[PATCH 6/8] xen/gntdev: Implement dma-buf export functionality

From: Oleksandr Andrushchenko 1. Create a dma-buf from grant references provided by the foreign domain. By default dma-buf is backed by system memory pages, but by providing GNTDEV_DMA_FLAG_XXX flags it can also be created as a DMA

[PATCH 6/8] xen/gntdev: Implement dma-buf export functionality

From: Oleksandr Andrushchenko 1. Create a dma-buf from grant references provided by the foreign domain. By default dma-buf is backed by system memory pages, but by providing GNTDEV_DMA_FLAG_XXX flags it can also be created as a DMA write-combine/coherent buffer, e.g. allocated with