kvm: Add support for arch compat vm ioctls

We will introduce the first architecture specific compat vm ioctl in the
next patch. Add all necessary boilerplate to allow architectures to
override compat vm ioctls when necessary.

Signed-off-by: Alexander Graf <graf@amazon.com>
Message-Id: <20221017184541.2658-2-graf@amazon.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/linux/kvm_host.h

@@ -1390,6 +1390,8 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 			    struct kvm_enable_cap *cap);
 long kvm_arch_vm_ioctl(struct file *filp,
 		       unsigned int ioctl, unsigned long arg);
+long kvm_arch_vm_compat_ioctl(struct file *filp, unsigned int ioctl,
+			      unsigned long arg);
 
 int kvm_arch_vcpu_ioctl_get_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu);
 int kvm_arch_vcpu_ioctl_set_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu);

virt/kvm/kvm_main.c

@@ -4839,6 +4839,12 @@ struct compat_kvm_clear_dirty_log {
 	};
 };
 
+long __weak kvm_arch_vm_compat_ioctl(struct file *filp, unsigned int ioctl,
+				     unsigned long arg)
+{
+	return -ENOTTY;
+}
+
 static long kvm_vm_compat_ioctl(struct file *filp,
 			   unsigned int ioctl, unsigned long arg)
 {
@@ -4847,6 +4853,11 @@ static long kvm_vm_compat_ioctl(struct file *filp,
 
 	if (kvm->mm != current->mm || kvm->vm_dead)
 		return -EIO;
+
+	r = kvm_arch_vm_compat_ioctl(filp, ioctl, arg);
+	if (r != -ENOTTY)
+		return r;
+
 	switch (ioctl) {
 #ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
 	case KVM_CLEAR_DIRTY_LOG: {