Re: [PATCHv3 for-next 1/1] RDMA/irdma: Add support for dmabuf pin memory regions

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Feb 01, 2023 at 11:21:15AM +0800, Zhu Yanjun wrote:
> From: Zhu Yanjun <yanjun.zhu@linux.dev>
> 
> This is a followup to the EFA dmabuf[1]. Irdma driver currently does
> not support on-demand-paging(ODP). So it uses habanalabs as the
> dmabuf exporter, and irdma as the importer to allow for peer2peer
> access through libibverbs.
> 
> In this commit, the function ib_umem_dmabuf_get_pinned() is used.
> This function is introduced in EFA dmabuf[1] which allows the driver
> to get a dmabuf umem which is pinned and does not require move_notify
> callback implementation. The returned umem is pinned and DMA mapped
> like standard cpu umems, and is released through ib_umem_release().
> 
> [1]https://lore.kernel.org/lkml/20211007114018.GD2688930@ziepe.ca/t/
> 
> Signed-off-by: Zhu Yanjun <yanjun.zhu@linux.dev>
> Reviewed-by: Shiraz Saleem <shiraz.saleem@intel.com>
> ---
> V2->V3: Remove unnecessary variable initialization;
>         Use error handler;
> V1->V2: Thanks Shiraz Saleem, he gave me a lot of good suggestions.
>         This commit is based on the shared functions from refactored
>         irdma_reg_user_mr.
> ---
>  drivers/infiniband/hw/irdma/verbs.c | 45 +++++++++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
> 
> diff --git a/drivers/infiniband/hw/irdma/verbs.c b/drivers/infiniband/hw/irdma/verbs.c
> index 6982f38596c8..7525f4cdf6fb 100644
> --- a/drivers/infiniband/hw/irdma/verbs.c
> +++ b/drivers/infiniband/hw/irdma/verbs.c
> @@ -2977,6 +2977,50 @@ static struct ib_mr *irdma_reg_user_mr(struct ib_pd *pd, u64 start, u64 len,
>  	return ERR_PTR(err);
>  }
>  
> +static struct ib_mr *irdma_reg_user_mr_dmabuf(struct ib_pd *pd, u64 start,
> +					      u64 len, u64 virt,
> +					      int fd, int access,
> +					      struct ib_udata *udata)
> +{
> +	struct irdma_device *iwdev = to_iwdev(pd->device);
> +	struct ib_umem_dmabuf *umem_dmabuf;
> +	struct irdma_mr *iwmr;
> +	int err;
> +
> +	if (len > iwdev->rf->sc_dev.hw_attrs.max_mr_size)
> +		return ERR_PTR(-EINVAL);
> +
> +	if (udata->inlen < IRDMA_MEM_REG_MIN_REQ_LEN)
> +		return ERR_PTR(-EINVAL);

Shiraz is correct, I'm wondering how this even works. This is a new
style uAPI without UVERBS_ATTR_UHW so inlen should always be 0.

How did you manage to test this??

Jason