In short - we want to enforce alignment == 0 for gen4+ GEM object
settings.
Before we merge this we need to inspect all UMD we expect can use
this. My investigation was narrowed to UMD code:
1. IGT
2. Mesa
3. Media-Driver
4. NEO
5. libdrm
6. xf86-intel-video
I would like to ask subsystem developers / maintainers to confirm
my analysis.
1. IGT:
We've already removed / fixed most of the code where alignment != 0.
What left was few multi-card subtests I'm not able to rewrite due
to lack of such hw (nv + intel on the board).
2. Mesa:
gallium/drivers/iris/iris_batch.c,iris_bufmgr.c - it uses softpinning
only with alignment handled by allocator, so drm_i915_gem_exec_object2
alignment field == 0.
drivers/dri/i965/brw_batch.c,brw_screen.c - it uses relocations but
it is supported by allocator, there're no direct alignment settings
to value != 0.
vulcan/anv_batch_chain.c: drm_i915_gem_exec_object2 objects are
initialized within anv_execbuf_add_bo() and .alignment field
is set to 0 there. There's no other place where I've found vulcan
driver touches it both for softpinning / relocations.
3. Media-Driver:
It contains modified libdrm code and three functions which do
allocations, all of them uses mos_gem_bo_alloc_internal():
- mos_gem_bo_alloc() - internally uses alignment == 0, that's ok
- mos_gem_bo_alloc_tiled() - same as mos_gem_bo_alloc()
- mos_gem_bo_alloc_for_render() - this one passes alignment from
the caller and it may be != 0. But I haven't found practical
usage of this function externally (using mos_bo_alloc_for_render()
wrapper).
There's another userptr allocation function: mos_bo_alloc_userptr()
but it doesn't use alignment.
4. NEO:
Uses softpinning only with alignment == 0:
source/os_interface/linux/drm_buffer_object.cpp:
void BufferObject::fillExecObject() has execObject.alignment = 0;
5. libdrm:
Corresponding functions to Media-Driver:
drm_intel_bo_alloc(), drm_intel_bo_alloc_for_render(),
drm_intel_bo_alloc_userptr() and drm_intel_bo_alloc_tiled().
Alignment field is used in drm_intel_bo_alloc_for_render()
so couple not rewritten IGTs may encounter issue here (alignment
passed in IGTs which still uses libdrm == 4096).
6. xf86-intel-video:
src/sna/kgem.c: _kgem_submit() - alignment is set to 0 so this
shouldn't be a problem.
Cc: Petri Latvala <[email protected]>
Cc: Jason Ekstrand <[email protected]>
Cc: Dmitry Rogozhkin <[email protected]>
Cc: Michal Mrozek <[email protected]>
Cc: José Roberto de Souza <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: Daniel Vetter <[email protected]>
Zbigniew Kempczyński (1):
i915/gem/i915_gem_execbuffer: Disallow passing alignment
drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 11 +++++++++++
1 file changed, 11 insertions(+)
--
2.26.0
