[RFC 12/12] vfio: Compile group optionally

[Yi Liu <yi.l.liu@intel.com>]

group code is not needed for vfio device cdev, so with vfio device cdev
introduced, the group infrastructures can be compiled out.

Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
 drivers/vfio/Kconfig  | 17 +++++++++++
 drivers/vfio/Makefile |  3 +-
 drivers/vfio/vfio.h   | 69 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/vfio.h  | 11 +++++++
 4 files changed, 99 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
index 286c1663bd75..49bcc198d386 100644
--- a/drivers/vfio/Kconfig
+++ b/drivers/vfio/Kconfig
@@ -12,9 +12,26 @@ menuconfig VFIO
 	  If you don't know what to do here, say N.
 
 if VFIO
+config VFIO_ENABLE_GROUP
+	bool
+	default !IOMMUFD
+
+config VFIO_GROUP
+	bool "Support for the VFIO group /dev/vfio/$group_id"
+	select VFIO_ENABLE_GROUP
+	default y
+	help
+	   VFIO group is legacy interface for userspace. For userspaces
+	   adapted to iommufd and vfio device cdev, this can be N. For
+	   now, before iommufd is ready and userspace applications fully
+	   converted to iommufd and vfio device cdev, this should be Y.
+
+	   If you don't know what to do here, say Y.
+
 config VFIO_CONTAINER
 	bool "Support for the VFIO container /dev/vfio/vfio"
 	select VFIO_IOMMU_TYPE1 if MMU && (X86 || S390 || ARM || ARM64)
+	depends on VFIO_ENABLE_GROUP
 	default y
 	help
 	  The VFIO container is the classic interface to VFIO for establishing
diff --git a/drivers/vfio/Makefile b/drivers/vfio/Makefile
index 3783db7e8082..7f47d508d866 100644
--- a/drivers/vfio/Makefile
+++ b/drivers/vfio/Makefile
@@ -4,8 +4,9 @@ vfio_virqfd-y := virqfd.o
 obj-$(CONFIG_VFIO) += vfio.o
 
 vfio-y += vfio_main.o \
-	  group.o \
 	  iova_bitmap.o
+
+vfio-$(CONFIG_VFIO_ENABLE_GROUP) += group.o
 vfio-$(CONFIG_IOMMUFD) += iommufd.o
 vfio-$(CONFIG_VFIO_CONTAINER) += container.o
 
diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
index 058d7a19dada..313b0e0af846 100644
--- a/drivers/vfio/vfio.h
+++ b/drivers/vfio/vfio.h
@@ -62,6 +62,7 @@ enum vfio_group_type {
 	VFIO_NO_IOMMU,
 };
 
+#if IS_ENABLED(CONFIG_VFIO_ENABLE_GROUP)
 struct vfio_group {
 	struct device 			dev;
 	struct cdev			cdev;
@@ -104,6 +105,74 @@ bool vfio_group_has_dev(struct vfio_group *group, struct vfio_device *device);
 bool vfio_device_has_container(struct vfio_device *device);
 int __init vfio_group_init(void);
 void vfio_group_cleanup(void);
+#else
+struct vfio_group;
+
+static inline int vfio_device_set_group(struct vfio_device *device,
+					enum vfio_group_type type)
+{
+	return 0;
+}
+
+static inline void vfio_device_remove_group(struct vfio_device *device)
+{
+}
+
+static inline void vfio_device_group_register(struct vfio_device *device)
+{
+}
+
+static inline void vfio_device_group_unregister(struct vfio_device *device)
+{
+}
+
+static inline int vfio_device_group_use_iommu(struct vfio_device *device)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline void vfio_device_group_unuse_iommu(struct vfio_device *device)
+{
+}
+
+static inline void vfio_device_group_close(struct vfio_device_file *df)
+{
+}
+
+static inline struct vfio_group *vfio_group_from_file(struct file *file)
+{
+	return NULL;
+}
+
+static inline bool vfio_group_enforced_coherent(struct vfio_group *group)
+{
+	return true;
+}
+
+static inline void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm)
+{
+}
+
+static inline bool vfio_group_has_dev(struct vfio_group *group,
+				      struct vfio_device *device)
+{
+	return false;
+}
+
+static inline bool vfio_device_has_container(struct vfio_device *device)
+{
+	return false;
+}
+
+static inline int __init vfio_group_init(void)
+{
+	return 0;
+}
+
+static inline void vfio_group_cleanup(void)
+{
+}
+#endif /* CONFIG_VFIO_ENABLE_GROUP */
 
 #if IS_ENABLED(CONFIG_VFIO_CONTAINER)
 /* events for the backend driver notify callback */
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index bf909ee51185..4fd136cbf8db 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -43,7 +43,9 @@ struct vfio_device {
 	 */
 	const struct vfio_migration_ops *mig_ops;
 	const struct vfio_log_ops *log_ops;
+#if IS_ENABLED(CONFIG_VFIO_ENABLE_GROUP)
 	struct vfio_group *group;
+#endif
 	struct vfio_device_set *dev_set;
 	struct list_head dev_set_list;
 	unsigned int migration_flags;
@@ -60,8 +62,10 @@ struct vfio_device {
 	refcount_t refcount;	/* user count on registered device*/
 	unsigned int open_count;
 	struct completion comp;
+#if IS_ENABLED(CONFIG_VFIO_ENABLE_GROUP)
 	struct list_head group_next;
 	struct list_head iommu_entry;
+#endif
 	struct iommufd_access *iommufd_access;
 #if IS_ENABLED(CONFIG_IOMMUFD)
 	struct iommufd_device *iommufd_device;
@@ -244,7 +248,14 @@ int vfio_mig_get_next_state(struct vfio_device *device,
 /*
  * External user API
  */
+#if IS_ENABLED(CONFIG_VFIO_ENABLE_GROUP)
 struct iommu_group *vfio_file_iommu_group(struct file *file);
+#else
+static inline struct iommu_group *vfio_file_iommu_group(struct file *file)
+{
+	return NULL;
+}
+#endif
 bool vfio_file_is_valid(struct file *file);
 bool vfio_file_enforced_coherent(struct file *file);
 void vfio_file_set_kvm(struct file *file, struct kvm *kvm);
-- 
2.34.1