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SubjectRe: [PATCH 4/8] xen/gntdev: Allow mappings for DMA buffers
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On 05/25/2018 11:33 AM, Oleksandr Andrushchenko wrote:
>
> struct unmap_notify {
> @@ -96,10 +104,28 @@ struct grant_map {
> struct gnttab_unmap_grant_ref *kunmap_ops;
> struct page **pages;
> unsigned long pages_vm_start;
> +
> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
> + /*
> + * If dmabuf_vaddr is not NULL then this mapping is backed by DMA
> + * capable memory.
> + */
> +
> + /* Device for which DMA memory is allocated. */
> + struct device *dma_dev;
> + /* Flags used to create this DMA buffer: GNTDEV_DMABUF_FLAG_XXX. */
> + bool dma_flags;

Again, I think most of the comments here can be dropped. Except possibly
for the flags.

> + /* Virtual/CPU address of the DMA buffer. */
> + void *dma_vaddr;
> + /* Bus address of the DMA buffer. */
> + dma_addr_t dma_bus_addr;
> +#endif
> };
>
> static int unmap_grant_pages(struct grant_map *map, int offset, int pages);
>
> +static struct miscdevice gntdev_miscdev;
> +
> /* ------------------------------------------------------------------ */
>
> static void gntdev_print_maps(struct gntdev_priv *priv,
> @@ -121,8 +147,26 @@ 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.nr_pages = map->count;
> + args.pages = map->pages;
> + args.vaddr = map->dma_vaddr;
> + args.dev_bus_addr = map->dma_bus_addr;
> +
> + gnttab_dma_free_pages(&args);
> + } else if (map->pages) {
> + gnttab_free_pages(map->count, map->pages);
> + }
> +#else
> if (map->pages)
> gnttab_free_pages(map->count, map->pages);
> +#endif
> +

} else
#endif
    if (map->pages)
        gnttab_free_pages(map->count, map->pages);


(and elsewhere)

> kfree(map->pages);
> kfree(map->grants);
> kfree(map->map_ops);



>
> diff --git a/include/uapi/xen/gntdev.h b/include/uapi/xen/gntdev.h
> index 6d1163456c03..2d5a4672f07c 100644
> --- a/include/uapi/xen/gntdev.h
> +++ b/include/uapi/xen/gntdev.h
> @@ -200,4 +200,19 @@ struct ioctl_gntdev_grant_copy {
> /* Send an interrupt on the indicated event channel */
> #define UNMAP_NOTIFY_SEND_EVENT 0x2
>
> +/*
> + * Flags to be used while requesting memory mapping's backing storage
> + * to be allocated with DMA API.
> + */
> +
> +/*
> + * The buffer is backed with memory allocated with dma_alloc_wc.
> + */
> +#define GNTDEV_DMA_FLAG_WC (1 << 1)


Is there a reason you are not using bit 0?

-boris
> +
> +/*
> + * The buffer is backed with memory allocated with dma_alloc_coherent.
> + */
> +#define GNTDEV_DMA_FLAG_COHERENT (1 << 2)
> +
> #endif /* __LINUX_PUBLIC_GNTDEV_H__ */

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