Gentoo Archives: gentoo-amd64

From: Duncan <1i5t5.duncan@×××.net>
To: gentoo-amd64@l.g.o
Subject: [gentoo-amd64] Re: Heads Up Kernel-3.11 Nvidia-drivers
Date: Wed, 04 Sep 2013 06:02:15
Message-Id: pan$acf62$e57122f8$444abeaf$
1 Mark Knecht posted on Tue, 03 Sep 2013 13:25:15 -0700 as excerpted:
3 > I suspect I can disassociate the CUDA stuff if I have to. I don't have
4 > to tell X11 that the 465 is in the machine, and I have 3 PCI Express
5 > slots so I could potentially have 2 VGAs and 1 CUDA. (I think...)
7 There's actually some brand new developments in that regard -- hit the
8 Linux news in the last week, and scheduled for 3.12.
10 So what's the big deal? They're splitting the formerly single-device KMS/
11 DRM into two separate devices, one of which will be render/compute-only,
12 and thus require lower privs -- classic Unix user/group file permissions,
13 not the root or CAP_SYS_ADMIN that the current device requires, and a
14 second that will be mode-setting/display-controller only, accessible via
15 clone from the current DRM-control node (which is currently unused).
16 Because no new resources are created -- they're simply cloned from the
17 existing control node, required privs here can be reduced as well. The
18 practical effect of the latter will be another step toward allowing user-
19 priv-only X (and wayland).
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31 2 Comments
33 ome ways, as it means any app running as a user/group with suitable file
34 permissions will be able to open compute nodes, no root or CAP_SYS_ADMIN
35 required. That will in turn dramatically open up the possibilities for
36 "ordinary application" use of compute-nodes, thus allowing pretty much
37 any app to use those resources, instead of forcing the severe privilege
38 restrictions currently needed to avoid huge security issues, currently.
40 So why is all this happening now? It turns out that while on x86/amd64,
41 it has historically been the same hardware device handling both rendering
42 and mode-setting, on arm, which is where the big money is now since
43 that's what all the mobile devices seem to run on, these functions are
44 often split into two different pieces of hardware. The existing unified
45 setup could be made to work, but it wasn't a particularly good fit, while
46 the new setup is a natural fit.
48 Meanwhile, while they could have solved their own little hardware problem
49 in their corner of the computing world in just their own drivers, the
50 bigger solution was to split the functionality up in general, thus
51 allowing solutions to a bunch of thorny problems with the existing
52 unified hardware as well. =:^) In addition to the security and compute
53 resource availability issues mentioned above that this solves, it also
54 makes solving problems such as the newer embedded/dedicated gpu pairing
55 on laptops, with the display only attached to the embedded, thus making
56 the dedicated card that's supposed to activate for games and stuff
57 useless, under the current unified setup. Similarly, it'll now be
58 possible to run different user X sessions on different displays driven by
59 the same GPU hardware -- multi-seat-on- single-gpu-multi-display, which
60 currently isn't possible, because only one app can be DRM-master on a gpu
61 at once, and that app must be run by one user, it can't be shared.
63 So the separate render/modeset hardware on arm is driving better and far
64 more flexible solutions for (normally) unified render/modeset hardware on
65 x86/amd64, too! =:^)
67 Original blog announcement:
70 nodes/
72 Initial LWN coverage. (Not much there besides the single paragraph
73 pointer to the above at present, but kernel devs often comment there, and
74 LWN will very likely have a feature article covering it in some depth in
75 one of its coming weekly editions, too.)
79 Phoronix (pre-blog announcement coverage):
83 (earlier...)
87 (earlier still, July...)
91 --
92 Duncan - List replies preferred. No HTML msgs.
93 "Every nonfree program has a lord, a master --
94 and if you use the program, he is your master." Richard Stallman


Subject Author
Re: [gentoo-amd64] Re: Heads Up Kernel-3.11 Nvidia-drivers Marc Joliet <marcec@×××.de>