Messages in this thread | | | Subject | Re: [PATCH 3/5] dma-direct: refine dma_direct_alloc zone selection | From | Robin Murphy <> | Date | Thu, 27 Sep 2018 15:30:20 +0100 |
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On 20/09/18 19:52, Christoph Hellwig wrote: > We need to take the DMA offset and encryption bit into account when > selecting a zone. User the opportunity to factor out the zone > selection into a helper for reuse. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > --- > kernel/dma/direct.c | 31 +++++++++++++++++++++---------- > 1 file changed, 21 insertions(+), 10 deletions(-) > > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c > index 81b73a5bba54..3c404e33d946 100644 > --- a/kernel/dma/direct.c > +++ b/kernel/dma/direct.c > @@ -68,6 +68,22 @@ u64 dma_direct_get_required_mask(struct device *dev) > return (1ULL << (fls64(max_dma) - 1)) * 2 - 1; > } > > +static gfp_t __dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask, > + u64 *phys_mask) > +{ > + if (force_dma_unencrypted()) > + *phys_mask = __dma_to_phys(dev, dma_mask); > + else > + *phys_mask = dma_to_phys(dev, dma_mask);
Maybe make phys_to_dma_direct() take u64 instead of phys_addr_t so we can reuse it here?
> + /* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */ > + if (*phys_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS)) > + return GFP_DMA;
If we don't have ZONE_DMA it would in theory be a tiny bit better to fall back to GFP_DMA32 instead of returning 0 here, but I'm not sure it's worth the bother.
> + if (*phys_mask <= DMA_BIT_MASK(32)) > + return GFP_DMA32; > + return 0; > +} > + > static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size) > { > return phys_to_dma_direct(dev, phys) + size - 1 <= > @@ -80,17 +96,13 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, > unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT; > int page_order = get_order(size); > struct page *page = NULL; > + u64 phys_mask; > void *ret; > > /* we always manually zero the memory once we are done: */ > 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)) > - gfp |= GFP_DMA; > - if (dev->coherent_dma_mask <= DMA_BIT_MASK(32) && !(gfp & GFP_DMA)) > - gfp |= GFP_DMA32; > - > + gfp |= __dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask, > + &phys_mask); > again: > /* CMA can be used only in the context which permits sleeping */ > if (gfpflags_allow_blocking(gfp)) { > @@ -109,15 +121,14 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, > page = NULL; > > if (IS_ENABLED(CONFIG_ZONE_DMA32) && > - dev->coherent_dma_mask < DMA_BIT_MASK(64) && > + phys_mask < DMA_BIT_MASK(64) && > !(gfp & (GFP_DMA32 | GFP_DMA))) { > gfp |= GFP_DMA32; > goto again;
Ah right, in that situation we should probably end up here anyway, so that's good enough - definitely not worth any more #ifdeffery above. Nits aside,
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> } > > if (IS_ENABLED(CONFIG_ZONE_DMA) && > - dev->coherent_dma_mask < DMA_BIT_MASK(32) && > - !(gfp & GFP_DMA)) { > + phys_mask < DMA_BIT_MASK(32) && !(gfp & GFP_DMA)) { > gfp = (gfp & ~GFP_DMA32) | GFP_DMA; > goto again; > } >
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