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SubjectRe: [RFC PATCH v3 4/6] swiotlb: Add restricted DMA alloc/free support.
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On 1/5/21 7:41 PM, Claire Chang wrote:
> Add the functions, swiotlb_alloc and swiotlb_free to support the
> memory allocation from restricted DMA pool.
>
> Signed-off-by: Claire Chang <tientzu@chromium.org>
> ---

[snip]

> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index 30ccbc08e229..126e9b3354d6 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -137,6 +137,11 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> void *ret;
> int err;
>
> +#ifdef CONFIG_SWIOTLB
> + if (unlikely(dev->dma_io_tlb_mem))
> + return swiotlb_alloc(dev, size, dma_handle, attrs);
> +#endif

While this is potentially a hot path, I am not sure of the unkikely is
warranted, maybe best left as a plain conditional.
--
Florian

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