Run the same-device Vulkan OpenXR backend on desktop Linux

Lepton's Vulkan driver has no external memory or sync fd extensions, so the Steam Frame gets a native SteamOS build instead. Its backend is the PC's: OpenXR creates Dawn's own Vulkan instance and device, and the eyes are copied into the swapchain on Dawn's queue, with nothing shared between devices. - openxr_vulkan_win32 and Aurora's vulkan_win32_interop now compile on desktop Linux. Dawn links statically there, so the bridge calls the patched package's hooks directly, and exists only when the package's aurora-dawn.json declares the Vulkan hook ABI (AuroraDawnProvider turns AuroraVulkanAbi into AURORA_DAWN_VULKAN_HOOKS); a stock Dawn keeps the stubs and VR falls back to the desktop. - openxr_integration.cpp gains a Linux branch: XR_KHR_vulkan_enable2, the timespec clock, refresh rate, performance level, the Frame controllers and eye gaze; fragment density maps are requested on Linux as on the Quest (fdm.cpp and gpu.cpp, AURORA_FDM=0/1 overrides). - Controller motion uses XR_KHR_convert_timespec_time on any Linux. - CMake: Vulkan headers are fetched for Linux OpenXR builds, the headset option is MKW_HEADSET on Android and Linux, and Linux aarch64 builds take MKW_LINUX_CPU (cortex-x4 for the Steam Frame, else native). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_019HBRGKTE1GnN2ah8gcZKr3
2026-10-04 22:00:08 +02:00 · 2026-10-04 09:48:48 +00:00
1 parent da0d13bdd2
commit 28a25108c6
@@ -187,7 +187,7 @@ android {
        }
        // Valve's Steam Frame, through Lepton (SteamOS's Android layer) and SteamVR's Android
        // OpenXR runtime. Its manifest (src/steamFrame) drops the Horizon OS entries, and
-        // MKW_ANDROID_HEADSET gives the runtime the Frame's defaults (runtime_config.h).
+        // MKW_HEADSET gives the runtime the Frame's defaults (runtime_config.h).
        create("steamFrame") {
            dimension = "headset"
            // Horizon OS only; src/steamFrame/AndroidManifest.xml removes the entry.
@@ -199,7 +199,7 @@ android {
                cmake {
                    arguments += listOf(
                        "-DMKW_ANDROID_CPU=${headsetCpus.getValue("steamFrame")}",
-                        "-DMKW_ANDROID_HEADSET=steam_frame",
+                        "-DMKW_HEADSET=steam_frame",
                    )
                }
            }
@@ -268,7 +268,10 @@ elseif (_aurora_dawn_provider STREQUAL "package")
  # A package built with Aurora's patches (android/Build-QuestDawn.ps1) describes them in
  # aurora-dawn.json. Only such a package has the fragment density map ABI
  # (include/aurora/dawn_fdm_abi.h); aurora_core compiles its callers against it.
+  # The Vulkan hook ABI (include/aurora/dawn_vulkan_abi.h) is the other half: a package built by
+  # Launcher/build-dawn-linux.sh carries it, and the Linux OpenXR backend needs it.
  set(AURORA_DAWN_FDM_ABI 0 PARENT_SCOPE)
+  set(AURORA_DAWN_VULKAN_HOOKS_ABI 0 PARENT_SCOPE)
  if (EXISTS "${_dawn_pkg_dir}/aurora-dawn.json")
    file(READ "${_dawn_pkg_dir}/aurora-dawn.json" _aurora_dawn_manifest)
    string(JSON _aurora_dawn_fdm_abi ERROR_VARIABLE _aurora_dawn_manifest_error
@@ -277,6 +280,12 @@ elseif (_aurora_dawn_provider STREQUAL "package")
      set(AURORA_DAWN_FDM_ABI ${_aurora_dawn_fdm_abi} PARENT_SCOPE)
      message(STATUS "aurora: Dawn package carries the fragment density map ABI ${_aurora_dawn_fdm_abi}")
    endif ()
+    string(JSON _aurora_dawn_vulkan_abi ERROR_VARIABLE _aurora_dawn_manifest_error
+      GET "${_aurora_dawn_manifest}" AuroraVulkanAbi)
+    if (NOT _aurora_dawn_manifest_error AND _aurora_dawn_vulkan_abi GREATER 0)
+      set(AURORA_DAWN_VULKAN_HOOKS_ABI ${_aurora_dawn_vulkan_abi} PARENT_SCOPE)
+      message(STATUS "aurora: Dawn package carries the Vulkan hook ABI ${_aurora_dawn_vulkan_abi}")
+    endif ()
  endif ()

