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swiotlb-xen: use the same foreign page check everywhere 

xen_dma_map_page uses a different and more complicated check for foreign
pages than the other three cache maintainance helpers.  Switch it to the
simpler pfn_valid method a well, and document the scheme with a single
improved comment in xen_dma_map_page.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
This commit is contained in:
Christoph Hellwig 2019-08-26 11:23:44 +02:00
parent 922659ea77
commit c9b6180dbf
1 changed files with 9 additions and 22 deletions
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31
include/xen/arm/page-coherent.h
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@ -53,23 +53,17 @@ static inline void xen_dma_map_page(struct device *hwdev, struct page *page,
dma_addr_t dev_addr, unsigned long offset, size_t size,
enum dma_data_direction dir, unsigned long attrs)
{
unsigned long page_pfn = page_to_xen_pfn(page);
unsigned long dev_pfn = XEN_PFN_DOWN(dev_addr);
unsigned long compound_pages =
(1<<compound_order(page)) * XEN_PFN_PER_PAGE;
bool local = (page_pfn <= dev_pfn) &&
(dev_pfn - page_pfn < compound_pages);
unsigned long pfn = PFN_DOWN(dev_addr);
/*
* Dom0 is mapped 1:1, while the Linux page can span across
* multiple Xen pages, it's not possible for it to contain a
* mix of local and foreign Xen pages. So if the first xen_pfn
* == mfn the page is local otherwise it's a foreign page
* grant-mapped in dom0. If the page is local we can safely
* call the native dma_ops function, otherwise we call the xen
* specific function.
* Dom0 is mapped 1:1, and while the Linux page can span across multiple
* Xen pages, it is not possible for it to contain a mix of local and
* foreign Xen pages. Calling pfn_valid on a foreign mfn will always
* return false, so if pfn_valid returns true the pages is local and we
* can use the native dma-direct functions, otherwise we call the Xen
* specific version.
*/
if (local)
if (pfn_valid(pfn))
dma_direct_map_page(hwdev, page, offset, size, dir, attrs);
else
__xen_dma_map_page(hwdev, page, dev_addr, offset, size, dir, attrs);
@ -79,14 +73,7 @@ static inline void xen_dma_unmap_page(struct device *hwdev, dma_addr_t handle,
size_t size, enum dma_data_direction dir, unsigned long attrs)
{
unsigned long pfn = PFN_DOWN(handle);
/*
* Dom0 is mapped 1:1, while the Linux page can be spanned accross
* multiple Xen page, it's not possible to have a mix of local and
* foreign Xen page. Dom0 is mapped 1:1, so calling pfn_valid on a
* foreign mfn will always return false. If the page is local we can
* safely call the native dma_ops function, otherwise we call the xen
* specific function.
*/
if (pfn_valid(pfn))
dma_direct_unmap_page(hwdev, handle, size, dir, attrs);
else