On Thu, Jan 10, 2019 at 02:44:31PM +0100, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@xxxxxxx>
>
> The SWIOTLB implementation has a maximum size it can
> allocate dma-handles for. This needs to be exported so that
> device drivers don't try to allocate larger chunks.
>
> This is especially important for block device drivers like
> virtio-blk, that might do DMA through SWIOTLB.
Why not use swiotlb_nr_tbl ? That is how drivers/gpu/drm use to figure if they
need to limit the size of pages.
>
> Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
> ---
> include/linux/swiotlb.h | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> index 7c007ed7505f..0bcc80a97036 100644
> --- a/include/linux/swiotlb.h
> +++ b/include/linux/swiotlb.h
> @@ -72,6 +72,11 @@ static inline bool is_swiotlb_buffer(phys_addr_t paddr)
> return paddr >= io_tlb_start && paddr < io_tlb_end;
> }
>
> +static inline size_t swiotlb_max_alloc_size(void)
> +{
> + return ((1UL << IO_TLB_SHIFT) * IO_TLB_SEGSIZE);
> +}
> +
> bool swiotlb_map(struct device *dev, phys_addr_t *phys, dma_addr_t *dma_addr,
> size_t size, enum dma_data_direction dir, unsigned long attrs);
> void __init swiotlb_exit(void);
> @@ -95,6 +100,13 @@ static inline unsigned int swiotlb_max_segment(void)
> {
> return 0;
> }
> +
> +static inline size_t swiotlb_max_alloc_size(void)
> +{
> + /* There is no limit when SWIOTLB isn't used */
> + return ~0UL;
> +}
> +
> #endif /* CONFIG_SWIOTLB */
>
> extern void swiotlb_print_info(void);
> --
> 2.17.1
>
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