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

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Message-ID: <b78251d7-462a-fb1f-32e9-868a7236decb@oracle.com>
Date:   Tue, 12 Jun 2018 21:26:49 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Oleksandr Andrushchenko <andr2000@...il.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-media@...r.kernel.org,
        jgross@...e.com, konrad.wilk@...cle.com
Cc:     daniel.vetter@...el.com, dongwon.kim@...el.com,
        matthew.d.roper@...el.com,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
Subject: 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@...cle.com>