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From: Daniel Vetter <daniel@ffwll.ch>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Daniel Vetter <daniel@ffwll.ch>,
	"Xiong, Jianxin" <jianxin.xiong@intel.com>,
	Leon Romanovsky <leon@kernel.org>,
	"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	Doug Ledford <dledford@redhat.com>,
	"Vetter, Daniel" <daniel.vetter@intel.com>,
	Christian Koenig <christian.koenig@amd.com>
Subject: Re: [RFC PATCH v3 1/4] RDMA/umem: Support importing dma-buf as user memory region
Date: Tue, 6 Oct 2020 18:34:20 +0200	[thread overview]
Message-ID: <20201006163420.GB438822@phenom.ffwll.local> (raw)
In-Reply-To: <20201006154956.GI5177@ziepe.ca>

On Tue, Oct 06, 2020 at 12:49:56PM -0300, Jason Gunthorpe wrote:
> On Tue, Oct 06, 2020 at 11:22:14AM +0200, Daniel Vetter wrote:
> > 
> > For reinstanting the pages you need:
> > 
> > - dma_resv_lock, this prevents anyone else from issuing new moves or
> >   anything like that
> > - dma_resv_get_excl + dma_fence_wait to wait for any pending moves to
> >   finish. gpus generally don't wait on the cpu, but block the dependent
> >   dma operations from being scheduled until that fence fired. But for rdma
> >   odp I think you need the cpu wait in your worker here.
> 
> Reinstating is not really any different that the first insertion, so
> then all this should be needed in every case?

Yes. Without move_notify we pin the dma-buf into system memory, so it
can't move, and hence you also don't have to chase it. But with
move_notify this all becomes possible.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

WARNING: multiple messages have this Message-ID (diff)
From: Daniel Vetter <daniel@ffwll.ch>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Leon Romanovsky <leon@kernel.org>,
	"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	Doug Ledford <dledford@redhat.com>,
	"Vetter, Daniel" <daniel.vetter@intel.com>,
	Christian Koenig <christian.koenig@amd.com>,
	"Xiong, Jianxin" <jianxin.xiong@intel.com>
Subject: Re: [RFC PATCH v3 1/4] RDMA/umem: Support importing dma-buf as user memory region
Date: Tue, 6 Oct 2020 18:34:20 +0200	[thread overview]
Message-ID: <20201006163420.GB438822@phenom.ffwll.local> (raw)
In-Reply-To: <20201006154956.GI5177@ziepe.ca>

On Tue, Oct 06, 2020 at 12:49:56PM -0300, Jason Gunthorpe wrote:
> On Tue, Oct 06, 2020 at 11:22:14AM +0200, Daniel Vetter wrote:
> > 
> > For reinstanting the pages you need:
> > 
> > - dma_resv_lock, this prevents anyone else from issuing new moves or
> >   anything like that
> > - dma_resv_get_excl + dma_fence_wait to wait for any pending moves to
> >   finish. gpus generally don't wait on the cpu, but block the dependent
> >   dma operations from being scheduled until that fence fired. But for rdma
> >   odp I think you need the cpu wait in your worker here.
> 
> Reinstating is not really any different that the first insertion, so
> then all this should be needed in every case?

Yes. Without move_notify we pin the dma-buf into system memory, so it
can't move, and hence you also don't have to chase it. But with
move_notify this all becomes possible.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

  reply	other threads:[~2020-10-06 16:34 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-04 19:12 [RFC PATCH v3 0/4] RDMA: Add dma-buf support Jianxin Xiong
2020-10-04 19:12 ` Jianxin Xiong
2020-10-04 19:12 ` [RFC PATCH v3 1/4] RDMA/umem: Support importing dma-buf as user memory region Jianxin Xiong
2020-10-04 19:12   ` Jianxin Xiong
2020-10-05 10:54   ` Christian König
2020-10-05 10:54     ` Christian König
2020-10-05 16:19     ` Xiong, Jianxin
2020-10-05 16:19       ` Xiong, Jianxin
2020-10-05 13:13   ` Jason Gunthorpe
2020-10-05 13:13     ` Jason Gunthorpe
2020-10-05 16:18     ` Xiong, Jianxin
2020-10-05 16:18       ` Xiong, Jianxin
2020-10-05 16:33       ` Jason Gunthorpe
2020-10-05 16:33         ` Jason Gunthorpe
2020-10-05 19:41         ` Xiong, Jianxin
2020-10-05 19:41           ` Xiong, Jianxin
2020-10-06  9:22       ` Daniel Vetter
2020-10-06  9:22         ` Daniel Vetter
2020-10-06 15:26         ` Xiong, Jianxin
2020-10-06 15:26           ` Xiong, Jianxin
2020-10-06 15:49         ` Jason Gunthorpe
2020-10-06 15:49           ` Jason Gunthorpe
2020-10-06 16:34           ` Daniel Vetter [this message]
2020-10-06 16:34             ` Daniel Vetter
2020-10-06 17:24             ` Daniel Vetter
2020-10-06 17:24               ` Daniel Vetter
2020-10-06 18:02               ` Jason Gunthorpe
2020-10-06 18:02                 ` Jason Gunthorpe
2020-10-06 18:17                 ` Daniel Vetter
2020-10-06 18:17                   ` Daniel Vetter
2020-10-06 18:38                   ` Jason Gunthorpe
2020-10-06 18:38                     ` Jason Gunthorpe
2020-10-06 19:12                     ` Daniel Vetter
2020-10-06 19:12                       ` Daniel Vetter
2020-10-07  7:13                       ` Christian König
2020-10-07  7:13                         ` Christian König
2020-10-06 16:40       ` Daniel Vetter
2020-10-06 16:40         ` Daniel Vetter
2020-10-04 19:12 ` [RFC PATCH v3 2/4] RDMA: Expand driver memory registration methods to support dma-buf Jianxin Xiong
2020-10-04 19:12   ` Jianxin Xiong
2020-10-04 19:12 ` [RFC PATCH v3 3/4] RDMA/mlx5: Support dma-buf based userspace memory region Jianxin Xiong
2020-10-04 19:12   ` Jianxin Xiong
2020-10-04 19:12 ` [RFC PATCH v3 4/4] RDMA/uverbs: Add uverbs command for dma-buf based MR registration Jianxin Xiong
2020-10-04 19:12   ` Jianxin Xiong

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