Re: [RFC PATCH v1 18/18] nvme-pci: use new dma API

Robin Murphy
2024-07-04T15:23:54Z

On 02/07/2024 10:09 am, Leon Romanovsky wrote:
[...]
> +static inline dma_addr_t nvme_dma_link_page(struct page *page,
> + unsigned int poffset,
> + unsigned int len,
> + struct nvme_iod *iod)
> {
> - int i;
> - struct scatterlist *sg;
> + struct dma_iova_attrs *iova = &iod->dma_map->iova;
> + struct dma_iova_state *state = &iod->dma_map->state;
> + dma_addr_t dma_addr;
> + int ret;
> +
> + if (iod->dma_map->use_iova) {
> + phys_addr_t phys = page_to_phys(page) + poffset;

Yeah, there's no way this can possibly work. You can't do the
dev_use_swiotlb() check up-front based on some overall DMA operation
size, but then build that operation out of arbitrarily small fragments
of different physical pages that *could* individually need bouncing to
not break coherency.

Thanks,
Robin.

> +
> + dma_addr = state->iova->addr + state->range_size;
> + ret = dma_link_range(&iod->dma_map->state, phys, len);
> + if (ret)
> + return DMA_MAPPING_ERROR;
> + } else {
> + dma_addr = dma_map_page_attrs(iova->dev, page, poffset, len,
> + iova->dir, iova->attrs);
> + }
> + return dma_addr;
> +}