vfio: ABI for mdev display dma-buf operation

Add VFIO_DEVICE_QUERY_GFX_PLANE ioctl command to let user query and get
a plane and its information. So far, two types of buffers are supported:
buffers based on dma-buf and buffers based on region.

This ioctl can be invoked with:
1) Either DMABUF or REGION flag. Vendor driver returns a plane_info
successfully only when the specific kind of buffer is supported.
2) Flag PROBE. And at the same time either DMABUF or REGION must be set,
so that vendor driver returns success only when the specific kind of
buffer is supported.

Add VFIO_DEVICE_GET_GFX_DMABUF ioctl command to let user get a specific
dma-buf fd of an exposed MDEV buffer provided by dmabuf_id which was
returned in VFIO_DEVICE_QUERY_GFX_PLANE ioctl command.

The life cycle of an exposed MDEV buffer is handled by userspace and
tracked by kernel space. The returned dmabuf_id in struct vfio_device_
query_gfx_plane can be a new id of a new exposed buffer or an old id of
a re-exported buffer. Host user can check the value of dmabuf_id to see
if it needs to create new resources according to the new exposed buffer
or just re-use the existing resource related to the old buffer.

v18:
- update comments for VFIO_DEVICE_GET_GFX_DMABUF. (Alex)

v17:
- modify VFIO_DEVICE_GET_GFX_DMABUF interface. (Alex)

v16:
- add x_hot and y_hot fields. (Gerd)
- add comments for VFIO_DEVICE_GET_GFX_DMABUF. (Alex)
- rebase to 4.14.0-rc6.

v15:
- add a ioctl to get a dmabuf for a given dmabuf id. (Gerd)

v14:
- add PROBE, DMABUF and REGION flags. (Alex)

v12:
- add drm_format_mod back. (Gerd and Zhenyu)
- add region_index. (Gerd)

v11:
- rename plane_type to drm_plane_type. (Gerd)
- move fields of vfio_device_query_gfx_plane to vfio_device_gfx_plane_info.
  (Gerd)
- remove drm_format_mod, start fields. (Daniel)
- remove plane_id.

v10:
- refine the ABI API VFIO_DEVICE_QUERY_GFX_PLANE. (Alex) (Gerd)

v3:
- add a field gvt_plane_info in the drm_i915_gem_obj structure to save
  the decoded plane information to avoid look up while need the plane
  info. (Gerd)
Signed-off-by: Tina Zhang <tina.zhang@intel.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Kirti Wankhede <kwankhede@nvidia.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

include/uapi/linux/vfio.h

@@ -502,6 +502,68 @@ struct vfio_pci_hot_reset {
 
 #define VFIO_DEVICE_PCI_HOT_RESET	_IO(VFIO_TYPE, VFIO_BASE + 13)
 
+/**
+ * VFIO_DEVICE_QUERY_GFX_PLANE - _IOW(VFIO_TYPE, VFIO_BASE + 14,
+ *                                    struct vfio_device_query_gfx_plane)
+ *
+ * Set the drm_plane_type and flags, then retrieve the gfx plane info.
+ *
+ * flags supported:
+ * - VFIO_GFX_PLANE_TYPE_PROBE and VFIO_GFX_PLANE_TYPE_DMABUF are set
+ *   to ask if the mdev supports dma-buf. 0 on support, -EINVAL on no
+ *   support for dma-buf.
+ * - VFIO_GFX_PLANE_TYPE_PROBE and VFIO_GFX_PLANE_TYPE_REGION are set
+ *   to ask if the mdev supports region. 0 on support, -EINVAL on no
+ *   support for region.
+ * - VFIO_GFX_PLANE_TYPE_DMABUF or VFIO_GFX_PLANE_TYPE_REGION is set
+ *   with each call to query the plane info.
+ * - Others are invalid and return -EINVAL.
+ *
+ * Note:
+ * 1. Plane could be disabled by guest. In that case, success will be
+ *    returned with zero-initialized drm_format, size, width and height
+ *    fields.
+ * 2. x_hot/y_hot is set to 0xFFFFFFFF if no hotspot information available
+ *
+ * Return: 0 on success, -errno on other failure.
+ */
+struct vfio_device_gfx_plane_info {
+	__u32 argsz;
+	__u32 flags;
+#define VFIO_GFX_PLANE_TYPE_PROBE (1 << 0)
+#define VFIO_GFX_PLANE_TYPE_DMABUF (1 << 1)
+#define VFIO_GFX_PLANE_TYPE_REGION (1 << 2)
+	/* in */
+	__u32 drm_plane_type;	/* type of plane: DRM_PLANE_TYPE_* */
+	/* out */
+	__u32 drm_format;	/* drm format of plane */
+	__u64 drm_format_mod;   /* tiled mode */
+	__u32 width;	/* width of plane */
+	__u32 height;	/* height of plane */
+	__u32 stride;	/* stride of plane */
+	__u32 size;	/* size of plane in bytes, align on page*/
+	__u32 x_pos;	/* horizontal position of cursor plane */
+	__u32 y_pos;	/* vertical position of cursor plane*/
+	__u32 x_hot;    /* horizontal position of cursor hotspot */
+	__u32 y_hot;    /* vertical position of cursor hotspot */
+	union {
+		__u32 region_index;	/* region index */
+		__u32 dmabuf_id;	/* dma-buf id */
+	};
+};
+
+#define VFIO_DEVICE_QUERY_GFX_PLANE _IO(VFIO_TYPE, VFIO_BASE + 14)
+
+/**
+ * VFIO_DEVICE_GET_GFX_DMABUF - _IOW(VFIO_TYPE, VFIO_BASE + 15, __u32)
+ *
+ * Return a new dma-buf file descriptor for an exposed guest framebuffer
+ * described by the provided dmabuf_id. The dmabuf_id is returned from VFIO_
+ * DEVICE_QUERY_GFX_PLANE as a token of the exposed guest framebuffer.
+ */
+
+#define VFIO_DEVICE_GET_GFX_DMABUF _IO(VFIO_TYPE, VFIO_BASE + 15)
+
 /* -------- API for Type1 VFIO IOMMU -------- */
 
 /**