linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Jason Gunthorpe <jgg@nvidia.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Oded Gabbay <oded.gabbay@gmail.com>,
	Dave Airlie <airlied@gmail.com>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	Yuji Ishikawa <yuji2.ishikawa@toshiba.co.jp>,
	Jiho Chu <jiho.chu@samsung.com>, Arnd Bergmann <arnd@arndb.de>,
	"Linux-Kernel@Vger. Kernel. Org" <linux-kernel@vger.kernel.org>
Subject: Re: New subsystem for acceleration devices
Date: Mon, 8 Aug 2022 14:55:28 -0300	[thread overview]
Message-ID: <YvFOEPdC9r8QBH11@nvidia.com> (raw)
In-Reply-To: <YvCozvgodIY19LSr@kroah.com>

On Mon, Aug 08, 2022 at 08:10:22AM +0200, Greg Kroah-Hartman wrote:
> On Sun, Aug 07, 2022 at 02:25:33PM +0300, Oded Gabbay wrote:
> > 2. Common code to handle drivers that want to allow a single user at a
> > time to run open the device char file.
> 
> Note, that's an impossible request, and one that the kernel should never
> worry about, so don't even try it.  Think about userspace doing an call
> to dup() on an open char file descriptor and then passing that off
> somewhere else.

Oded is talking about a model like VFIO has where the HW has a limited
number of concurrent state registers - lets say in this case the ASID
translation mapping the accelerator into DMA.

Each 'struct file' that is created owns one of those HW state
registers, and each struct file is completely isolated from all
others. eg someone controlling the accelerator through struct file A
cannot access memory mapped into the accelerator through struct file
B.

So, the number of struct files that can be created is capped at the
number of HW state registers the device can support (eg one for
Habana).

This is different from the number of FDs pointing at the struct file.
Userpsace can open a HW state and point a lot of FDs at it, that is
userspace's problem. From a kernel view they all share one struct file
and thus one HW state.

Jason

  reply	other threads:[~2022-08-08 17:55 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20220731114605epcas1p1afff6b948f542e2062b60d49a8023f6f@epcas1p1.samsung.com>
2022-07-31 11:45 ` New subsystem for acceleration devices Oded Gabbay
2022-07-31 15:37   ` Greg Kroah-Hartman
2022-08-01  2:29     ` yuji2.ishikawa
2022-08-01  8:21       ` Oded Gabbay
2022-08-03  4:39         ` yuji2.ishikawa
2022-08-03  5:34           ` Greg KH
2022-08-03 20:28           ` Oded Gabbay
2022-08-02 17:25   ` Jiho Chu
2022-08-02 19:07     ` Oded Gabbay
2022-08-03 19:04   ` Dave Airlie
2022-08-03 20:20     ` Oded Gabbay
2022-08-03 23:31       ` Daniel Stone
2022-08-04  6:46         ` Oded Gabbay
2022-08-04  9:27           ` Jiho Chu
2022-08-03 23:54       ` Dave Airlie
2022-08-04  7:43         ` Oded Gabbay
2022-08-04 14:50           ` Jason Gunthorpe
2022-08-04 17:48             ` Oded Gabbay
2022-08-05  0:22               ` Jason Gunthorpe
2022-08-07  6:43                 ` Oded Gabbay
2022-08-07 11:25                   ` Oded Gabbay
2022-08-08  6:10                     ` Greg Kroah-Hartman
2022-08-08 17:55                       ` Jason Gunthorpe [this message]
2022-08-09  6:23                         ` Greg Kroah-Hartman
2022-08-09  8:04                           ` Christoph Hellwig
2022-08-09  8:32                             ` Arnd Bergmann
2022-08-09 12:18                               ` Jason Gunthorpe
2022-08-09 12:46                                 ` Arnd Bergmann
2022-08-09 14:22                                   ` Jason Gunthorpe
2022-08-09  8:45                             ` Greg Kroah-Hartman
2022-08-08 17:46                   ` Jason Gunthorpe
2022-08-08 20:26                     ` Oded Gabbay
2022-08-09 12:43                       ` Jason Gunthorpe
2022-08-05  3:02           ` Dave Airlie
2022-08-07  6:50             ` Oded Gabbay
2022-08-09 21:42               ` Oded Gabbay
2022-08-10  9:00                 ` Jiho Chu
2022-08-10 14:05                 ` yuji2.ishikawa
2022-08-10 14:37                   ` Oded Gabbay
2022-08-23 18:23                 ` Kevin Hilman
2022-08-23 20:45                   ` Oded Gabbay
2022-08-29 20:54                     ` Kevin Hilman
2022-09-23 16:21                       ` Oded Gabbay
2022-09-26  8:16                         ` Christoph Hellwig
2022-09-29  6:50                           ` Oded Gabbay
2022-08-04 12:00         ` Tvrtko Ursulin
2022-08-04 15:03           ` Jeffrey Hugo
2022-08-04 17:53             ` Oded Gabbay

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=YvFOEPdC9r8QBH11@nvidia.com \
    --to=jgg@nvidia.com \
    --cc=airlied@gmail.com \
    --cc=arnd@arndb.de \
    --cc=dri-devel@lists.freedesktop.org \
    --cc=gregkh@linuxfoundation.org \
    --cc=jiho.chu@samsung.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=oded.gabbay@gmail.com \
    --cc=yuji2.ishikawa@toshiba.co.jp \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).