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SubjectRe: [PATCH v8 13/19] swiotlb-xen: use xen_dma_map/unmap_page, xen_dma_sync_single_for_cpu/device
On Thu, Oct 17, 2013 at 06:43:28PM +0100, Stefano Stabellini wrote:
> Call xen_dma_map_page, xen_dma_unmap_page, xen_dma_sync_single_for_cpu,
> xen_dma_sync_single_for_device from swiotlb-xen to ensure cpu/device
> coherency of the pages used for DMA, including the ones belonging to the
> swiotlb buffer.

You lost me.

Isn't it the driver's responsibility to do this?

Looking at what 'xen_dma_map_page()' does for x86 it looks to add an extra
call - page_to_phys - and we ignore it here.

>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> ---
> drivers/xen/swiotlb-xen.c | 39 +++++++++++++++++++++++++++++++--------
> 1 files changed, 31 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index 189b8db..4221cb5 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -378,8 +378,13 @@ dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
> * buffering it.
> */
> if (dma_capable(dev, dev_addr, size) &&
> - !range_straddles_page_boundary(phys, size) && !swiotlb_force)
> + !range_straddles_page_boundary(phys, size) && !swiotlb_force) {
> + /* we are not interested in the dma_addr returned by
> + * xen_dma_map_page, only in the potential cache flushes executed
> + * by the function. */
> + xen_dma_map_page(dev, page, offset, size, dir, attrs);
> return dev_addr;
> + }
>
> /*
> * Oh well, have to allocate and map a bounce buffer.
> @@ -388,6 +393,8 @@ dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
> if (map == SWIOTLB_MAP_ERROR)
> return DMA_ERROR_CODE;
>
> + xen_dma_map_page(dev, pfn_to_page(map >> PAGE_SHIFT),
> + map & ~PAGE_MASK, size, dir, attrs);
> dev_addr = xen_phys_to_bus(map);
>
> /*
> @@ -410,12 +417,15 @@ EXPORT_SYMBOL_GPL(xen_swiotlb_map_page);
> * whatever the device wrote there.
> */
> static void xen_unmap_single(struct device *hwdev, dma_addr_t dev_addr,
> - size_t size, enum dma_data_direction dir)
> + size_t size, enum dma_data_direction dir,
> + struct dma_attrs *attrs)
> {
> phys_addr_t paddr = xen_bus_to_phys(dev_addr);
>
> BUG_ON(dir == DMA_NONE);
>
> + xen_dma_unmap_page(hwdev, paddr, size, dir, attrs);
> +
> /* NOTE: We use dev_addr here, not paddr! */
> if (is_xen_swiotlb_buffer(dev_addr)) {
> swiotlb_tbl_unmap_single(hwdev, paddr, size, dir);
> @@ -438,7 +448,7 @@ void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
> size_t size, enum dma_data_direction dir,
> struct dma_attrs *attrs)
> {
> - xen_unmap_single(hwdev, dev_addr, size, dir);
> + xen_unmap_single(hwdev, dev_addr, size, dir, attrs);
> }
> EXPORT_SYMBOL_GPL(xen_swiotlb_unmap_page);
>
> @@ -461,11 +471,15 @@ xen_swiotlb_sync_single(struct device *hwdev, dma_addr_t dev_addr,
>
> BUG_ON(dir == DMA_NONE);
>
> + if (target == SYNC_FOR_CPU)
> + xen_dma_sync_single_for_cpu(hwdev, paddr, size, dir);
> +
> /* NOTE: We use dev_addr here, not paddr! */
> - if (is_xen_swiotlb_buffer(dev_addr)) {
> + if (is_xen_swiotlb_buffer(dev_addr))
> swiotlb_tbl_sync_single(hwdev, paddr, size, dir, target);
> - return;
> - }
> +
> + if (target == SYNC_FOR_DEVICE)
> + xen_dma_sync_single_for_cpu(hwdev, paddr, size, dir);
>
> if (dir != DMA_FROM_DEVICE)
> return;
> @@ -536,8 +550,17 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
> return DMA_ERROR_CODE;
> }
> sg->dma_address = xen_phys_to_bus(map);
> - } else
> + } else {
> + /* we are not interested in the dma_addr returned by
> + * xen_dma_map_page, only in the potential cache flushes executed
> + * by the function. */
> + xen_dma_map_page(hwdev, pfn_to_page(paddr >> PAGE_SHIFT),
> + paddr & ~PAGE_MASK,
> + sg->length,
> + dir,
> + attrs);
> sg->dma_address = dev_addr;
> + }
> sg_dma_len(sg) = sg->length;
> }
> return nelems;
> @@ -559,7 +582,7 @@ xen_swiotlb_unmap_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
> BUG_ON(dir == DMA_NONE);
>
> for_each_sg(sgl, sg, nelems, i)
> - xen_unmap_single(hwdev, sg->dma_address, sg_dma_len(sg), dir);
> + xen_unmap_single(hwdev, sg->dma_address, sg_dma_len(sg), dir, attrs);
>
> }
> EXPORT_SYMBOL_GPL(xen_swiotlb_unmap_sg_attrs);
> --
> 1.7.2.5
>


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