On Thu, Sep 16, 2021 at 05:40:48PM -0600, Logan Gunthorpe wrote: > When a PCI P2PDMA page is seen, set the IOVA length of the segment > to zero so that it is not mapped into the IOVA. Then, in finalise_sg(), > apply the appropriate bus address to the segment. The IOVA is not > created if the scatterlist only consists of P2PDMA pages. > > A P2PDMA page may have three possible outcomes when being mapped: > 1) If the data path between the two devices doesn't go through > the root port, then it should be mapped with a PCI bus address > 2) If the data path goes through the host bridge, it should be mapped > normally with an IOMMU IOVA. > 3) It is not possible for the two devices to communicate and thus > the mapping operation should fail (and it will return -EREMOTEIO). > > Similar to dma-direct, the sg_dma_mark_pci_p2pdma() flag is used to > indicate bus address segments. On unmap, P2PDMA segments are skipped > over when determining the start and end IOVA addresses. > > With this change, the flags variable in the dma_map_ops is set to > DMA_F_PCI_P2PDMA_SUPPORTED to indicate support for P2PDMA pages. > > Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx> > --- > drivers/iommu/dma-iommu.c | 68 +++++++++++++++++++++++++++++++++++---- > 1 file changed, 61 insertions(+), 7 deletions(-) Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Jason
