On Thu, Sep 27, 2018 at 11:50:14AM +1000, Benjamin Herrenschmidt wrote: > > - * to be able to satisfy them - either by not supporting more physical > > - * memory, or by providing a ZONE_DMA32. If neither is the case, the > > - * architecture needs to use an IOMMU instead of the direct mapping. > > - */ > > - if (mask < phys_to_dma(dev, DMA_BIT_MASK(32))) > > + u64 min_mask; > > + > > + if (IS_ENABLED(CONFIG_ZONE_DMA)) > > + min_mask = DMA_BIT_MASK(ARCH_ZONE_DMA_BITS); > > + else > > + min_mask = min_t(u64, DMA_BIT_MASK(32), > > + (max_pfn - 1) << PAGE_SHIFT); > > + > > + if (mask >= phys_to_dma(dev, min_mask)) > > return 0; > > nitpick ... to be completely "correct", I would have written > > if (IS_ENABLED(CONFIG_ZONE_DMA)) > min_mask = DMA_BIT_MASK(ARCH_ZONE_DMA_BITS); > else > min_mask = DMA_BIT_MASK(32); > > min_mask = min_t(u64, min_mask, (max_pfn - 1) << PAGE_SHIFT); > > In "theory" it's also ok to have a mask < ZONE_DMA_BITS as long as it's > big enough to fit all memory :-)
Yeah, we could do that.