  _aurora_dawn_set_platform_backends()
@@ -39,6 +39,14 @@ if (AURORA_ENABLE_GX)
    # of producing unresolved interop references.
    if (CMAKE_SYSTEM_NAME STREQUAL Windows)
        target_sources(aurora_core PRIVATE lib/webgpu/d3d12_interop.cpp lib/webgpu/vulkan_win32_interop.cpp)
+    elseif (CMAKE_SYSTEM_NAME STREQUAL Linux)
+        # The same-device Vulkan bridge, for the desktop Linux OpenXR backend (SteamOS on the Steam
+        # Frame). Static Dawn on Linux is linked directly, so the bridge is compiled in only against
+        # a package with Aurora's Vulkan hooks; otherwise the file is its C ABI stubs.
+        target_sources(aurora_core PRIVATE lib/webgpu/vulkan_win32_interop.cpp)
+        if (AURORA_DAWN_VULKAN_HOOKS_ABI)
+            target_compile_definitions(aurora_core PRIVATE AURORA_DAWN_VULKAN_HOOKS=${AURORA_DAWN_VULKAN_HOOKS_ABI})
+        endif ()
    endif ()
    # Android/Vulkan counterpart: the AHardwareBuffer stereo bridge. The file
    # compiles to C ABI stubs on every other platform so the runtime's OpenXR
@@ -6,8 +6,10 @@
 #include <algorithm>
 #include <bit>

