On Thu, Nov 05, 2020 at 08:42:03AM +0100, Christoph Hellwig wrote:
> Now that all users of dma_virt_ops are gone we can remove the workaround
> for it in the PCI peer to peer code.
> 
> Signed-off-by: Christoph Hellwig <h...@lst.de>
> Reviewed-by: Logan Gunthorpe <log...@deltatee.com>
> Acked-by: Bjorn Helgaas <bhelg...@google.com>
>  drivers/pci/p2pdma.c | 20 --------------------
>  1 file changed, 20 deletions(-)
> 
> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> index de1c331dbed43f..b07018af53876c 100644
> +++ b/drivers/pci/p2pdma.c
> @@ -556,15 +556,6 @@ int pci_p2pdma_distance_many(struct pci_dev *provider, 
> struct device **clients,
>               return -1;
>  
>       for (i = 0; i < num_clients; i++) {
> -#ifdef CONFIG_DMA_VIRT_OPS
> -             if (clients[i]->dma_ops == &dma_virt_ops) {
> -                     if (verbose)
> -                             dev_warn(clients[i],
> -                                      "cannot be used for peer-to-peer DMA 
> because the driver makes use of dma_virt_ops\n");
> -                     return -1;
> -             }
> -#endif
> -
>               pci_client = find_parent_pci_dev(clients[i]);
>               if (!pci_client) {
>                       if (verbose)
> @@ -837,17 +828,6 @@ static int __pci_p2pdma_map_sg(struct pci_p2pdma_pagemap 
> *p2p_pgmap,
>       phys_addr_t paddr;
>       int i;
>  
> -     /*
> -      * p2pdma mappings are not compatible with devices that use
> -      * dma_virt_ops. If the upper layers do the right thing
> -      * this should never happen because it will be prevented
> -      * by the check in pci_p2pdma_distance_many()
> -      */
> -#ifdef CONFIG_DMA_VIRT_OPS
> -     if (WARN_ON_ONCE(dev->dma_ops == &dma_virt_ops))
> -             return 0;
> -#endif

The check is removed here, but I didn't see a matching check added to
the IB side? Something like:

static int rdma_rw_map_sg(struct ib_device *dev, struct scatterlist *sg,
                          u32 sg_cnt, enum dma_data_direction dir)
{
        if (is_pci_p2pdma_page(sg_page(sg))) {
                if (ib_uses_virt_dma(dev))
                        return 0;
                return pci_p2pdma_map_sg(dev->dma_device, sg, sg_cnt, dir);
        }
        return ib_dma_map_sg(dev, sg, sg_cnt, dir);
}

I think the change to rdma_rw_unmap_sg() should probably be dropped in
favour of the above?

Jason
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