Re: [PATCH for-next 1/3] RDMA/erdma: Use dma_map_page to map scatter MTT buffer

[Leon Romanovsky <leon@kernel.org>]

On Fri, Jul 25, 2025 at 01:53:54PM +0800, Boshi Yu wrote:
> Each high-level indirect MTT entry is assumed to point to exactly one page
> of the low-level MTT buffer, but dma_map_sg may merge contiguous physical
> pages when mapping. To avoid extra overhead from splitting merged regions,
> use dma_map_page to map the scatter MTT buffer page by page.
> 
> Reviewed-by: Cheng Xu <chengyou@linux.alibaba.com>
> Signed-off-by: Boshi Yu <boshiyu@linux.alibaba.com>
> ---
>  drivers/infiniband/hw/erdma/erdma_verbs.c | 110 ++++++++++++++--------
>  drivers/infiniband/hw/erdma/erdma_verbs.h |   4 +-
>  2 files changed, 71 insertions(+), 43 deletions(-)

<...>

> +	pg_dma = vzalloc(npages * sizeof(dma_addr_t));
> +	if (!pg_dma)
> +		return 0;
>  
> -	sg_init_table(sglist, npages);
> +	addr = buf;
>  	for (i = 0; i < npages; i++) {
> -		pg = vmalloc_to_page(buf);
> +		pg = vmalloc_to_page(addr);

<...>
> +
> +		pg_dma[i] = dma_map_page(&dev->pdev->dev, pg, 0, PAGE_SIZE,
> +					 DMA_TO_DEVICE);

Does it work?

Thanks