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Subject[PATCH 3/3] xen/swiotlb: remember having called xen_create_contiguous_region()
Date
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@suse.com>
---
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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