[RFC PATCH v2 2/6] KVM: arm64: Add vm fd device attribute accessors

[Oliver Upton <oliver.upton@linux.dev>]

A subsequent change will allow userspace to convey a filter for
hypercalls through a vm device attribute. Add the requisite boilerplate
for vm attribute accessors.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
 arch/arm64/kvm/arm.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 9c5573bc4614..09efa893e03a 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1449,11 +1449,28 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
 	}
 }
 
+static int kvm_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	switch (attr->group) {
+	default:
+		return -ENXIO;
+	}
+}
+
+static int kvm_vm_set_attr(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	switch (attr->group) {
+	default:
+		return -ENXIO;
+	}
+}
+
 long kvm_arch_vm_ioctl(struct file *filp,
 		       unsigned int ioctl, unsigned long arg)
 {
 	struct kvm *kvm = filp->private_data;
 	void __user *argp = (void __user *)arg;
+	struct kvm_device_attr attr;
 
 	switch (ioctl) {
 	case KVM_CREATE_IRQCHIP: {
@@ -1489,6 +1506,18 @@ long kvm_arch_vm_ioctl(struct file *filp,
 			return -EFAULT;
 		return kvm_vm_ioctl_mte_copy_tags(kvm, &copy_tags);
 	}
+	case KVM_HAS_DEVICE_ATTR: {
+		if (copy_from_user(&attr, argp, sizeof(attr)))
+			return -EFAULT;
+
+		return kvm_vm_has_attr(kvm, &attr);
+	}
+	case KVM_SET_DEVICE_ATTR: {
+		if (copy_from_user(&attr, argp, sizeof(attr)))
+			return -EFAULT;
+
+		return kvm_vm_set_attr(kvm, &attr);
+	}
 	default:
 		return -EINVAL;
 	}
-- 
2.39.1.581.gbfd45094c4-goog