CPUID leaf 12_1_EBX is an Intel-defined feature bits leaf enumerating
the platform's SGX extended capabilities.  Currently there is a single
capabilitiy:

  - EXINFO: record information about #PFs and #GPs in the enclave's SSA

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 target/i386/cpu.c | 20 ++++++++++++++++++++
 target/i386/cpu.h |  1 +
 2 files changed, 21 insertions(+)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index e3dd76d3ba..ab08c1765e 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -777,6 +777,7 @@ static void x86_cpu_vendor_words2str(char *dst, uint32_t vendor1,
           CPUID_XSAVE_XSAVEC, CPUID_XSAVE_XSAVES */
 #define TCG_SGX_12_0_EAX_FEATURES 0
 #define TCG_SGX_12_1_EAX_FEATURES 0
+#define TCG_SGX_12_1_EBX_FEATURES 0
 
 typedef enum FeatureWordType {
    CPUID_FEATURE_WORD,
@@ -1264,6 +1265,25 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
         },
         .tcg_features = TCG_SGX_12_1_EAX_FEATURES,
     },
+    [FEAT_SGX_12_1_EBX] = {
+        .type = CPUID_FEATURE_WORD,
+        .feat_names = {
+            "sgx-exinfo" , NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+        },
+        .cpuid = {
+            .eax = 0x12,
+            .needs_ecx = true, .ecx = 1,
+            .reg = R_EBX,
+        },
+        .tcg_features = TCG_SGX_12_1_EBX_FEATURES,
+    },
 };
 
 typedef struct X86RegisterInfo32 {
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index fe4660effa..4139c94669 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -508,6 +508,7 @@ typedef enum FeatureWord {
     FEAT_CORE_CAPABILITY,
     FEAT_SGX_12_0_EAX,  /* CPUID[EAX=0x12,ECX=0].EAX (SGX) */
     FEAT_SGX_12_1_EAX,  /* CPUID[EAX=0x12,ECX=1].EAX (SGX ATTRIBUTES[31:0]) */
+    FEAT_SGX_12_1_EBX,  /* CPUID[EAX=0x12,ECX=1].EBX (SGX MISCSELECT[31:0]) */
     FEATURE_WORDS,
 } FeatureWord;
 
-- 
2.22.0