On 08/13/2018 02:28 PM, Thomas Zimmermann wrote:
Hi
Am 13.08.2018 um 12:33 schrieb Christian König:
Yes, please! I had it on my TODO list to clean that up for an eternity.
On top of these patches, I have a patch set that provides a single
init/release interface for TTM global data. I'll post it when the
current patches got some feed back.
I'd really like to move the code from drm_global.c back into TTM. It's
TTM-specific and not useful elsewhere. However, the first commit message
from 2010 [1] says that some unnamed, external driver uses this code for
something. Do you know if this still applies?
I'm not sure actually, and not even sure that external driver ever
intended to be compatible with upcoming upstream versions of drm. In
that case I guess whoever maintains it should speak up now...
The drm global stuff was added to facilitate for subsystems that wanted
to register stuff that was really system-global and not per-device, and
also not used by all drivers. As an example, even if the memory
accounting is currently restricted to TTM, IMO we probably want
something drm global to avoid malicious user-space app consuming all
kernel memory by, for example, repeatedly open gem handles until kernel
memory is exhausted. TTM drivers should stop that, but it's pretty
meaningless if they share the system with a non-TTM driver that
considers this "stupid and difficult".
So having said that, I'm not really against ditching the drm_global
stuff since it hasn't found any out-of-ttm usage.
/Thomas
Best regards
Thomas
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ba4420c224c2808f2661cf8428f43ceef7a73a4a
Actually I never understood why that should be driver work to setup TTM?
I mean can't we just have a module_init/module_exit for TTM?
Thanks,
Christian.
Am 13.08.2018 um 12:24 schrieb Thomas Zimmermann:
TTM uses global memory and BO for backing graphics buffers. These are
represented by struct ttm_mem_global and struct ttm_bo_global.
Currently, struct ttm_bo_global can only be initialized and released
through
struct ttm_bo_global_ref. This is a workaround for passing an instance of
ttm_mem_global to the BO global initialization code.
The use of struct ttm_bo_global_ref makes driver code unnecessary hard to
understand. At the same time drivers can use any combination of memory
and
BO for initializing the global instances. This can result in subtle bugs
when the order of initializing and releasing drivers changes.
As a first step for resolving these problems, the provided patch set
separates initialization and release of struct ttm_bo_global from
struct ttm_bo_global_ref.
The first patch only renames ttm_bo_global_{init/release}. Hopefully this
change can be applied at once for all drivers.
Future directions: All TTM-based drivers follow the same pattern for
setting
up the TTM. In a follow-up patch, this code can be moved into a single
place
and shared among drivers.
Thomas Zimmermann (2):
drm/ttm: Rename ttm_bo_global_{init,release}() to
ttm_bo_global_ref_*()
drm/ttm: Provide ttm_bo_global_{init/release}() for struct
ttm_bo_global
drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 4 +-
drivers/gpu/drm/ast/ast_ttm.c | 4 +-
drivers/gpu/drm/bochs/bochs_mm.c | 4 +-
drivers/gpu/drm/cirrus/cirrus_ttm.c | 4 +-
drivers/gpu/drm/hisilicon/hibmc/hibmc_ttm.c | 4 +-
drivers/gpu/drm/mgag200/mgag200_ttm.c | 4 +-
drivers/gpu/drm/nouveau/nouveau_ttm.c | 4 +-
drivers/gpu/drm/qxl/qxl_ttm.c | 4 +-
drivers/gpu/drm/radeon/radeon_ttm.c | 4 +-
drivers/gpu/drm/ttm/ttm_bo.c | 12 ++---
drivers/gpu/drm/virtio/virtgpu_ttm.c | 4 +-
drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c | 4 +-
drivers/staging/vboxvideo/vbox_ttm.c | 4 +-
include/drm/ttm/ttm_bo_driver.h | 53 ++++++++++++++++-----
14 files changed, 70 insertions(+), 43 deletions(-)
--
2.18.0
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