icd: Disable underlying Vulkan implicit layers by default

Author: aqnuep

icd/icd_env_helper.cpp

@@ -8,6 +8,7 @@
 #include "icd_env_helper.h"
 
 #include <stdlib.h>
+#include <string.h>
 #include <sstream>
 
 #ifdef _WIN32
@@ -123,6 +124,13 @@ const std::unordered_map<const char*, std::string> EnvironmentHelper::InitLayere
         auto env_var_value = getenv(layered_env_var.c_str());
         if (env_var_value != nullptr) {
             layered_envs.emplace(loader_env_var, env_var_value);
+        } else if (strcmp(loader_env_var, "VK_LOADER_LAYERS_DISABLE") == 0) {
+            // NOTE: We disable Vulkan implicit layers unless otherwise instructed by the environment
+            // as none of the device select / switchable graphics / optimus layers operate correctly
+            // in most non-trivial environments, and it is anyway questionable whether we want any
+            // Vulkan implicit layers to take effect when running Vulkan SC applications against the
+            // emulation driver stack.
+            layered_envs.emplace("VK_LOADER_LAYERS_DISABLE", "~implicit~");
         }
     }
     return layered_envs;

tests/icd/test_infrastructure.cpp

@@ -44,6 +44,11 @@ TEST_F(InfrastructureTest, EnvironmentVariables) {
         auto value = getenv(env_var_name.c_str());
         if (value == nullptr) {
             env_vars[env_var_name] = "";
+
+            // Expect that the Emulation ICD will disable all Vulkan implicit layers by default
+            if (env_var_name == "VK_LOADER_LAYERS_DISABLE") {
+                env_vars[env_var_name] = "~implicit~";
+            }
         } else {
             env_vars[env_var_name] = value;
         }
@@ -72,7 +77,7 @@ TEST_F(InfrastructureTest, EnvironmentVariables) {
                 if (value == nullptr) {
                     value = "";
                 }
-                EXPECT_STREQ(env_vars[vksc_emu_env_var_name].c_str(), value) << env_var_name << " has incorrect value";
+                EXPECT_STREQ(env_vars[env_var_name].c_str(), value) << env_var_name << " has incorrect value";
 
                 // Expect VKSC_EMU_VK_* to also have the value of VKSC_EMU_VK_*
                 const char* vksc_emu_value = getenv(vksc_emu_env_var_name.c_str());