[PATCH v2 4/4] LoongArch: KVM: Add VM LBT feature detection support

[Bibo Mao]

Before virt machine or vcpu is created, vmm need check supported
features from KVM. Here ioctl command KVM_HAS_DEVICE_ATTR is added
for VM, and macro KVM_LOONGARCH_VM_FEAT_CTRL is added to check
supported feature.

Now only KVM_LOONGARCH_VM_FEAT_LBT feature is added, in later any new
feature can be added if it is used for vmm.

Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx>
---
 arch/loongarch/include/uapi/asm/kvm.h |  4 ++++
 arch/loongarch/kvm/vm.c               | 34 ++++++++++++++++++++++++++-
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/arch/loongarch/include/uapi/asm/kvm.h b/arch/loongarch/include/uapi/asm/kvm.h
index 656aa6a723a6..8605ecc27806 100644
--- a/arch/loongarch/include/uapi/asm/kvm.h
+++ b/arch/loongarch/include/uapi/asm/kvm.h
@@ -91,6 +91,10 @@ struct kvm_fpu {
 #define KVM_IOC_CSRID(REG)		LOONGARCH_REG_64(KVM_REG_LOONGARCH_CSR, REG)
 #define KVM_IOC_CPUCFG(REG)		LOONGARCH_REG_64(KVM_REG_LOONGARCH_CPUCFG, REG)
 
+/* Device Control API on vm fd */
+#define KVM_LOONGARCH_VM_FEAT_CTRL	0
+#define  KVM_LOONGARCH_VM_FEAT_LBT	0
+
 /* Device Control API on vcpu fd */
 #define KVM_LOONGARCH_VCPU_CPUCFG	0
 #define KVM_LOONGARCH_VCPU_PVTIME_CTRL	1
diff --git a/arch/loongarch/kvm/vm.c b/arch/loongarch/kvm/vm.c
index 6b2e4f66ad26..38452bc23f8c 100644
--- a/arch/loongarch/kvm/vm.c
+++ b/arch/loongarch/kvm/vm.c
@@ -99,7 +99,39 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	return r;
 }
 
+static int kvm_vm_feature_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	switch (attr->attr) {
+	case KVM_LOONGARCH_VM_FEAT_LBT:
+		return 0;
+	default:
+		return -ENXIO;
+	}
+}
+
+static int kvm_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	switch (attr->group) {
+	case KVM_LOONGARCH_VM_FEAT_CTRL:
+		return kvm_vm_feature_has_attr(kvm, attr);
+	default:
+		return -ENXIO;
+	}
+}
+
 int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
 {
-	return -ENOIOCTLCMD;
+	struct kvm *kvm = filp->private_data;
+	void __user *argp = (void __user *)arg;
+	struct kvm_device_attr attr;
+
+	switch (ioctl) {
+	case KVM_HAS_DEVICE_ATTR:
+		if (copy_from_user(&attr, argp, sizeof(attr)))
+			return -EFAULT;
+
+		return kvm_vm_has_attr(kvm, &attr);
+	default:
+		return -EINVAL;
+	}
 }
-- 
2.39.3