On small BAR configurations, when dealing with I915_MEMORY_CLASS_DEVICE allocations, we assume that by default, all userspace allocations should be placed in the non-CPU visible portion. Note that dumb buffers are not included here, since these are not "GPU accelerated" and likely need CPU access. We choose to just always set GPU_ONLY, and let the backend figure out if that should be ignored or not, for example on full BAR systems.
In a later patch userspace will be able to provide a hint if CPU access to the buffer is needed.
v2(Thomas) - Apply GPU_ONLY on all discrete devices, but only if the BO can be placed in LMEM. Down in the depths this should be turned into a noop, where required, and as an annotation it still make some sense. If we apply it regardless of the placements then we end up needing to check the placements during exec capture. Also it's slightly inconsistent since the NEEDS_CPU_ACCESS can only be applied on objects that can be placed in LMEM. The other annoyance would be gem_create_ext vs plain gem_create, if we were to always apply GPU_ONLY.
Testcase: igt@gem-create@create-ext-cpu-access-sanity-check Testcase: igt@gem-create@create-ext-cpu-access-big Signed-off-by: Matthew Auld matthew.auld@intel.com Cc: Thomas Hellström thomas.hellstrom@linux.intel.com Cc: Lionel Landwerlin lionel.g.landwerlin@intel.com Cc: Tvrtko Ursulin tvrtko.ursulin@linux.intel.com Cc: Jon Bloomfield jon.bloomfield@intel.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Jordan Justen jordan.l.justen@intel.com Cc: Kenneth Graunke kenneth@whitecape.org Cc: Akeem G Abodunrin akeem.g.abodunrin@intel.com Reviewed-by: Thomas Hellström thomas.hellstrom@linux.intel.com --- drivers/gpu/drm/i915/gem/i915_gem_create.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_create.c b/drivers/gpu/drm/i915/gem/i915_gem_create.c index 5802692ea604..d094cae0ddf1 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_create.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_create.c @@ -427,6 +427,14 @@ i915_gem_create_ext_ioctl(struct drm_device *dev, void *data, ext_data.n_placements = 1; }
+ /* + * TODO: add a userspace hint to force CPU_ACCESS for the object, which + * can override this. + */ + if (ext_data.n_placements > 1 || + ext_data.placements[0]->type != INTEL_MEMORY_SYSTEM) + ext_data.flags |= I915_BO_ALLOC_GPU_ONLY; + obj = __i915_gem_object_create_user_ext(i915, args->size, ext_data.placements, ext_data.n_placements,