[Devel] dev_ns: tips needed

[Sergey Korshunoff]

Hello, openvz developers!

I'm interested in framebuffer vritualization for openvz (2.6.32 and 3.10).
Such thing was developed in CELLS project
http://systems.cs.columbia.edu/projects/cells/

There was some work done in Paralles
http://habrahabr.ru/company/parallels/blog/174211/

Some tips are needed regarding dev_ns. Is this ns already present in openvz?

PS: cells kernel is based on linux 3.1.0

Commit Message
========================
dev_ns: adopt the framebuffer subsystem
Adds device namespace logic to the framebuffer subsystem.

Isolate framebuffer state between device namespaces, and multiplex access
to hardware state between the virtual framebuffers.

Associate with each device namespace a shadow, virtual 'struct fb_info'
(vinfo) and a backing buffer, for each registered hardware framebuffer.
Access from an active (foreground) device namespace is passed-through
directly to the underlying device. Access from a passive (background)
device namespace is directed to the virtal fb_info.

The backing buffer is used for mmap-ed memory in passive namespace, so
any drawing occurs to the backing buffer instead of to the real driver.
When the active namespace changes, perform a context-switch and swap
such mappings: remap memory previously in foreground to the backing
buffer, and from background to the underlying device. The contents of
the framebuffer is saved and restored in (from) the bacgkround (active)
backing buffer, respectively.

Changelog:
[16-Aug-13] v1 - initial version
Change-Id: I355650abc45b6f0c6c66fd86f91e3cfd8e50b4f7
Signed-off-by: Oren Laadan <orenl at cellrox.com>
========================
+config FB_DEV_NS
75	+»       bool "Enable FB device namespace"
76	+»       depends on FB
77	+»       depends on DEV_NS
78	+»       select FB_SYS_FOPS
79	+»       select FB_CFB_FILLRECT
80	+»       select FB_CFB_COPYAREA
81	+»       select FB_CFB_IMAGEBLIT
82	+»       default n
83	+»       ---help---
84	+»        Allow per-namespace virtual framebuffers by mulplexing access to
85	+»        the hardware framebuffer. This is intended for containers with
86	+»        device namespace (see COFNIG_DEV_NS) interactive use case, where
87	+»        there is a single "foreground" container and possibly multiple
88	+»        "background" containers.
89	+
90	+»        It provdies virtualization for the framebuffer subsystem. When
91	+»        activated, each container has a private view of the framebuffer,
92	+»        but only the foreground container has pass-through access to the
93	+»        hardware framebuffer, while the others see a virtual framebuffer.
94	+
95	+»        If unsure, say N.
========
dev_ns: introduce device namespaces
Introduce device namespaces:

The idea with a device namespace comes from the Android-Cells project where
namespaces are utilized to create a container-like environment on Linux, only
where there's a notion of an 'active' namespace and all other namespaces are
inactive. In such a case only processes residing within the active device
namespace should communicate with actual devices, where processes inside
inactive containers should be able to communicate gracefully with the device
driver, but not the device.

Changelog:
[16-Aug-2013] v1 - initial version

Change-Id: I143a84272e230089f7e5db58d02fb9b1f2df9ee1
Signed-off-by: Oren Laadan <orenl at cellrox.com>
Signed-off-by: Amir Goldstein <amir at cellrox.com>
==============
+config DEV_NS
854	+»       bool "Device Namespaces (EXPERIMENTAL)"
855	+»       default n
856	+»       depends on PID_NS
857	+»       help
858	+»       Support device driver namespaces. This allows drivers to multiplex
859	+»       access to its physical or logical resources. A device namespace has
860	+»       a one-to-one relationship with a PID namespace currentlly, but this
861	+»       will likely change in the future.
=============