On Mon, 2018-07-30 at 18:38 +0200, Christoph Hellwig wrote:
> We need to take the DMA offset and encryption bit into account when selecting
> a zone. Add a helper that takes those into account and use it.
That whole "encryption" stuff seems to be completely specific to the
way x86 does memory encryption, or am I mistaken ? It's not clear to me
what that does in practice and how it relates to DMA mappings.
I'm also not sure about that whole business with ZONE_DMA and
ARCH_ZONE_DMA_BITS...
On ppc64, unless you enable swiotlb (which we only do currently on
some embedded platforms), you have all of memory in ZONE_DMA.
[ 0.000000] Zone ranges:
[ 0.000000] DMA [mem 0x0000000000000000-0x0000001fffffffff]
[ 0.000000] DMA32 empty
[ 0.000000] Normal empty
[ 0.000000] Device empty
I'm not sure how this will work with that dma direct code.
I also see a number of tests against a 64-bit mask rather than the
top of memory...
Ben.
> Signed-off-by: Christoph Hellwig <h...@lst.de>
> ---
> kernel/dma/direct.c | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index d32d4f0d2c0c..c2c1df8827f2 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -58,6 +58,14 @@ static bool dma_coherent_ok(struct device *dev,
> phys_addr_t phys, size_t size)
> return addr + size - 1 <= dev->coherent_dma_mask;
> }
>
> +static bool dma_coherent_below(struct device *dev, u64 mask)
> +{
> + dma_addr_t addr = force_dma_unencrypted() ?
> + __phys_to_dma(dev, mask) : phys_to_dma(dev, mask);
> +
> + return dev->coherent_dma_mask <= addr;
> +}
> +
> void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t
> *dma_handle,
> gfp_t gfp, unsigned long attrs)
> {
> @@ -70,9 +78,9 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> dma_addr_t *dma_handle,
> gfp &= ~__GFP_ZERO;
>
> /* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */
> - if (dev->coherent_dma_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
> + if (dma_coherent_below(dev, DMA_BIT_MASK(ARCH_ZONE_DMA_BITS)))
> gfp |= GFP_DMA;
> - if (dev->coherent_dma_mask <= DMA_BIT_MASK(32) && !(gfp & GFP_DMA))
> + if (dma_coherent_below(dev, DMA_BIT_MASK(32) && !(gfp & GFP_DMA)))
> gfp |= GFP_DMA32;
>
> again:
> @@ -92,14 +100,14 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> dma_addr_t *dma_handle,
> page = NULL;
>
> if (IS_ENABLED(CONFIG_ZONE_DMA32) &&
> - dev->coherent_dma_mask < DMA_BIT_MASK(64) &&
> + dma_coherent_below(dev, DMA_BIT_MASK(64)) &&
> !(gfp & (GFP_DMA32 | GFP_DMA))) {
> gfp |= GFP_DMA32;
> goto again;
> }
>
> if (IS_ENABLED(CONFIG_ZONE_DMA) &&
> - dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
> + dma_coherent_below(dev, DMA_BIT_MASK(32)) &&
> !(gfp & GFP_DMA)) {
> gfp = (gfp & ~GFP_DMA32) | GFP_DMA;
> goto again;
