On 2020/2/4 下午4:21, Zhu Lingshan wrote:

quoted

+static const struct dma_map_ops vdpasim_dma_ops = {
+    .map_page = vdpasim_map_page,
+    .unmap_page = vdpasim_unmap_page,
+    .alloc = vdpasim_alloc_coherent,
+    .free = vdpasim_free_coherent,
+};
+

Hey Jason,

IMHO, it would be nice if dma_ops of the parent device could be 
re-used. vdpa_device is expecting to represent a physical device 
except this simulator, however, there are not enough information in 
vdpa_device.dev to indicating which kind physical device it attached 
to. Namely get_arch_dma_ops(struct bus type) can not work on 
vdpa_device.dev. Then it seems device drivers need to implement a wrap 
of dma_ops of parent devices. Can this work be done in the vdpa 
framework since it looks like a common task? Can 
"vd_dev->vdev.dev.parent = vdpa->dev->parent;" in virtio_vdpa_probe() 
do the work?

Thanks,
BR
Zhu Lingshan 

Good catch.

I think we can.

Thanks