drm/i915/stolen: consider I915_BO_ALLOC_GPU_ONLY

Keep the behaviour consistent with normal lmem, where we assume CPU
access if by default required.
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220315181425.576828-3-matthew.auld@intel.com

drivers/gpu/drm/i915/gem/i915_gem_stolen.c

@@ -695,6 +695,14 @@ static int _i915_gem_object_stolen_init(struct intel_memory_region *mem,
 	if (size == 0)
 		return -EINVAL;
 
+	/*
+	 * With discrete devices, where we lack a mappable aperture there is no
+	 * possible way to ever access this memory on the CPU side.
+	 */
+	if (mem->type == INTEL_MEMORY_STOLEN_LOCAL && !mem->io_size &&
+	    !(flags & I915_BO_ALLOC_GPU_ONLY))
+		return -ENOSPC;
+
 	stolen = kzalloc(sizeof(*stolen), GFP_KERNEL);
 	if (!stolen)
 		return -ENOMEM;