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From: Jason Gunthorpe <jgg@ziepe.ca>
To: "Christian König" <christian.koenig@amd.com>
Cc: Daniel Vetter <daniel@ffwll.ch>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	"moderated list:DMA BUFFER SHARING FRAMEWORK" 
	<linaro-mm-sig@lists.linaro.org>, Linux MM <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	"open list:DMA BUFFER SHARING FRAMEWORK" 
	<linux-media@vger.kernel.org>
Subject: Re: [Linaro-mm-sig] Changing vma->vm_file in dma_buf_mmap()
Date: Thu, 17 Sep 2020 13:39:07 -0300	[thread overview]
Message-ID: <20200917163907.GI8409@ziepe.ca> (raw)
In-Reply-To: <b9e65f47-b5c8-db09-117a-a8e22a5b6c71@amd.com>

On Thu, Sep 17, 2020 at 06:06:14PM +0200, Christian König wrote:
> > > If it is already taking a page fault I'm not sure the extra function
> > > call indirection is going to be a big deal. Having a uniform VMA
> > > sounds saner than every driver custom rolling something.
> > > 
> > > When I unwound a similar mess in RDMA all the custom VMA stuff in the
> > > drivers turned out to be generally buggy, at least.
> > > 
> > > Is vma->vm_file->private_data universally a dma_buf pointer at least?
> > Nope. I think if you want this without some large scale rewrite of a
> > lot of code we'd need a vmops->get_dmabuf or similar. Not pretty, but
> > would get the job done.
> 
> Yeah, agree that sounds like the simplest approach.

I don't think that will fly, it is clearly only papering over a mess
inside DRM/dma buf :\

Jason

  reply	other threads:[~2020-09-17 16:40 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-14 13:29 Changing vma->vm_file in dma_buf_mmap() Christian König
2020-09-14 13:29 ` [PATCH 1/2] drm/shmem-helpers: revert "Redirect mmap for imported dma-buf" Christian König
2020-09-15 10:39   ` Daniel Vetter
2020-09-15 11:03     ` Christian König
2020-09-15 11:07       ` Daniel Vetter
2020-09-14 13:29 ` [PATCH 2/2] mm: introduce vma_set_file function Christian König
2020-09-15  9:19   ` kernel test robot
2020-09-15 11:57   ` kernel test robot
2020-09-14 13:30 ` Changing vma->vm_file in dma_buf_mmap() Christian König
2020-09-14 14:06   ` Jason Gunthorpe
2020-09-14 18:26     ` Christian König
2020-09-16  9:53       ` Daniel Vetter
     [not found]         ` <fc8f2af7-9fc2-cb55-3065-75a4060b7c82@amd.com>
     [not found]           ` <b621db68-30b9-cc3f-c2c0-237a7fe4db09@amd.com>
2020-09-16 12:41             ` Daniel Vetter
2020-09-16 14:07         ` Jason Gunthorpe
2020-09-16 14:14           ` Christian König
2020-09-16 15:24             ` Daniel Vetter
2020-09-16 15:31               ` [Linaro-mm-sig] " Christian König
2020-09-17  6:23                 ` Daniel Vetter
2020-09-17  7:11                   ` Christian König
2020-09-17  8:09                     ` Daniel Vetter
2020-09-17 11:31                       ` Jason Gunthorpe
2020-09-17 12:03                         ` Christian König
2020-09-17 12:18                           ` Jason Gunthorpe
2020-09-17 12:24                             ` Christian König
2020-09-17 12:26                               ` Daniel Vetter
2020-09-17 14:35                               ` Jason Gunthorpe
2020-09-17 14:54                                 ` Christian König
2020-09-17 15:24                                   ` Jason Gunthorpe
2020-09-17 15:37                                     ` Daniel Vetter
2020-09-17 16:06                                       ` Christian König
2020-09-17 16:39                                         ` Jason Gunthorpe [this message]
2020-09-17 17:23                                           ` Daniel Vetter

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