Re: [Xen-devel][RFC 2/3] xen/grant-table: Extend API to work with DMA buffers

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On 05/19/2018 01:19 AM, Boris Ostrovsky wrote:
On 05/17/2018 04:26 AM, Oleksandr Andrushchenko wrote:
From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
---
  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.
Yes, this can be done
-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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