target-i386: Introduce generic CPUID feature compat function

Introduce x86_cpu_compat_set_features(), that can be used to set/unset
feature bits on specific CPU models for machine-type compatibility.
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>
Signed-off-by: NAndreas Färber <afaerber@suse.de>

target-i386/cpu.c

@@ -971,6 +971,32 @@ static x86_def_t builtin_x86_defs[] = {
     },
 };
 
+/**
+ * x86_cpu_compat_set_features:
+ * @cpu_model: CPU model name to be changed. If NULL, all CPU models are changed
+ * @w: Identifies the feature word to be changed.
+ * @feat_add: Feature bits to be added to feature word
+ * @feat_remove: Feature bits to be removed from feature word
+ *
+ * Change CPU model feature bits for compatibility.
+ *
+ * This function may be used by machine-type compatibility functions
+ * to enable or disable feature bits on specific CPU models.
+ */
+void x86_cpu_compat_set_features(const char *cpu_model, FeatureWord w,
+                                 uint32_t feat_add, uint32_t feat_remove)
+{
+    x86_def_t *def;
+    int i;
+    for (i = 0; i < ARRAY_SIZE(builtin_x86_defs); i++) {
+        def = &builtin_x86_defs[i];
+        if (!cpu_model || !strcmp(cpu_model, def->name)) {
+            def->features[w] |= feat_add;
+            def->features[w] &= ~feat_remove;
+        }
+    }
+}
+
 #ifdef CONFIG_KVM
 static int cpu_x86_fill_model_id(char *str)
 {

target-i386/cpu.h

@@ -1255,6 +1255,10 @@ void cpu_report_tpr_access(CPUX86State *env, TPRAccess access);
 
 void disable_kvm_pv_eoi(void);
 
+void x86_cpu_compat_set_features(const char *cpu_model, FeatureWord w,
+                                 uint32_t feat_add, uint32_t feat_remove);
+
+
 /* Return name of 32-bit register, from a R_* constant */
 const char *get_register_name_32(unsigned int reg);