title: Vulkan validation warning catch-22 about VK_KHR_portability_subset on MoltenVK
body: <p>I'm using Vulkan 1.2.170 with MoltenVK (and GLFW) on Big Sur (mid 2014 15&quot; Retina). I created the instance with <code>VK_LAYER_KHRONOS_validation</code> and when I call <code>vkCreateDevice</code> I get the warning</p>
  <pre><code>VUID-VkDeviceCreateInfo-pProperties-04451(ERROR / SPEC): msgNum: 976972960 - Validation Error:
   [ VUID-VkDeviceCreateInfo-pProperties-04451 ] Object 0: handle = 0x10cfaad00, 
  type = VK_OBJECT_TYPE_PHYSICAL_DEVICE; | MessageID = 0x3a3b6ca0 | vkCreateDevice: 
  VK_KHR_portability_subset must be enabled because physical device VkPhysicalDevice 0x10cfaad00[] 
  supports it The Vulkan spec states: If the [VK_KHR_portability_subset] extension is included in 
  pProperties of vkEnumerateDeviceExtensionProperties, ppEnabledExtensions must include 
  &quot;VK_KHR_portability_subset&quot;.
  </code></pre>
  <p>Okay, fine, I add it to the extensions parameter as the only extension. Then it says</p>
  <pre><code>Missing extension required by the device extension VK_KHR_portability_subset:
  VK_KHR_get_physical_device_properties2.
  </code></pre>
  <p>and segfaults. If I add <code>VK_KHR_get_physical_device_properties2</code>, it crashes saying it doesn't exist, which is true (<code>vkEnumerateDeviceExtensionProperties</code> doesn't return it).</p>
  <p>Is this a bug or is there some set of extensions it will accept?</p>
  <p>If it helps, the supported extensions are</p>
  <blockquote>
  <p>VK_KHR_16bit_storage VK_KHR_8bit_storage VK_KHR_bind_memory2 VK_KHR_create_renderpass2 VK_KHR_dedicated_allocation VK_KHR_depth_stencil_resolve VK_KHR_descriptor_update_template VK_KHR_device_group VK_KHR_driver_properties VK_KHR_external_fence VK_KHR_external_memory VK_KHR_external_semaphore VK_KHR_get_memory_requirements2 VK_KHR_image_format_list VK_KHR_maintenance1 VK_KHR_maintenance2 VK_KHR_maintenance3 VK_KHR_multiview VK_KHR_portability_subset VK_KHR_push_descriptor VK_KHR_relaxed_block_layout VK_KHR_sampler_mirror_clamp_to_edge VK_KHR_sampler_ycbcr_conversion VK_KHR_shader_draw_parameters VK_KHR_shader_float16_int8 VK_KHR_storage_buffer_storage_class VK_KHR_swapchain VK_KHR_swapchain_mutable_format VK_KHR_timeline_semaphore VK_KHR_uniform_buffer_standard_layout VK_KHR_variable_pointers VK_EXT_debug_marker VK_EXT_descriptor_indexing VK_EXT_fragment_shader_interlock VK_EXT_hdr_metadata VK_EXT_host_query_reset VK_EXT_image_robustness VK_EXT_inline_uniform_block VK_EXT_memory_budget VK_EXT_private_data VK_EXT_robustness2 VK_EXT_scalar_block_layout VK_EXT_shader_viewport_index_layer VK_EXT_subgroup_size_control VK_EXT_texel_buffer_alignment VK_EXT_vertex_attribute_divisor VK_AMD_gpu_shader_half_float VK_AMD_negative_viewport_height VK_AMD_shader_trinary_minmax VK_INTEL_shader_integer_functions2 VK_GOOGLE_display_timing VK_NV_glsl_shader</p>
  </blockquote>