i386: Add FEAT_8000_0008_EBX CPUID feature word

Add the new feature word and the "ibpb" feature flag.

Based on a patch by Paolo Bonzini.
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>
Message-Id: <20180109154519.25634-5-ehabkost@redhat.com>
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>

target/i386/cpu.c

@@ -483,6 +483,22 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
         .tcg_features = TCG_APM_FEATURES,
         .unmigratable_flags = CPUID_APM_INVTSC,
     },
+    [FEAT_8000_0008_EBX] = {
+        .feat_names = {
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            "ibpb", NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+        },
+        .cpuid_eax = 0x80000008,
+        .cpuid_reg = R_EBX,
+        .tcg_features = 0,
+        .unmigratable_flags = 0,
+    },
     [FEAT_XSAVE] = {
         .feat_names = {
             "xsaveopt", "xsavec", "xgetbv1", "xsaves",
@@ -3130,7 +3146,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
         } else {
             *eax = cpu->phys_bits;
         }
-        *ebx = 0;
+        *ebx = env->features[FEAT_8000_0008_EBX];
         *ecx = 0;
         *edx = 0;
         if (cs->nr_cores * cs->nr_threads > 1) {
@@ -3593,6 +3609,7 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
         x86_cpu_adjust_feat_level(cpu, FEAT_8000_0001_EDX);
         x86_cpu_adjust_feat_level(cpu, FEAT_8000_0001_ECX);
         x86_cpu_adjust_feat_level(cpu, FEAT_8000_0007_EDX);
+        x86_cpu_adjust_feat_level(cpu, FEAT_8000_0008_EBX);
         x86_cpu_adjust_feat_level(cpu, FEAT_C000_0001_EDX);
         x86_cpu_adjust_feat_level(cpu, FEAT_SVM);
         x86_cpu_adjust_feat_level(cpu, FEAT_XSAVE);

target/i386/cpu.h

@@ -472,6 +472,7 @@ typedef enum FeatureWord {
     FEAT_8000_0001_EDX, /* CPUID[8000_0001].EDX */
     FEAT_8000_0001_ECX, /* CPUID[8000_0001].ECX */
     FEAT_8000_0007_EDX, /* CPUID[8000_0007].EDX */
+    FEAT_8000_0008_EBX, /* CPUID[8000_0008].EBX */
     FEAT_C000_0001_EDX, /* CPUID[C000_0001].EDX */
     FEAT_KVM,           /* CPUID[4000_0001].EAX (KVM_CPUID_FEATURES) */
     FEAT_HYPERV_EAX,    /* CPUID[4000_0003].EAX */
@@ -669,6 +670,8 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
 #define CPUID_7_0_EDX_AVX512_4FMAPS (1U << 3) /* AVX512 Multiply Accumulation Single Precision */
 #define CPUID_7_0_EDX_SPEC_CTRL     (1U << 26) /* Speculation Control */
 
+#define CPUID_8000_0008_EBX_IBPB    (1U << 12) /* Indirect Branch Prediction Barrier */
+
 #define CPUID_XSAVE_XSAVEOPT   (1U << 0)
 #define CPUID_XSAVE_XSAVEC     (1U << 1)
 #define CPUID_XSAVE_XGETBV1    (1U << 2)