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From: Gal Pressman <galpress@amazon.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: "Daniel Vetter" <daniel@ffwll.ch>,
	"Sumit Semwal" <sumit.semwal@linaro.org>,
	"Christian König" <christian.koenig@amd.com>,
	"Doug Ledford" <dledford@redhat.com>,
	"open list:DMA BUFFER SHARING FRAMEWORK"
	<linux-media@vger.kernel.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	linux-rdma <linux-rdma@vger.kernel.org>,
	"Oded Gabbay" <ogabbay@habana.ai>,
	"Tomer Tayar" <ttayar@habana.ai>,
	"Yossi Leybovich" <sleybo@amazon.com>,
	"Alexander Matushevsky" <matua@amazon.com>,
	"Leon Romanovsky" <leonro@nvidia.com>,
	"Jianxin Xiong" <jianxin.xiong@intel.com>,
	"John Hubbard" <jhubbard@nvidia.com>
Subject: Re: [RFC] Make use of non-dynamic dmabuf in RDMA
Date: Sat, 21 Aug 2021 12:16:08 +0300	[thread overview]
Message-ID: <da6364b7-9621-a384-23b0-9aa88ae232e5@amazon.com> (raw)
In-Reply-To: <20210820143248.GX543798@ziepe.ca>

On 20/08/2021 17:32, Jason Gunthorpe wrote:
> On Fri, Aug 20, 2021 at 03:58:33PM +0300, Gal Pressman wrote:
> 
>> Though it would've been nicer if we could agree on a solution that could work
>> for more than 1-2 RDMA devices, using the existing tools the RDMA subsystem has.
> 
> I don't think it can really be done, revoke is necessary, and isn't a
> primitive we have today.
> 
> Revoke is sort of like rereg MR, but with a guaranteed no-change to
> the lkey/rkey
> 
> Then there is the locking complexity of linking the mr creation and
> destruction to the lifecycle of the pages, which is messy and maybe
> not general. For instance mlx5 would call its revoke_mr, disconnect
> the dmabuf then destroy the mkey - but this is only safe because mlx5
> HW can handle concurrent revokes.

Thanks, that makes sense.

>> That's why I tried to approach this by denying such attachments for non-ODP
>> importers instead of exposing a "limited" dynamic importer.
> 
> That is fine if there is no revoke - once revoke exists we must have
> driver and HW support.

Agree.
IIUC, we're talking about three different exporter "types":
- Dynamic with move_notify (requires ODP)
- Dynamic with revoke_notify
- Static

Which changes do we need to make the third one work?

  reply	other threads:[~2021-08-21  9:16 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18  7:43 [RFC] Make use of non-dynamic dmabuf in RDMA Gal Pressman
2021-08-18  8:00 ` Christian König
2021-08-18  8:37   ` Gal Pressman
2021-08-18  9:34 ` Daniel Vetter
2021-08-19 23:06   ` Jason Gunthorpe
2021-08-20  7:25     ` Daniel Vetter
2021-08-20 12:33       ` Jason Gunthorpe
2021-08-20 12:58         ` Gal Pressman
2021-08-20 14:32           ` Jason Gunthorpe
2021-08-21  9:16             ` Gal Pressman [this message]
2021-08-23 10:43               ` Christian König
2021-08-24  9:06                 ` Gal Pressman
2021-08-24  9:32                   ` Christian König
2021-08-24 17:27                     ` John Hubbard
2021-08-24 17:32                       ` Jason Gunthorpe
2021-08-24 17:35                         ` John Hubbard
2021-08-24 19:15                           ` Dave Airlie
2021-08-24 19:30                             ` Jason Gunthorpe
2021-08-24 19:43                             ` Alex Deucher
2021-08-24 20:00                               ` Xiong, Jianxin
2021-08-25  6:17                         ` Christian König
2021-08-25  6:47                           ` John Hubbard
2021-08-25 12:18                           ` Jason Gunthorpe
2021-08-25 12:27                             ` Christian König
2021-08-25 12:38                               ` Jason Gunthorpe
2021-08-25 13:51                                 ` Christian König
2021-08-25 14:47                                   ` Jason Gunthorpe
2021-08-25 15:14                                     ` Christian König
2021-08-25 15:49                                       ` Jason Gunthorpe
2021-08-25 16:02                                       ` Oded Gabbay
2021-09-01 11:20                         ` Gal Pressman
2021-09-01 11:24                           ` Christian König
2021-09-02  6:56                             ` Gal Pressman

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