Re: [PATCH v1 04/17] dma-mapping: Add check if IOVA can be used

[Zhu Yanjun <yanjun.zhu@linux.dev>]

在 2024/10/30 16:12, Leon Romanovsky 写道:
> From: Leon Romanovsky <leonro@nvidia.com>
> 
> This patch adds a check if IOVA can be used for the specific
> transaction.
> 
> In the new API a DMA mapping transaction is identified by a
> struct dma_iova_state, which holds some recomputed information
> for the transaction which does not change for each page being
> mapped.
> 
> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> ---
>   include/linux/dma-mapping.h | 33 +++++++++++++++++++++++++++++++++
>   1 file changed, 33 insertions(+)
> 
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index 1524da363734..6075e0708deb 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -76,6 +76,20 @@
>   
>   #define DMA_BIT_MASK(n)	(((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
>   
> +struct dma_iova_state {
> +	size_t __size;
> +};
> +
> +/*
> + * Use the high bit to mark if we used swiotlb for one or more ranges.
> + */
> +#define DMA_IOVA_USE_SWIOTLB		(1ULL << 63)

A trivial problem.
In the above macro, using BIT_ULL(63) is better?

Zhu Yanjun

> +
> +static inline size_t dma_iova_size(struct dma_iova_state *state)
> +{
> +	return state->__size & ~DMA_IOVA_USE_SWIOTLB;
> +}
> +
>   #ifdef CONFIG_DMA_API_DEBUG
>   void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
>   void debug_dma_map_single(struct device *dev, const void *addr,
> @@ -281,6 +295,25 @@ static inline int dma_mmap_noncontiguous(struct device *dev,
>   }
>   #endif /* CONFIG_HAS_DMA */
>   
> +#ifdef CONFIG_IOMMU_DMA
> +/**
> + * dma_use_iova - check if the IOVA API is used for this state
> + * @state: IOVA state
> + *
> + * Return %true if the DMA transfers uses the dma_iova_*() calls or %false if
> + * they can't be used.
> + */
> +static inline bool dma_use_iova(struct dma_iova_state *state)
> +{
> +	return state->__size != 0;
> +}
> +#else /* CONFIG_IOMMU_DMA */
> +static inline bool dma_use_iova(struct dma_iova_state *state)
> +{
> +	return false;
> +}
> +#endif /* CONFIG_IOMMU_DMA */
> +
>   #if defined(CONFIG_HAS_DMA) && defined(CONFIG_DMA_NEED_SYNC)
>   void __dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, size_t size,
>   		enum dma_data_direction dir);