Re: [PATCH 02/20] kernel/dma/direct: refine dma_direct_alloc zone selection
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: 2018-08-08 23:55:00
Also in:
linux-iommu
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.
quoted hunk ↗ jump to hunk
Signed-off-by: Christoph Hellwig <hch@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;