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SubjectRe: [Xen-devel][RFC 2/3] xen/grant-table: Extend API to work with DMA buffers
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On 05/17/2018 04:26 AM, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> ---
> drivers/xen/grant-table.c | 49 +++++++++++++++++++++++++++++++++++++++
> include/xen/grant_table.h | 7 ++++++
> 2 files changed, 56 insertions(+)
>
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index bb36b1e1dbcc..c27bcc420575 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -729,6 +729,55 @@ void gnttab_free_pages(int nr_pages, struct page **pages)
> }
> EXPORT_SYMBOL(gnttab_free_pages);
>
> +int gnttab_dma_alloc_pages(struct device *dev, bool coherent,
> + int nr_pages, struct page **pages,
> + void **vaddr, dma_addr_t *dev_bus_addr)
> +{
> + int i;
> + int ret;
> +
> + ret = alloc_dma_xenballooned_pages(dev, coherent, nr_pages, pages,
> + vaddr, dev_bus_addr);
> + if (ret < 0)
> + return ret;
> +
> + for (i = 0; i < nr_pages; i++) {
> +#if BITS_PER_LONG < 64
> + struct xen_page_foreign *foreign;
> +
> + foreign = kzalloc(sizeof(*foreign), GFP_KERNEL);
> + if (!foreign) {
> + gnttab_dma_free_pages(dev, flags, nr_pages, pages,
> + *vaddr, *dev_bus_addr);
> + return -ENOMEM;
> + }
> + set_page_private(pages[i], (unsigned long)foreign);
> +#endif
> + SetPagePrivate(pages[i]);
> + }
> + return 0;
> +}
> +EXPORT_SYMBOL(gnttab_dma_alloc_pages);
> +
> +void gnttab_dma_free_pages(struct device *dev, bool coherent,
> + int nr_pages, struct page **pages,
> + void *vaddr, dma_addr_t dev_bus_addr)
> +{
> + int i;
> +
> + for (i = 0; i < nr_pages; i++) {
> + if (PagePrivate(pages[i])) {
> +#if BITS_PER_LONG < 64
> + kfree((void *)page_private(pages[i]));
> +#endif
> + ClearPagePrivate(pages[i]);
> + }
> + }
> + free_dma_xenballooned_pages(dev, coherent, nr_pages, pages,
> + vaddr, dev_bus_addr);
> +}
> +EXPORT_SYMBOL(gnttab_dma_free_pages);


Given that these routines look almost exactly like their non-dma
counterparts I wonder whether common code could be factored out.

-boris




> +
> /* Handling of paged out grant targets (GNTST_eagain) */
> #define MAX_DELAY 256
> static inline void
> diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
> index 34b1379f9777..20ee2b5ba965 100644
> --- a/include/xen/grant_table.h
> +++ b/include/xen/grant_table.h
> @@ -195,6 +195,13 @@ void gnttab_free_auto_xlat_frames(void);
> int gnttab_alloc_pages(int nr_pages, struct page **pages);
> void gnttab_free_pages(int nr_pages, struct page **pages);
>
> +int gnttab_dma_alloc_pages(struct device *dev, bool coherent,
> + int nr_pages, struct page **pages,
> + void **vaddr, dma_addr_t *dev_bus_addr);
> +void gnttab_dma_free_pages(struct device *dev, bool coherent,
> + int nr_pages, struct page **pages,
> + void *vaddr, dma_addr_t dev_bus_addr);
> +
> int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
> struct gnttab_map_grant_ref *kmap_ops,
> struct page **pages, unsigned int count);

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