target/loongarch: Add kvm steal time feature detection

Paravirt steal time feature is OnOffAuto type, feature detection is added
to check whether it is supported on KVM host.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Reviewed-by: Bibo Mao <maobibo@loongson.cn>

target/loongarch/cpu.h

@@ -288,6 +288,7 @@ enum loongarch_features {
     LOONGARCH_FEATURE_LBT, /* loongson binary translation extension */
     LOONGARCH_FEATURE_PMU,
     LOONGARCH_FEATURE_PV_IPI,
+    LOONGARCH_FEATURE_STEALTIME,
 };
 
 typedef struct  LoongArchBT {

target/loongarch/kvm/kvm.c

@@ -924,6 +924,12 @@ static bool kvm_feature_supported(CPUState *cs, enum loongarch_features feature)
         ret = kvm_vm_ioctl(kvm_state, KVM_HAS_DEVICE_ATTR, &attr);
         return (ret == 0);
 
+    case LOONGARCH_FEATURE_STEALTIME:
+        attr.group = KVM_LOONGARCH_VM_FEAT_CTRL;
+        attr.attr = KVM_LOONGARCH_VM_FEAT_PV_STEALTIME;
+        ret = kvm_vm_ioctl(kvm_state, KVM_HAS_DEVICE_ATTR, &attr);
+        return (ret == 0);
+
     default:
         return false;
     }
@@ -1042,6 +1048,20 @@ static int kvm_cpu_check_pv_features(CPUState *cs, Error **errp)
         env->pv_features |= BIT(KVM_FEATURE_IPI);
     }
 
+    kvm_supported = kvm_feature_supported(cs, LOONGARCH_FEATURE_STEALTIME);
+    if (cpu->kvm_steal_time == ON_OFF_AUTO_ON) {
+        if (!kvm_supported) {
+            error_setg(errp, "'kvm stealtime' feature not supported by KVM host");
+            return -ENOTSUP;
+        }
+    } else if (cpu->kvm_steal_time != ON_OFF_AUTO_AUTO) {
+        kvm_supported = false;
+    }
+
+    if (kvm_supported) {
+        env->pv_features |= BIT(KVM_FEATURE_STEAL_TIME);
+    }
+
     return 0;
 }