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



On 06/13/2018 04:26 AM, Boris Ostrovsky wrote:


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);

Will fix

+        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.

Will fix

+        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.

Of course

+
+            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.

Will fix

+     * 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>
Thank you,
Oleksandr

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