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From: Christoph Hellwig <hch@infradead.org>
To: Shunsuke Mie <mie@igel.co.jp>
Cc: Christoph Hellwig <hch@infradead.org>,
	Zhu Yanjun <zyjzyj2000@gmail.com>,
	Christian K??nig <christian.koenig@amd.com>,
	Alex Deucher <alexander.deucher@amd.com>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	Doug Ledford <dledford@redhat.com>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	Jianxin Xiong <jianxin.xiong@intel.com>,
	Leon Romanovsky <leon@kernel.org>,
	linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org,
	Damian Hobson-Garcia <dhobsong@igel.co.jp>,
	Takanari Hayama <taki@igel.co.jp>,
	Tomohito Esaki <etom@igel.co.jp>
Subject: Re: [RFC PATCH 1/3] RDMA/umem: Change for rdma devices has not dma device
Date: Wed, 8 Sep 2021 08:19:11 +0100	[thread overview]
Message-ID: <YThj70ByPvZNQjgU@infradead.org> (raw)
In-Reply-To: <CANXvt5ojNPpyPVnE0D5o9873hGz6ijF7QfTd9z08Ds-ex3Ye-Q@mail.gmail.com>

On Wed, Sep 08, 2021 at 04:01:14PM +0900, Shunsuke Mie wrote:
> Thank you for your comment.
> >
> > On Wed, Sep 08, 2021 at 03:16:09PM +0900, Shunsuke Mie wrote:
> > > To share memory space using dma-buf, a API of the dma-buf requires dma
> > > device, but devices such as rxe do not have a dma device. For those case,
> > > change to specify a device of struct ib instead of the dma device.
> >
> > So if dma-buf doesn't actually need a device to dma map why do we ever
> > pass the dma_device here?  Something does not add up.
> As described in the dma-buf api guide [1], the dma_device is used by dma-buf
> exporter to know the device buffer constraints of importer.
> [1] https://lwn.net/Articles/489703/

Which means for rxe you'd also have to pass the one for the underlying
net device.

  reply	other threads:[~2021-09-08  7:21 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-08  6:16 [RFC PATCH 0/3] RDMA/rxe: Add dma-buf support Shunsuke Mie
2021-09-08  6:16 ` [RFC PATCH 1/3] RDMA/umem: Change for rdma devices has not dma device Shunsuke Mie
2021-09-08  6:26   ` Christoph Hellwig
2021-09-08  7:01     ` Shunsuke Mie
2021-09-08  7:19       ` Christoph Hellwig [this message]
2021-09-08  8:41         ` Shunsuke Mie
2021-09-08 11:18           ` Jason Gunthorpe
2021-09-08 13:33             ` Christian König
2021-09-08 19:22               ` Daniel Vetter
2021-09-08 23:33                 ` Jason Gunthorpe
2021-09-09  9:26                   ` Daniel Vetter
2021-09-10  1:46                     ` Shunsuke Mie
2021-09-13 19:22                       ` Daniel Vetter
2021-09-14  7:11                         ` Shunsuke Mie
2021-09-14  9:38                           ` Daniel Vetter
2021-09-14 10:13                             ` Shunsuke Mie
2021-09-08  6:16 ` [RFC PATCH 2/3] RDMA/rxe: Extract a mapping process into a function Shunsuke Mie
2021-09-08  6:16 ` [RFC PATCH 3/3] RDMA/rxe: Support dma-buf as memory region Shunsuke Mie
2021-09-08  9:29   ` kernel test robot
2021-09-09  3:23   ` kernel test robot
2021-09-09  3:23     ` kernel test robot
2021-09-09  5:45 ` [RFC PATCH 0/3] RDMA/rxe: Add dma-buf support Zhu Yanjun
2021-09-10  2:00   ` Shunsuke Mie

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