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Re: [PATCH v3 5/9] xen/gntdev: Allow mappings for DMA buffers






On 06/12/2018 09:41 AM, Oleksandr Andrushchenko wrote:

static void gntdev_print_maps(struct gntdev_priv *priv,
@@ -121,8 +146,27 @@ static void gntdev_free_map(struct grant_map *map)
  	if (map == NULL)
  		return;
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+	if (map->dma_vaddr) {
+		struct gnttab_dma_alloc_args args;
+
+		args.dev = map->dma_dev;
+		args.coherent = map->dma_flags & GNTDEV_DMA_FLAG_COHERENT;


args.coherent = !!(map->dma_flags & GNTDEV_DMA_FLAG_COHERENT);


+		args.nr_pages = map->count;
+		args.pages = map->pages;
+		args.frames = map->frames;
+		args.vaddr = map->dma_vaddr;
+		args.dev_bus_addr = map->dma_bus_addr;
+
+		gnttab_dma_free_pages(&args);
+	} else
+#endif
  	if (map->pages)
  		gnttab_free_pages(map->count, map->pages);
+
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+	kfree(map->frames);
+#endif
  	kfree(map->pages);
  	kfree(map->grants);
  	kfree(map->map_ops);
@@ -132,7 +176,8 @@ static void gntdev_free_map(struct grant_map *map)
  	kfree(map);
  }
-static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count)
+static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count,
+					  int dma_flags)
  {
  	struct grant_map *add;
  	int i;
@@ -155,6 +200,37 @@ static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count)
  	    NULL == add->pages)
  		goto err;
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+	add->dma_flags = dma_flags;
+
+	/*
+	 * Check if this mapping is requested to be backed
+	 * by a DMA buffer.
+	 */
+	if (dma_flags & (GNTDEV_DMA_FLAG_WC | GNTDEV_DMA_FLAG_COHERENT)) {
+		struct gnttab_dma_alloc_args args;
+
+		add->frames = kcalloc(count, sizeof(add->frames[0]),
+				      GFP_KERNEL);
+		if (!add->frames)
+			goto err;
+
+		/* Remember the device, so we can free DMA memory. */
+		add->dma_dev = priv->dma_dev;
+
+		args.dev = priv->dma_dev;
+		args.coherent = dma_flags & GNTDEV_DMA_FLAG_COHERENT;


And again here.


+		args.nr_pages = count;
+		args.pages = add->pages;
+		args.frames = add->frames;
+
+		if (gnttab_dma_alloc_pages(&args))
+			goto err;
+
+		add->dma_vaddr = args.vaddr;
+		add->dma_bus_addr = args.dev_bus_addr;
+	} else
+#endif
  	if (gnttab_alloc_pages(count, add->pages))
  		goto err;
@@ -325,6 +401,14 @@ static int map_grant_pages(struct grant_map *map)
  		map->unmap_ops[i].handle = map->map_ops[i].handle;
  		if (use_ptemod)
  			map->kunmap_ops[i].handle = map->kmap_ops[i].handle;
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+		else if (map->dma_vaddr) {
+			unsigned long mfn;


This should be called bfn now.


+
+			mfn = pfn_to_bfn(page_to_pfn(map->pages[i]));
+			map->unmap_ops[i].dev_bus_addr = __pfn_to_phys(mfn);
+		}
+#endif
  	}
  	return err;
  }
@@ -548,6 +632,17 @@ static int gntdev_open(struct inode *inode, struct file *flip)
  	}
flip->private_data = priv;
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+	priv->dma_dev = gntdev_miscdev.this_device;
+
+	/*
+	 * The device is not spawn from a device tree, so arch_setup_dma_ops
+	 * is not called, thus leaving the device with dummy DMA ops.
+	 * Fix this call of_dma_configure() with a NULL node to set


"Fix this by calling ..." I think.


+	 * default DMA ops.
+	 */
+	of_dma_configure(priv->dma_dev, NULL);
+#endif
  	pr_debug("priv %p\n", priv);
return 0;


With those fixed,

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>