LoongArch: KVM: Add PTW feature detection on new hardware

With new Loongson-3A6000/3C6000 hardware platforms (or later), hardware
page table walking (PTW) feature is supported on host. So here add this
feature detection on KVM host.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>

arch/loongarch/include/uapi/asm/kvm.h

@@ -101,6 +101,7 @@ struct kvm_fpu {
 #define  KVM_LOONGARCH_VM_FEAT_PMU		5
 #define  KVM_LOONGARCH_VM_FEAT_PV_IPI		6
 #define  KVM_LOONGARCH_VM_FEAT_PV_STEALTIME	7
+#define  KVM_LOONGARCH_VM_FEAT_PTW		8
 
 /* Device Control API on vcpu fd */
 #define KVM_LOONGARCH_VCPU_CPUCFG	0

arch/loongarch/kvm/vcpu.c

@@ -645,6 +645,8 @@ static int _kvm_get_cpucfg_mask(int id, u64 *v)
 			*v |= CPUCFG2_ARMBT;
 		if (cpu_has_lbt_mips)
 			*v |= CPUCFG2_MIPSBT;
+		if (cpu_has_ptw)
+			*v |= CPUCFG2_PTW;
 
 		return 0;
 	case LOONGARCH_CPUCFG3:

arch/loongarch/kvm/vm.c

@@ -139,6 +139,10 @@ static int kvm_vm_feature_has_attr(struct kvm *kvm, struct kvm_device_attr *attr
 		if (kvm_pvtime_supported())
 			return 0;
 		return -ENXIO;
+	case KVM_LOONGARCH_VM_FEAT_PTW:
+		if (cpu_has_ptw)
+			return 0;
+		return -ENXIO;
 	default:
 		return -ENXIO;
 	}