[PATCH 3/4] vfio: Add external user check extension interface

[Alex Williamson <alex.williamson@redhat.com>]

This lets us check extensions, particularly VFIO_DMA_CC_IOMMU using
the external user interface, allowing KVM to probe IOMMU coherency.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/vfio.c  |    6 ++++++
 include/linux/vfio.h |    2 ++
 2 files changed, 8 insertions(+)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 21271d8..512f479 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1413,6 +1413,12 @@ int vfio_external_user_iommu_id(struct vfio_group *group)
 }
 EXPORT_SYMBOL_GPL(vfio_external_user_iommu_id);
 
+long vfio_external_check_extension(struct vfio_group *group, unsigned long arg)
+{
+	return vfio_ioctl_check_extension(group->container, arg);
+}
+EXPORT_SYMBOL_GPL(vfio_external_check_extension);
+
 /**
  * Module/class support
  */
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 24579a0..81022a52 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -96,5 +96,7 @@ extern void vfio_unregister_iommu_driver(
 extern struct vfio_group *vfio_group_get_external_user(struct file *filep);
 extern void vfio_group_put_external_user(struct vfio_group *group);
 extern int vfio_external_user_iommu_id(struct vfio_group *group);
+extern long vfio_external_check_extension(struct vfio_group *group,
+					  unsigned long arg);
 
 #endif /* VFIO_H */