[Xen-devel] [PATCH 3/3] xen/swiotlb: remember having called xen_create_contiguous_region()

[Juergen Gross <jgross@xxxxxxxx>]

Instead of always calling xen_destroy_contiguous_region() in case the
memory is DMA-able for the used device, do so only in case it has been
made DMA-able via xen_create_contiguous_region() before.

This will avoid a lot of xen_destroy_contiguous_region() calls for
64-bit capable devices.

As the memory in question is owned by swiotlb-xen the PG_owner_priv_1
flag of the first allocated page can be used for remembering.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 drivers/xen/swiotlb-xen.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 43b6e65ae256..a72f181d8e20 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -321,6 +321,7 @@ xen_swiotlb_alloc_coherent(struct device *hwdev, size_t 
size,
                        xen_free_coherent_pages(hwdev, size, ret, 
(dma_addr_t)phys, attrs);
                        return NULL;
                }
+               SetPageOwnerPriv1(virt_to_page(ret));
        }
        memset(ret, 0, size);
        return ret;
@@ -344,9 +345,11 @@ 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) &&
-           !WARN_ON(range_straddles_page_boundary(phys, size)))
-               xen_destroy_contiguous_region(phys, order);
+       if (PageOwnerPriv1(virt_to_page(vaddr))) {
+               if (!WARN_ON(range_straddles_page_boundary(phys, size)))
+                       xen_destroy_contiguous_region(phys, order);
+               ClearPageOwnerPriv1(virt_to_page(vaddr));
+       }
 
        xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs);
 }
-- 
2.16.4


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