Re: [PATCH 14/16] nvme-rdma: Ensure dma support when using p2pdma

[John Hubbard]

On 4/8/21 10:01 AM, Logan Gunthorpe wrote:
> Ensure the dma operations support p2pdma before using the RDMA
> device for P2PDMA. This allows switching the RDMA driver from
> pci_p2pdma_map_sg() to dma_map_sg_p2pdma().

Tentatively, this looks right, but it really should be combined
with a following patch that uses it. Then you don't have to try
to explain, above, why it's needed. :)

> Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> ---
>   drivers/nvme/target/rdma.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/nvme/target/rdma.c b/drivers/nvme/target/rdma.c
> index 6c1f3ab7649c..3ec7e77e5416 100644
> --- a/drivers/nvme/target/rdma.c
> +++ b/drivers/nvme/target/rdma.c
> @@ -414,7 +414,8 @@ static int nvmet_rdma_alloc_rsp(struct nvmet_rdma_device *ndev,
>   	if (ib_dma_mapping_error(ndev->device, r->send_sge.addr))
>   		goto out_free_rsp;
>   
> -	if (!ib_uses_virt_dma(ndev->device))
> +	if (!ib_uses_virt_dma(ndev->device) &&
> +	    dma_pci_p2pdma_supported(&ndev->device->dev))
>   		r->req.p2p_client = &ndev->device->dev;
>   	r->send_sge.length = sizeof(*r->req.cqe);
>   	r->send_sge.lkey = ndev->pd->local_dma_lkey;

thanks,
--
John Hubbard
NVIDIA