[PATCH 07/12] dma-direct: simplify the use atomic pool logic in dma_direct_alloc
Robin Murphy
robin.murphy at arm.com
Mon Oct 16 04:58:47 PDT 2023
On 16/10/2023 6:47 am, Christoph Hellwig wrote:
> The logic in dma_direct_alloc when to use the atomic pool vs remapping
> grew a bit unreadable. Consolidate it into a single check, and clean
> up the set_uncached vs remap logic a bit as well.
Reviewed-by: Robin Murphy <robin.murphy at arm.com>
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> ---
> kernel/dma/direct.c | 25 ++++++++++---------------
> 1 file changed, 10 insertions(+), 15 deletions(-)
>
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index ec410af1d8a14e..1327d04fa32a25 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -234,27 +234,22 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> dma_handle);
>
> /*
> - * Otherwise remap if the architecture is asking for it. But
> - * given that remapping memory is a blocking operation we'll
> - * instead have to dip into the atomic pools.
> + * Otherwise we require the architecture to either be able to
> + * mark arbitrary parts of the kernel direct mapping uncached,
> + * or remapped it uncached.
> */
> + set_uncached = IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED);
> remap = IS_ENABLED(CONFIG_DMA_DIRECT_REMAP);
> - if (remap) {
> - if (dma_direct_use_pool(dev, gfp))
> - return dma_direct_alloc_from_pool(dev, size,
> - dma_handle, gfp);
> - } else {
> - if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED))
> - return NULL;
> - set_uncached = true;
> - }
> + if (!set_uncached && !remap)
> + return NULL;
> }
>
> /*
> - * Decrypting memory may block, so allocate the memory from the atomic
> - * pools if we can't block.
> + * Remapping or decrypting memory may block, allocate the memory from
> + * the atomic pools instead if we aren't allowed block.
> */
> - if (force_dma_unencrypted(dev) && dma_direct_use_pool(dev, gfp))
> + if ((remap || force_dma_unencrypted(dev)) &&
> + dma_direct_use_pool(dev, gfp))
> return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);
>
> /* we always manually zero the memory once we are done */
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