[v2,2/2] target/i386: Add support for save/load IA32_UMWAIT_CONTROL MSR

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 66fa61f02b..9d1c8edc1f 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -459,6 +459,7 @@  typedef enum X86Seg {
 
 #define MSR_IA32_BNDCFGS                0x00000d90
 #define MSR_IA32_XSS                    0x00000da0
+#define MSR_IA32_UMWAIT_CONTROL         0xe1
 
 #define XSTATE_FP_BIT                   0
 #define XSTATE_SSE_BIT                  1
@@ -1360,6 +1361,7 @@  typedef struct CPUX86State {
     uint16_t fpregs_format_vmstate;
 
     uint64_t xss;
+    uint64_t umwait;
 
     TPRAccess tpr_access_type;
 } CPUX86State;
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index b58fc7ab3a..7845f684fc 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -92,6 +92,7 @@  static bool has_msr_hv_stimer;
 static bool has_msr_hv_frequencies;
 static bool has_msr_hv_reenlightenment;
 static bool has_msr_xss;
+static bool has_msr_umwait;
 static bool has_msr_spec_ctrl;
 static bool has_msr_virt_ssbd;
 static bool has_msr_smi_count;
@@ -1487,6 +1488,9 @@  static int kvm_get_supported_msrs(KVMState *s)
                 case MSR_IA32_XSS:
                     has_msr_xss = true;
                     break;
+                case MSR_IA32_UMWAIT_CONTROL:
+                    has_msr_umwait = true;
+                    break;
                 case HV_X64_MSR_CRASH_CTL:
                     has_msr_hv_crash = true;
                     break;
@@ -1667,6 +1671,8 @@  int kvm_arch_init(MachineState *ms, KVMState *s)
                              strerror(-ret));
             }
         }
+    } else {
+        has_msr_umwait = false;
     }
 
     return 0;
@@ -2033,6 +2039,9 @@  static int kvm_put_msrs(X86CPU *cpu, int level)
     if (has_msr_xss) {
         kvm_msr_entry_add(cpu, MSR_IA32_XSS, env->xss);
     }
+    if (has_msr_umwait) {
+        kvm_msr_entry_add(cpu, MSR_IA32_UMWAIT_CONTROL, env->umwait);
+    }
     if (has_msr_spec_ctrl) {
         kvm_msr_entry_add(cpu, MSR_IA32_SPEC_CTRL, env->spec_ctrl);
     }
@@ -2426,6 +2435,9 @@  static int kvm_get_msrs(X86CPU *cpu)
     if (has_msr_xss) {
         kvm_msr_entry_add(cpu, MSR_IA32_XSS, 0);
     }
+    if (has_msr_umwait) {
+        kvm_msr_entry_add(cpu, MSR_IA32_UMWAIT_CONTROL, 0);
+    }
     if (has_msr_spec_ctrl) {
         kvm_msr_entry_add(cpu, MSR_IA32_SPEC_CTRL, 0);
     }
@@ -2675,6 +2687,9 @@  static int kvm_get_msrs(X86CPU *cpu)
         case MSR_IA32_XSS:
             env->xss = msrs[i].data;
             break;
+        case MSR_IA32_UMWAIT_CONTROL:
+            env->umwait = msrs[i].data;
+            break;
         default:
             if (msrs[i].index >= MSR_MC0_CTL &&
                 msrs[i].index < MSR_MC0_CTL + (env->mcg_cap & 0xff) * 4) {
diff --git a/target/i386/machine.c b/target/i386/machine.c
index 225b5d433b..e51285a583 100644
--- a/target/i386/machine.c
+++ b/target/i386/machine.c
@@ -810,6 +810,25 @@  static const VMStateDescription vmstate_xss = {
     }
 };
 
+static bool umwait_needed(void *opaque)
+{
+    X86CPU *cpu = opaque;
+    CPUX86State *env = &cpu->env;
+
+    return env->umwait != 0;
+}
+
+static const VMStateDescription vmstate_umwait = {
+    .name = "cpu/umwait",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = umwait_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT64(env.umwait, X86CPU),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 #ifdef TARGET_X86_64
 static bool pkru_needed(void *opaque)
 {
@@ -1079,6 +1098,7 @@  VMStateDescription vmstate_x86_cpu = {
         &vmstate_msr_hyperv_reenlightenment,
         &vmstate_avx512,
         &vmstate_xss,
+        &vmstate_umwait,
         &vmstate_tsc_khz,
         &vmstate_msr_smi_count,
 #ifdef TARGET_X86_64