[PATCH] powerpc/dma: Fix invalid DMA mmap behavior

[Michael Ellerman]

On Wed, 2019-07-17 at 23:54:37 UTC, Shawn Anastasio wrote:
> The refactor of powerpc DMA functions in commit 6666cc17d780
> ("powerpc/dma: remove dma_nommu_mmap_coherent") incorrectly
> changes the way DMA mappings are handled on powerpc.
> Since this change, all mapped pages are marked as cache-inhibited
> through the default implementation of arch_dma_mmap_pgprot.
> This differs from the previous behavior of only marking pages
> in noncoherent mappings as cache-inhibited and has resulted in
> sporadic system crashes in certain hardware configurations and
> workloads (see Bugzilla).
> 
> This commit restores the previous correct behavior by providing
> an implementation of arch_dma_mmap_pgprot that only marks
> pages in noncoherent mappings as cache-inhibited. As this behavior
> should be universal for all powerpc platforms a new file,
> dma-generic.c, was created to store it.
> 
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=204145
> Fixes: 6666cc17d780 ("powerpc/dma: remove dma_nommu_mmap_coherent")
> Signed-off-by: Shawn Anastasio <shawn at anastas.io>
> Reviewed-by: Alexey Kardashevskiy <aik at ozlabs.ru>
> Reviewed-by: Christoph Hellwig <hch at lst.de>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/b4fc36e60f25cf22bf8b7b015a701015740c3743

cheers