On 25/04/2019 10:53, Jan Beulich wrote:

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On 23.04.19 at 12:54, jgross@suse.com wrote:

--- a/drivers/xen/swiotlb-xen.c +++ b/drivers/xen/swiotlb-xen.c @@ -360,8 +360,8 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr, /* Convert the size to actually allocated. */ size = 1UL << (order + XEN_PAGE_SHIFT);

• if (((dev_addr + size - 1 <= dma_mask)) ||

•    range_straddles_page_boundary(phys, size))
  

• if ((dev_addr + size - 1 <= dma_mask) &&

•    !WARN_ON(range_straddles_page_boundary(phys, size)))
  

  xen_destroy_contiguous_region(phys, order);

On the allocation side we have

if (((dev_addr + size - 1 <= dma_mask)) && !range_straddles_page_boundary(phys, size)) *dma_handle = dev_addr; else { if (xen_create_contiguous_region(phys, order, fls64(dma_mask), dma_handle) != 0) { xen_free_coherent_pages(hwdev, size, ret, (dma_addr_t)phys, attrs); return NULL; } }

which is (as far as the function call is concerned)

if ((dev_addr + size - 1 > dma_mask) || range_straddles_page_boundary(phys, size)) xen_create_contiguous_region(...);

So I don't think your transformation is correct.

I know that I modified the condition. Calling xen_destroy_contiguous_region() for a non-contiguous region is destructive, so we have to avoid it in any case.

I could be talked into moving both tests into the WARN_ON(), however.

Juergen