In addition to memfd, a blob resource can also have its backing
storage in a VFIO device region. Since, there is no effective way
to determine where the backing storage is located, we first try to
create a dmabuf assuming it is in memfd. If that fails, we try to
create a dmabuf assuming it is in VFIO device region.

So, we first call virtio_gpu_create_udmabuf() to check if the blob's
backing storage is located in a memfd or not. If it is not, we invoke
the vfio_device_create_dmabuf_fd() API which identifies the right
VFIO device and eventually creates a dmabuf fd.

Note that, for mmapping the dmabuf, we directly call mmap() if the
dmabuf fd was created via virtio_gpu_create_udmabuf() since we know
that the udmabuf driver supports mmap(). However, if the dmabuf was
created via vfio_device_create_dmabuf_fd(), we use the
vfio_device_mmap_dmabuf() API to get a mapping for the dmabuf.

Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Alex Bennée <alex.bennee@linaro.org>
Cc: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Cc: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Cc: Alex Williamson <alex@shazbot.org>
Cc: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
---
 hw/display/virtio-gpu-dmabuf.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/hw/display/virtio-gpu-dmabuf.c b/hw/display/virtio-gpu-dmabuf.c
index 0a6b54fde5..55e3f60b60 100644
--- a/hw/display/virtio-gpu-dmabuf.c
+++ b/hw/display/virtio-gpu-dmabuf.c
@@ -148,9 +148,22 @@ void virtio_gpu_init_dmabuf(struct virtio_gpu_simple_resource *res)
         if (res->dmabuf_fd == VFIO_DMABUF_CREATE_ERR_INVALID_IOV) {
             error_free_or_abort(&local_err);
 
-            qemu_log_mask(LOG_GUEST_ERROR,
-                          "Cannot create dmabuf: incompatible memory\n");
-            return;
+            res->dmabuf_fd = vfio_device_create_dmabuf_fd(res->iov,
+                                                          res->iov_cnt,
+                                                          &local_err);
+            if (res->dmabuf_fd == VFIO_DMABUF_CREATE_ERR_INVALID_IOV) {
+                error_free_or_abort(&local_err);
+                qemu_log_mask(LOG_GUEST_ERROR,
+                              "Cannot create dmabuf: incompatible memory\n");
+                return;
+            }
+
+            if (res->dmabuf_fd < 0 ||
+                !vfio_device_mmap_dmabuf(res->iov, res->iov_cnt, &pdata,
+                                         res->blob_size, &local_err)) {
+                virtio_gpu_destroy_dmabuf(res);
+                res->dmabuf_fd = -1;
+            }
         } else if (res->dmabuf_fd < 0 ||
                    !virtio_gpu_remap_dmabuf(res, &pdata, &local_err)) {
             virtio_gpu_destroy_dmabuf(res);
-- 
2.53.0