From: Jason Gunthorpe <jgg@nvidia.com>
To: Leon Romanovsky <leon@kernel.org>
Cc: Doug Ledford <dledford@redhat.com>,
Parav Pandit <parav@nvidia.com>, <linux-rdma@vger.kernel.org>
Subject: Re: [PATCH rdma-next] IB/mlx5: Use ib_dma APIs instead of open access to parent device
Date: Mon, 23 Nov 2020 09:59:31 -0400 [thread overview]
Message-ID: <20201123135931.GM917484@nvidia.com> (raw)
In-Reply-To: <20201123082400.351371-1-leon@kernel.org>
On Mon, Nov 23, 2020 at 10:24:00AM +0200, Leon Romanovsky wrote:
> From: Parav Pandit <parav@nvidia.com>
>
> DMA operation of the IB device is done using ib_device->dma_device.
> This is well abstracted using ib_dma APIs.
>
> Hence, instead of doing open access to parent device, use IB core
> provided dma mapping APIs.
Why?
The ib DMA APIs are for people using verbs, they are only needed to
pack things into the ib_sge
If you are inside a driver, not using the verbs API, or not using
ib_sge, then you should not be using the ib_dma API
It is an abberation, we should minimize its use.
> /*
> - * We can't use an array for xlt_emergency_page because dma_map_single doesn't
> + * We can't use an array for xlt_emergency_page because ib_dma_map_single doesn't
> * work on kernel modules memory
> */
> void *xlt_emergency_page;
> @@ -1081,7 +1081,6 @@ static void *mlx5_ib_create_xlt_wr(struct mlx5_ib_mr *mr,
> unsigned int flags)
> {
> struct mlx5_ib_dev *dev = mr->dev;
> - struct device *ddev = dev->ib_dev.dev.parent;
Though this looks wrong, it should be dev->mdev->pdev.dev
ie it is always OK to use a PCI device with the normal DMA API
Jason
next prev parent reply other threads:[~2020-11-23 13:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-23 8:24 [PATCH rdma-next] IB/mlx5: Use ib_dma APIs instead of open access to parent device Leon Romanovsky
2020-11-23 13:59 ` Jason Gunthorpe [this message]
2020-11-24 3:34 ` Parav Pandit
2020-11-24 5:20 ` Leon Romanovsky
2020-11-24 12:58 ` Jason Gunthorpe
2020-11-24 9:31 ` Christoph Hellwig
2020-11-24 9:46 ` Leon Romanovsky
2020-11-24 9:49 ` Christoph Hellwig
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