+
+	if (leaf >= EAUG && leaf <= EMODT)
+		return guest_cpuid_has(vcpu, X86_FEATURE_SGX2);
+
+	return false;
+}
+
+static inline bool sgx_enabled_in_guest_bios(struct kvm_vcpu *vcpu)
+{
+	const u64 bits = FEAT_CTL_SGX_ENABLED | FEAT_CTL_LOCKED;
+
+	return (to_vmx(vcpu)->msr_ia32_feature_control & bits) == bits;
+}
+
+int handle_encls(struct kvm_vcpu *vcpu)
+{
+	u32 leaf = (u32)kvm_rax_read(vcpu);
+
+	if (!encls_leaf_enabled_in_guest(vcpu, leaf)) {
+		kvm_queue_exception(vcpu, UD_VECTOR);
+	} else if (!sgx_enabled_in_guest_bios(vcpu)) {
+		kvm_inject_gp(vcpu, 0);
+	} else {
+		WARN(1, "KVM: unexpected exit on ENCLS[%u]", leaf);
+		vcpu->run->exit_reason = KVM_EXIT_UNKNOWN;
+		vcpu->run->hw.hardware_exit_reason = EXIT_REASON_ENCLS;
+		return 0;
+	}
+	return 1;
+}

arch/x86/kvm/vmx/sgx.h

@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __KVM_X86_SGX_H
+#define __KVM_X86_SGX_H
+
+#include <linux/kvm_host.h>
+
+#ifdef CONFIG_X86_SGX_KVM
+extern bool __read_mostly enable_sgx;
+
+int handle_encls(struct kvm_vcpu *vcpu);
+#else
+#define enable_sgx 0
+#endif
+
+#endif /* __KVM_X86_SGX_H */

arch/x86/kvm/vmx/vmx.c

@@ -57,6 +57,7 @@
 #include "mmu.h"
 #include "nested.h"
 #include "pmu.h"
+#include "sgx.h"
 #include "trace.h"
 #include "vmcs.h"
 #include "vmcs12.h"
@@ -5607,16 +5608,18 @@ static int handle_vmx_instruction(struct kvm_vcpu *vcpu)
 	return 1;
 }
 
+#ifndef CONFIG_X86_SGX_KVM
 static int handle_encls(struct kvm_vcpu *vcpu)
 {
 	/*
-	 * SGX virtualization is not yet supported.  There is no software
+	 * SGX virtualization is disabled.  There is no software enable bit for
-	 * enable bit for SGX, so we have to trap ENCLS and inject a #UD
+	 * SGX, so KVM intercepts all ENCLS leafs and injects a #UD to prevent
-	 * to prevent the guest from executing ENCLS.
+	 * the guest from executing ENCLS (when SGX is supported by hardware).
 	 */
 	kvm_queue_exception(vcpu, UD_VECTOR);
 	return 1;
 }
+#endif /* CONFIG_X86_SGX_KVM */
 
 static int handle_bus_lock_vmexit(struct kvm_vcpu *vcpu)
 {