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SubjectRe: [PATCH 3/3] xen/swiotlb: remember having called xen_create_contiguous_region()
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On 4/23/19 6:54 AM, Juergen Gross wrote:
> 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.

I think a new enum in pageflags would be useful, and be consistent with
other flag uses.

-boris


>
> 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);
> }

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