Re: [Xen-devel] [PATCH v8 13/19] swiotlb-xen: use xen_dma_map/unmap_page, xen_dma_sync_single_for_cpu/device

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

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@xxxxxxxxxxxxx>
> ---
>  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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