[Linaro-mm-sig] Re: [PATCH v2 4/4] vfio/pci: Allow MMIO regions to be exported through dma-buf

+{

• struct vfio_pci_dma_buf *priv = dmabuf->priv;
• int rc;
• rc = pci_p2pdma_distance_many(priv->vdev->pdev, &attachment->dev, 1,

• 		      true);
  

This should just use pci_p2pdma_distance.

• /*

• * Since the memory being mapped is a device memory it could never be in
  

• * CPU caches.
  

• */
  

DMA_ATTR_SKIP_CPU_SYNC doesn't even apply to dma_map_resource, not sure where this wisdom comes from.

• dma_addr = dma_map_resource(

• attachment->dev,
  

• pci_resource_start(priv->vdev->pdev, priv->index) +
  

• 	priv->offset,
  

• priv->dmabuf->size, dir, DMA_ATTR_SKIP_CPU_SYNC);
  

This is not how P2P addresses are mapped. You need to use dma_map_sgtable and have the proper pgmap for it.

The above is just a badly implemented version of the dma-direct PCI_P2PDMA_MAP_BUS_ADDR case, ignoring mappings through the host bridge or dma-map-ops interactions.