[PATCH] dma-direct: fix DMA_ATTR_NO_KERNEL_MAPPING

[Christoph Hellwig]

On Tue, Nov 02, 2021 at 11:21:16AM +0800, Walter Wu wrote:
> Our platform is arch64. We need a dynamic allocated buffer from CMA is
> not to read by CPU peculative execution, so we need to remove its
> kernel mapping.

If your CPU speculates into unused kernel direct mappings your have
a worse problem than this, because all the dma coherent allocations for
non-coherent devices still have a cachable direct mapping.  Will
mentioned he wanted to look into getting rid of that mapping now that
the core dma code has the infrastucture for that, so adding him here.