Re: [Xen-devel] [PATCH v6 12/19] swiotlb: don't assume that io_tlb_start-io_tlb_end is coherent

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

On Fri, Sep 27, 2013 at 05:10:00PM +0100, Stefano Stabellini wrote:
> The swiotlb code has appropriate calls to dma_mark_clean in place for
> buffers passed to swiotlb_map_page as an argument. However it assumes
> that the swiotlb bounce buffer (io_tlb_start-io_tlb_end) is already
> coherent and doesn't need any calls to dma_mark_clean.
> 
> On ARM the swiotlb bounce buffer is not coherent (the memory is
> writealloc while it should be bufferable) and therefore we need to call
> dma_mark_clean appropriately on the bounce buffer code paths too.
> 
> Note that most architecures have an empty dma_mark_clean implementation
> anyway.

The other architecture that uses swiotlb is IA64 and that does have
an implementation where it touches on page attributes.

Which means I have to figure out why my HP zx6000 won't boot with 3.11 now :-(

> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> ---
>  lib/swiotlb.c |   13 ++++++++++---
>  1 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/swiotlb.c b/lib/swiotlb.c
> index 4e8686c..eb45d17 100644
> --- a/lib/swiotlb.c
> +++ b/lib/swiotlb.c
> @@ -515,6 +515,7 @@ found:
>               io_tlb_orig_addr[index+i] = orig_addr + (i << IO_TLB_SHIFT);
>       if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
>               swiotlb_bounce(orig_addr, tlb_addr, size, DMA_TO_DEVICE);
> +     dma_mark_clean(phys_to_virt(tlb_addr), size);
>  
>       return tlb_addr;
>  }
> @@ -547,7 +548,10 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, 
> phys_addr_t tlb_addr,
>        * First, sync the memory before unmapping the entry
>        */
>       if (orig_addr && ((dir == DMA_FROM_DEVICE) || (dir == 
> DMA_BIDIRECTIONAL)))
> +     {
> +             dma_mark_clean(phys_to_virt(tlb_addr), size);
>               swiotlb_bounce(orig_addr, tlb_addr, size, DMA_FROM_DEVICE);
> +     }
>  
>       /*
>        * Return the buffer to the free list by setting the corresponding
> @@ -587,17 +591,20 @@ void swiotlb_tbl_sync_single(struct device *hwdev, 
> phys_addr_t tlb_addr,
>  
>       switch (target) {
>       case SYNC_FOR_CPU:
> -             if (likely(dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL))
> +             if (likely(dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL)) 
> {
> +                     dma_mark_clean(phys_to_virt(tlb_addr), size);
>                       swiotlb_bounce(orig_addr, tlb_addr,
>                                      size, DMA_FROM_DEVICE);
> +             }
>               else
>                       BUG_ON(dir != DMA_TO_DEVICE);
>               break;
>       case SYNC_FOR_DEVICE:
> -             if (likely(dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL))
> +             if (likely(dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)) {
>                       swiotlb_bounce(orig_addr, tlb_addr,
>                                      size, DMA_TO_DEVICE);
> -             else
> +                     dma_mark_clean(phys_to_virt(tlb_addr), size);
> +             } else
>                       BUG_ON(dir != DMA_FROM_DEVICE);
>               break;
>       default:
> -- 
> 1.7.2.5
> 

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