i386/cpu: Add APX migration support

Add a VMStateDescription to migrate APX EGPRs.

Tested-by: Xudong Hao <xudong.hao@intel.com>
Signed-off-by: Zide Chen <zide.chen@intel.com>
Co-developed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20251211070942.3612547-8-zhao1.liu@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target/i386/machine.c

@@ -1741,6 +1741,28 @@ static const VMStateDescription vmstate_cet = {
     },
 };
 
+#ifdef TARGET_X86_64
+static bool apx_needed(void *opaque)
+{
+    X86CPU *cpu = opaque;
+    CPUX86State *env = &cpu->env;
+
+    return !!(env->features[FEAT_7_1_EDX] & CPUID_7_1_EDX_APXF);
+}
+
+static const VMStateDescription vmstate_apx = {
+    .name = "cpu/apx",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = apx_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINTTL_SUB_ARRAY(env.regs, X86CPU, CPU_NB_REGS,
+                                 CPU_NB_EREGS - CPU_NB_REGS),
+        VMSTATE_END_OF_LIST()
+    }
+};
+#endif
+
 const VMStateDescription vmstate_x86_cpu = {
     .name = "cpu",
     .version_id = 12,
@@ -1892,6 +1914,9 @@ const VMStateDescription vmstate_x86_cpu = {
         &vmstate_triple_fault,
         &vmstate_pl0_ssp,
         &vmstate_cet,
+#ifdef TARGET_X86_64
+        &vmstate_apx,
+#endif
         NULL
     }
 };