[PATCH v1 05/14] vfio: Create a vfio_device from vma lookup

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

Creating an address space mapping onto our vfio pseudo fs for each
device file descriptor means that we can universally retrieve a
vfio_device from a vma mapping this file.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/vfio.c  |   19 +++++++++++++++++--
 include/linux/vfio.h |    1 +
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 3852e57b9e04..3a3e85a0dc3e 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -927,6 +927,23 @@ struct vfio_device *vfio_device_get_from_dev(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(vfio_device_get_from_dev);
 
+static const struct file_operations vfio_device_fops;
+
+struct vfio_device *vfio_device_get_from_vma(struct vm_area_struct *vma)
+{
+	struct vfio_device *device;
+
+	if (!vma->vm_file || vma->vm_file->f_op != &vfio_device_fops)
+		return ERR_PTR(-ENODEV);
+
+	device = vma->vm_file->private_data;
+
+	vfio_device_get(device);
+
+	return device;
+}
+EXPORT_SYMBOL_GPL(vfio_device_get_from_vma);
+
 static struct vfio_device *vfio_device_get_from_name(struct vfio_group *group,
 						     char *buf)
 {
@@ -1486,8 +1503,6 @@ static int vfio_group_add_container_user(struct vfio_group *group)
 	return 0;
 }
 
-static const struct file_operations vfio_device_fops;
-
 static int vfio_group_get_device_fd(struct vfio_group *group, char *buf)
 {
 	struct vfio_device *device;
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index f435dfca15eb..660b8adf90a6 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -58,6 +58,7 @@ extern void vfio_device_put(struct vfio_device *device);
 extern void *vfio_device_data(struct vfio_device *device);
 extern void vfio_device_unmap_mapping_range(struct vfio_device *device,
 					    loff_t start, loff_t len);
+extern struct vfio_device *vfio_device_get_from_vma(struct vm_area_struct *vma);
 
 /* events for the backend driver notify callback */
 enum vfio_iommu_notify_type {