drm/i915: add I915_BO_ALLOC_GPU_ONLY

If the user doesn't require CPU access for the buffer, then
ALLOC_GPU_ONLY should be used, in order to prioritise allocating in the
non-mappable portion of LMEM, on devices with small BAR.

v2(Thomas):
  - The BO_ALLOC_TOPDOWN naming here is poor, since this is pure lies on
    systems that don't even have small BAR. A better name is GPU_ONLY,
    which is accurate regardless of the configuration.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Acked-by: Nirmoy Das <nirmoy.das@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220225145502.331818-3-matthew.auld@intel.com

4 files changed, 30 insertions, 8 deletions

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
index 0098a32490f0..fd54eb8f4826 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
@@ -319,16 +319,23 @@ struct drm_i915_gem_object {
 #define I915_BO_ALLOC_PM_VOLATILE BIT(4)
 /* Object needs to be restored early using memcpy during resume */
 #define I915_BO_ALLOC_PM_EARLY    BIT(5)
+/*
+ * Object is likely never accessed by the CPU. This will prioritise the BO to be
+ * allocated in the non-mappable portion of lmem. This is merely a hint, and if
+ * dealing with userspace objects the CPU fault handler is free to ignore this.
+ */
+#define I915_BO_ALLOC_GPU_ONLY	  BIT(6)
 #define I915_BO_ALLOC_FLAGS (I915_BO_ALLOC_CONTIGUOUS | \
 			     I915_BO_ALLOC_VOLATILE | \
 			     I915_BO_ALLOC_CPU_CLEAR | \
 			     I915_BO_ALLOC_USER | \
 			     I915_BO_ALLOC_PM_VOLATILE | \
-			     I915_BO_ALLOC_PM_EARLY)
-#define I915_BO_READONLY          BIT(6)
-#define I915_TILING_QUIRK_BIT     7 /* unknown swizzling; do not release! */
-#define I915_BO_PROTECTED         BIT(8)
-#define I915_BO_WAS_BOUND_BIT     9
+			     I915_BO_ALLOC_PM_EARLY | \
+			     I915_BO_ALLOC_GPU_ONLY)
+#define I915_BO_READONLY          BIT(7)
+#define I915_TILING_QUIRK_BIT     8 /* unknown swizzling; do not release! */
+#define I915_BO_PROTECTED         BIT(9)
+#define I915_BO_WAS_BOUND_BIT     10
 	/**
 	 * @mem_flags - Mutable placement-related flags
 	 *
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
index 183b861620b8..97c820eee115 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
@@ -358,6 +358,9 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
 	    !i915_gem_object_has_iomem(obj))
 		return ERR_PTR(-ENXIO);
 
+	if (WARN_ON_ONCE(obj->flags & I915_BO_ALLOC_GPU_ONLY))
+		return ERR_PTR(-EINVAL);
+
 	assert_object_held(obj);
 
 	pinned = !(type & I915_MAP_OVERRIDE);
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_region.c b/drivers/gpu/drm/i915/gem/i915_gem_region.c
index 6d65c5849874..6cf94469d5a8 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_region.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_region.c
@@ -45,6 +45,11 @@ i915_gem_object_create_region(struct intel_memory_region *mem,
 
 	GEM_BUG_ON(flags & ~I915_BO_ALLOC_FLAGS);
 
+	if (WARN_ON_ONCE(flags & I915_BO_ALLOC_GPU_ONLY &&
+			 (flags & I915_BO_ALLOC_CPU_CLEAR ||
+			  flags & I915_BO_ALLOC_PM_EARLY)))
+		return ERR_PTR(-EINVAL);
+
 	if (!mem)
 		return ERR_PTR(-ENODEV);
 
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
index 0363987dee97..a13e0204a139 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
@@ -129,10 +129,14 @@ i915_ttm_place_from_region(const struct intel_memory_region *mr,
 	place->mem_type = intel_region_to_ttm_type(mr);
 
 	if (flags & I915_BO_ALLOC_CONTIGUOUS)
-		place->flags = TTM_PL_FLAG_CONTIGUOUS;
+		place->flags |= TTM_PL_FLAG_CONTIGUOUS;
 	if (mr->io_size && mr->io_size < mr->total) {
-		place->fpfn = 0;
-		place->lpfn = mr->io_size >> PAGE_SHIFT;
+		if (flags & I915_BO_ALLOC_GPU_ONLY) {
+			place->flags |= TTM_PL_FLAG_TOPDOWN;
+		} else {
+			place->fpfn = 0;
+			place->lpfn = mr->io_size >> PAGE_SHIFT;
+		}
 	}
 }
 
@@ -890,6 +894,9 @@ static vm_fault_t vm_fault_ttm(struct vm_fault *vmf)
 	if (!obj)
 		return VM_FAULT_SIGBUS;
 
+	if (obj->flags & I915_BO_ALLOC_GPU_ONLY)
+		return -EINVAL;
+
 	/* Sanity check that we allow writing into this object */
 	if (unlikely(i915_gem_object_is_readonly(obj) &&
 		     area->vm_flags & VM_WRITE))