-// AURORA_DAWN_FDM carries the ABI version of the Dawn package's patches (AuroraDawnProvider.cmake).
-#if defined(__ANDROID__) && defined(AURORA_DAWN_FDM)
+// AURORA_DAWN_FDM carries the ABI version of the Dawn package's patches (AuroraDawnProvider.cmake):
+// the Quest's (android/Build-QuestDawn.ps1) or desktop Linux's (Launcher/build-dawn-linux.sh), both
+// linked statically.
+#if (defined(__ANDROID__) || defined(__linux__)) && defined(AURORA_DAWN_FDM)
 #include <aurora/dawn_fdm_abi.h>
 static_assert(AURORA_DAWN_FDM == AURORA_DAWN_FDM_ABI,
              "The Dawn package's fragment density map ABI does not match include/aurora/dawn_fdm_abi.h");
@@ -53,7 +55,7 @@ void device_created() noexcept {
 #else
  if (g_requested) {
    Log.warn("Fragment density maps: unavailable; this build links a Dawn without Aurora's patches "
-             "(android/Build-QuestDawn.ps1)");
+             "(android/Build-QuestDawn.ps1, Launcher/build-dawn-linux.sh)");
  }
 #endif
 }
@@ -830,6 +830,13 @@ bool initialize(AuroraBackend auroraBackend) {
    const int fdmOverride = android_debug::property_int("debug.wiicompiled.fdm", -1);
    fdm::request(g_backendType == wgpu::BackendType::Vulkan &&
                 (fdmOverride >= 0 ? fdmOverride == 1 : g_config.xrFragmentDensityMap));
+#elif defined(__linux__)
+    // Desktop Linux (SteamOS on the Steam Frame), with a Dawn built by Launcher/build-dawn-linux.sh.
+    // AURORA_FDM=0 or 1 overrides the settings, as debug.wiicompiled.fdm does on the Quest.
+    const char* fdmOverride = std::getenv("AURORA_FDM");
+    fdm::request(g_backendType == wgpu::BackendType::Vulkan &&
+                 (fdmOverride != nullptr && *fdmOverride != '\0' ? std::strcmp(fdmOverride, "1") == 0
+                                                                 : g_config.xrFragmentDensityMap));
 #endif
    const auto future =
        g_adapter.RequestDevice(&deviceDescriptor, wgpu::CallbackMode::WaitAnyOnly,
@@ -4,8 +4,27 @@
 #include "../stereo.hpp"
 #include "../stereo_overlay.hpp"
 #include "gpu.hpp"
-#if defined(_WIN32) && defined(WEBGPU_DAWN) && defined(DAWN_ENABLE_BACKEND_VULKAN)
+// Windows loads the patched webgpu_dawn.dll's exports at run time. Desktop Linux (SteamOS on the
+// Steam Frame) links Dawn statically, so there the bridge exists only against a package built with
+// the hooks (AURORA_DAWN_VULKAN_HOOKS, from its aurora-dawn.json) and calls them directly.
+#if defined(WEBGPU_DAWN) && defined(DAWN_ENABLE_BACKEND_VULKAN) && \
+    (defined(_WIN32) || (defined(__linux__) && !defined(__ANDROID__) && defined(AURORA_DAWN_VULKAN_HOOKS)))
+#if defined(_WIN32)
 #include <windows.h>
+#else
+static_assert(AURORA_DAWN_VULKAN_HOOKS == AURORA_DAWN_VULKAN_ABI,
+              "The Dawn package's Vulkan hook ABI does not match include/aurora/dawn_vulkan_abi.h");
+extern "C" {
+uint32_t AuroraDawnVulkanVersion(void);
+int AuroraDawnVulkanConfigure(const AuroraDawnVulkanHooks* hooks);
+int AuroraDawnVulkanGetHandles(void* device, AuroraDawnVulkanHandles* handles);
+void* AuroraDawnVulkanWrap(void* device, const void* textureDescriptor, uint64_t image);
+int AuroraDawnVulkanRelease(void* device, void* const* textures, uint32_t count);
+void* AuroraDawnVulkanLock(void* device);
+void AuroraDawnVulkanUnlock(void* guard);
+int AuroraDawnVulkanDrain(void* device);
+}
+#endif
 #include <algorithm>
 #include <array>
 #include <memory>
@@ -23,6 +42,17 @@ struct Api {
  AuroraDawnVulkanUnlockFn unlock = nullptr;
  AuroraDawnVulkanDrainFn drain = nullptr;
  bool Load() {
+#if !defined(_WIN32)
+    if (AuroraDawnVulkanVersion() != AURORA_DAWN_VULKAN_ABI) return false;
+    configure = &AuroraDawnVulkanConfigure;
+    handles = &AuroraDawnVulkanGetHandles;
+    wrap = &AuroraDawnVulkanWrap;
+    release = &AuroraDawnVulkanRelease;
+    lock = &AuroraDawnVulkanLock;
+    unlock = &AuroraDawnVulkanUnlock;
+    drain = &AuroraDawnVulkanDrain;
+    return true;
+#else
    HMODULE module = GetModuleHandleW(L"webgpu_dawn.dll");
    if (!module) return false;
    auto version = reinterpret_cast<AuroraDawnVulkanVersionFn>(GetProcAddress(module, "AuroraDawnVulkanVersion"));
@@ -37,6 +67,7 @@ struct Api {
    LOAD(drain, AuroraDawnVulkanDrainFn, "AuroraDawnVulkanDrain");
 #undef LOAD
    return true;
+#endif
  }
 } api;
 int64_t VkFormat(wgpu::TextureFormat format) {
@@ -222,8 +253,9 @@ void* aurora_vulkan_win32_lock_queue() {
 void aurora_vulkan_win32_unlock_queue(void* guard) { aurora::vulkan_win32::api.unlock(guard); }
 #else
 // C ABI stubs keep the runtime's OpenXR integration linkable on Windows GX
-// builds whose Dawn has no Vulkan backend; the backend then reports that the
-// bridge is unavailable and the game falls back to the desktop renderer.
+// builds whose Dawn has no Vulkan backend, and on Linux against a Dawn without
+// Aurora's hooks; the backend then reports that the bridge is unavailable and
+// the game falls back to the desktop renderer.
 bool aurora_vulkan_win32_configure(const AuroraDawnVulkanHooks*) { return false; }
 bool aurora_vulkan_win32_get_handles(AuroraDawnVulkanHandles* handles, int64_t* format) {
  if (handles) *handles = {};
@@ -22,7 +22,7 @@ to a single shared device first.
 | | Quest flavours | `steamFrame` |
 | --- | --- | --- |
 | CPU target (`kit.json` `androidCpu`) | `cortex-a77` (`kryo` on Quest 1) | `cortex-x4` |
-| `MKW_ANDROID_HEADSET` | `quest` | `steam_frame` (defines `MKW_HEADSET_STEAM_FRAME`) |
+| `MKW_HEADSET` | empty | `steam_frame` (defines `MKW_HEADSET_STEAM_FRAME`) |
 | Library entry | `LauncherActivity` (Quest 1: `QuestActivity`) | `FrameEntryActivity` |
 | Horizon OS manifest entries | present | removed |
 | `[vr] refresh_rate` default | `0` (the headset's own) | `120` |
@@ -37,18 +37,19 @@ option(MKW_BUILD_PRODUCTS "Build translated WiiCompiled product targets" ON)
 # aurora-main and its third-party tree stay unaffected.
 set(MKW_PROJECT_COMPILE_DEFINITIONS NOMINMAX)

