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From: Ira Weiny <ira.weiny@intel.com>
To: Thomas Ruf <freelancer@rufusul.de>
Cc: Dave Jiang <dave.jiang@intel.com>, Vinod Koul <vkoul@kernel.org>,
	Federico Vaga <federico.vaga@cern.ch>,
	Dan Williams <dan.j.williams@intel.com>,
	dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, "Kumar,
	Sanjay K" <sanjay.k.kumar@intel.com>,
	"Luck, Tony" <tony.luck@intel.com>
Subject: Re: DMA Engine: Transfer From Userspace
Date: Fri, 26 Jun 2020 13:08:15 -0700
Message-ID: <20200626200815.GC2454695@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <84270660.632865.1593072688966@mailbusiness.ionos.de>

On Thu, Jun 25, 2020 at 10:11:28AM +0200, Thomas Ruf wrote:
> 
> > On 25 June 2020 at 02:42 Dave Jiang <dave.jiang@intel.com> wrote:
> > 
> > 
> > 
> > 
> > On 6/21/2020 12:24 AM, Vinod Koul wrote:
> > > On 19-06-20, 16:31, Dave Jiang wrote:
> > >>
> > >>
> > >> On 6/19/2020 3:47 PM, Federico Vaga wrote:
> > >>> Hello,
> > >>>
> > >>> is there the possibility of using a DMA engine channel from userspace?
> > >>>
> > >>> Something like:
> > >>> - configure DMA using ioctl() (or whatever configuration mechanism)
> > >>> - read() or write() to trigger the transfer
> > >>>
> > >>
> > >> I may have supposedly promised Vinod to look into possibly providing
> > >> something like this in the future. But I have not gotten around to do that
> > >> yet. Currently, no such support.
> > > 
> > > And I do still have serious reservations about this topic :) Opening up
> > > userspace access to DMA does not sound very great from security point of
> > > view.
> > 
> > What about doing it with DMA engine that supports PASID? That way the user can 
> > really only trash its own address space and kernel is protected.
> 
> Sounds interesting! Not sure if this is really needed in that case...
> I have already implemented checks of vm_area_struct for contiguous memory or even do a get_user_pages_fast for user memory to pin it (hope that is the correct term here). Of course i have to do that for every involved page.

FWIW there is a new pin_user_pages_fast()/unpin_user_page() interface now.

Ira

> But i will do some checks if my code is really suitable to avoid misusage.
> 
> Best regards,
> Thomas

  reply index

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-19 22:47 Federico Vaga
2020-06-19 23:31 ` Dave Jiang
2020-06-21  7:24   ` Vinod Koul
2020-06-21 20:36     ` Federico Vaga
2020-06-21 20:45       ` Richard Weinberger
2020-06-21 22:32         ` Federico Vaga
2020-06-22  4:47       ` Vinod Koul
2020-06-22  6:57         ` Federico Vaga
2020-06-22 12:01         ` Thomas Ruf
2020-06-22 12:27           ` Richard Weinberger
2020-06-22 14:01             ` Thomas Ruf
2020-06-22 12:30           ` Federico Vaga
2020-06-22 14:03             ` Thomas Ruf
2020-06-22 15:54           ` Vinod Koul
2020-06-22 16:34             ` Thomas Ruf
2020-06-24  9:30               ` Thomas Ruf
2020-06-24  9:38                 ` Vinod Koul
2020-06-24 12:07                   ` Peter Ujfalusi
2020-06-24 13:58                     ` Thomas Ruf
2020-06-26 10:29                       ` Peter Ujfalusi
2020-06-29 15:18                         ` Thomas Ruf
2020-06-30 12:31                           ` Peter Ujfalusi
2020-07-01 16:13                             ` Thomas Ruf
2020-06-25  0:42     ` Dave Jiang
2020-06-25  8:11       ` Thomas Ruf
2020-06-26 20:08         ` Ira Weiny [this message]
2020-06-29 15:31           ` Thomas Ruf
2020-06-22  9:25 ` Federico Vaga
2020-06-22  9:42   ` Vinod Koul

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