KVM: x86: Add reverse-CPUID lookup support for scattered SGX features

Define a new KVM-only feature word for advertising and querying SGX
sub-features in CPUID.0x12.0x0.EAX.  Because SGX1 and SGX2 are scattered
in the kernel's feature word, they need to be translated so that the
bit numbers match those of hardware.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Kai Huang <kai.huang@intel.com>
Message-Id: <e797c533f4c71ae89265bbb15a02aef86b67cbec.1618196135.git.kai.huang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/cpuid.h

@@ -13,12 +13,17 @@
  * "bug" caps, but KVM doesn't use those.
  */
 enum kvm_only_cpuid_leafs {
-	NR_KVM_CPU_CAPS = NCAPINTS,
+	CPUID_12_EAX	 = NCAPINTS,
+	NR_KVM_CPU_CAPS,
 
 	NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
 };
 
-#define X86_KVM_FEATURE(w, f)		((w)*32 + (f))
+#define KVM_X86_FEATURE(w, f)		((w)*32 + (f))
+
+/* Intel-defined SGX sub-features, CPUID level 0x12 (EAX). */
+#define KVM_X86_FEATURE_SGX1		KVM_X86_FEATURE(CPUID_12_EAX, 0)
+#define KVM_X86_FEATURE_SGX2		KVM_X86_FEATURE(CPUID_12_EAX, 1)
 
 extern u32 kvm_cpu_caps[NR_KVM_CPU_CAPS] __read_mostly;
 void kvm_set_cpu_caps(void);
@@ -93,6 +98,7 @@ static const struct cpuid_reg reverse_cpuid[] = {
 	[CPUID_8000_0007_EBX] = {0x80000007, 0, CPUID_EBX},
 	[CPUID_7_EDX]         = {         7, 0, CPUID_EDX},
 	[CPUID_7_1_EAX]       = {         7, 1, CPUID_EAX},
+	[CPUID_12_EAX]        = {0x00000012, 0, CPUID_EAX},
 };
 
 /*
@@ -119,6 +125,11 @@ static __always_inline void reverse_cpuid_check(unsigned int x86_leaf)
  */
 static __always_inline u32 __feature_translate(int x86_feature)
 {
+	if (x86_feature == X86_FEATURE_SGX1)
+		return KVM_X86_FEATURE_SGX1;
+	else if (x86_feature == X86_FEATURE_SGX2)
+		return KVM_X86_FEATURE_SGX2;
+
 	return x86_feature;
 }