On Thu, Aug 29, 2013 at 07:32:32PM +0100, Stefano Stabellini wrote:

xen_swiotlb_alloc_coherent needs to allocate a coherent buffer for cpu
and devices. On native x86 and ARMv8 is sufficient to call
__get_free_pages in order to get a coherent buffer, while on ARM we need
to call arm_dma_ops.alloc.

Don't bet on this for ARMv8. It's not mandated for the architecture, so
at some point some SoC will require non-cacheable buffers for coherency.

-- 
Catalin