kvm: add stubs for arch specific debugfs support

Two stubs are added:

 o kvm_arch_has_vcpu_debugfs(): must return true if the arch
   supports creating debugfs entries in the vcpu debugfs dir
   (which will be implemented by the next commit)

 o kvm_arch_create_vcpu_debugfs(): code that creates debugfs
   entries in the vcpu debugfs dir

For x86, this commit introduces a new file to avoid growing
arch/x86/kvm/x86.c even more.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/arm/kvm/arm.c

@@ -144,6 +144,16 @@ out_fail_alloc:
 	return ret;
 }
 
+bool kvm_arch_has_vcpu_debugfs(void)
+{
+	return false;
+}
+
+int kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu)
+{
+	return 0;
+}
+
 int kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf)
 {
 	return VM_FAULT_SIGBUS;

arch/mips/kvm/mips.c

@@ -140,6 +140,16 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	return 0;
 }
 
+bool kvm_arch_has_vcpu_debugfs(void)
+{
+	return false;
+}
+
+int kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu)
+{
+	return 0;
+}
+
 void kvm_mips_free_vcpus(struct kvm *kvm)
 {
 	unsigned int i;

arch/powerpc/kvm/powerpc.c

@@ -438,6 +438,16 @@ err_out:
 	return -EINVAL;
 }
 
+bool kvm_arch_has_vcpu_debugfs(void)
+{
+	return false;
+}
+
+int kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu)
+{
+	return 0;
+}
+
 void kvm_arch_destroy_vm(struct kvm *kvm)
 {
 	unsigned int i;

arch/s390/kvm/kvm-s390.c

@@ -1489,6 +1489,16 @@ out_err:
 	return rc;
 }
 
+bool kvm_arch_has_vcpu_debugfs(void)
+{
+	return false;
+}
+
+int kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu)
+{
+	return 0;
+}
+
 void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
 {
 	VCPU_EVENT(vcpu, 3, "%s", "free cpu");

arch/x86/kvm/Makefile

@@ -13,7 +13,7 @@ kvm-$(CONFIG_KVM_ASYNC_PF)	+= $(KVM)/async_pf.o
 
 kvm-y			+= x86.o mmu.o emulate.o i8259.o irq.o lapic.o \
 			   i8254.o ioapic.o irq_comm.o cpuid.o pmu.o mtrr.o \
-			   hyperv.o page_track.o
+			   hyperv.o page_track.o debugfs.o
 
 kvm-$(CONFIG_KVM_DEVICE_ASSIGNMENT)	+= assigned-dev.o iommu.o
 

arch/x86/kvm/debugfs.c

@@ -0,0 +1,20 @@
+/*
+ * Kernel-based Virtual Machine driver for Linux
+ *
+ * Copyright 2016 Red Hat, Inc. and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+#include <linux/kvm_host.h>
+
+bool kvm_arch_has_vcpu_debugfs(void)
+{
+	return false;
+}
+
+int kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu)
+{
+	return 0;
+}

include/linux/kvm_host.h

@@ -749,6 +749,9 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu);
 
+bool kvm_arch_has_vcpu_debugfs(void);
+int kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu);
+
 int kvm_arch_hardware_enable(void);
 void kvm_arch_hardware_disable(void);
 int kvm_arch_hardware_setup(void);