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SubjectRe: [PATCH v2 1/2] dma-direct: check for overflows on 32 bit DMA addresses
On Fri, Oct 18, 2019 at 01:00:43PM +0200, Nicolas Saenz Julienne wrote:
> +#ifndef CONFIG_ARCH_DMA_ADDR_T_64BIT
> + /* Check if DMA address overflowed */
> + if (min(addr, addr + size - 1) <
> + __phys_to_dma(dev, (phys_addr_t)(min_low_pfn << PAGE_SHIFT)))
> + return false;
> +#endif

Would be nice to use IS_ENABLED and PFN_PHYS here, and I also think we
need to use phys_to_dma to take care of the encryption bit. If you then
also introduce an end variable we can make the whole thing actually look
nice:

static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
{
dma_addr_t end = addr + size - 1;

if (!dev->dma_mask)
return false;

if (!IS_ENABLED(CONFIG_ARCH_DMA_ADDR_T_64BIT) &&
min(addr, end) < phys_to_dma(dev, PFN_PHYS(min_low_pfn)))
return false;

return end <= min_not_zero(*dev->dma_mask, dev->bus_dma_mask);
}

Otherwise this looks sensible to me.

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