-# The Android headset family the build is for (the Gradle flavour passes it). The
-# Steam Frame build runs under SteamVR's Android runtime rather than Horizon OS and
-# takes its own defaults (runtime_config.h) through MKW_HEADSET_STEAM_FRAME. The
-# definition reaches every target below, so the game kit's recorded compile flags
-# carry it too.
-if(MKW_PLATFORM_ANDROID)
-    set(MKW_ANDROID_HEADSET "quest" CACHE STRING "Android headset family: quest (Meta Quest, any flavour) or steam_frame")
-    set_property(CACHE MKW_ANDROID_HEADSET PROPERTY STRINGS quest steam_frame)
-    if(MKW_ANDROID_HEADSET STREQUAL "steam_frame")
+# The headset a standalone build is for: the Android app's Gradle flavour passes
+# it, and so does a native SteamOS build for the Steam Frame
+# (Launcher/local-build.sh --headset steam_frame). The Steam Frame takes its own
+# defaults (runtime_config.h) through MKW_HEADSET_STEAM_FRAME. The definition
+# reaches every target below, so the Quest game kit's recorded compile flags carry
+# it too.
+if(MKW_PLATFORM_ANDROID OR MKW_PLATFORM_LINUX)
+    set(MKW_HEADSET "" CACHE STRING "Headset the build targets: empty (a Meta Quest on Android, any PC headset elsewhere) or steam_frame")
+    set_property(CACHE MKW_HEADSET PROPERTY STRINGS "" steam_frame)
+    if(MKW_HEADSET STREQUAL "steam_frame")
        list(APPEND MKW_PROJECT_COMPILE_DEFINITIONS MKW_HEADSET_STEAM_FRAME=1)
-    elseif(NOT MKW_ANDROID_HEADSET STREQUAL "quest")
-        message(FATAL_ERROR "MKW_ANDROID_HEADSET must be quest or steam_frame, not '${MKW_ANDROID_HEADSET}'")
+    elseif(NOT MKW_HEADSET STREQUAL "")
+        message(FATAL_ERROR "MKW_HEADSET must be empty or steam_frame, not '${MKW_HEADSET}'")
    endif()
 endif()

@@ -148,10 +149,10 @@ set(MKW_TRANSLATED_COMPILE_JOBS 0 CACHE STRING
 Scheduling only - never affects output bytes, so it is deliberately outside the canonical flag fingerprint.")
 set(MKW_CPPWINRT_INCLUDE_DIR "" CACHE PATH "Optional self-contained C++/WinRT include directory")

-# The functional backend is currently Windows D3D12, so only Windows defaults
-# to carrying the loader. Linux keeps the capability-gated Vulkan scaffold
-# available to explicit developer builds without making a nonfunctional SDK
-# fetch part of every normal build.
+# Windows and Android carry the loader by default. Desktop Linux has the
+# same-device Vulkan backend too, but it needs a Dawn built with Aurora's patches
+# (Launcher/build-dawn-linux.sh), so it stays opt-in: Launcher/local-build.sh
+# --openxr, as the Steam Frame's native SteamOS build uses it.
 set(MKW_ENABLE_OPENXR_DEFAULT OFF)
 if(MKW_PLATFORM_WINDOWS OR MKW_PLATFORM_ANDROID)
    set(MKW_ENABLE_OPENXR_DEFAULT ON)
@@ -301,7 +302,9 @@ if(MKW_PROJECT_COMPILE_DEFINITIONS)
    add_compile_definitions(${MKW_PROJECT_COMPILE_DEFINITIONS})
 endif()

-if(MKW_PLATFORM_WINDOWS AND MKW_ENABLE_OPENXR)
+# The same-device Vulkan backend (openxr_vulkan_win32.cpp, on Windows and desktop
+# Linux) includes vulkan.h; the pin keeps it independent of the build machine.
+if((MKW_PLATFORM_WINDOWS OR MKW_PLATFORM_LINUX) AND MKW_ENABLE_OPENXR)
    include(FetchContent)
    FetchContent_Declare(vulkan_headers
        URL "https://github.com/KhronosGroup/Vulkan-Headers/archive/015e25c3c91b70eb1a754d36fb14c4ba6ad9b0b9.tar.gz"
@@ -452,7 +452,14 @@ elseif(MKW_PLATFORM_ANDROID)
    set(MKW_ANDROID_CPU "cortex-a77" CACHE STRING "AArch64 -mcpu target for the Android products")
    set(MKW_BASELINE_ARCH_FLAG -mcpu=${MKW_ANDROID_CPU})
 elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(aarch64|arm64|ARM64)$")
-    set(MKW_BASELINE_ARCH_FLAG -mcpu=native)
+    # A cross-build names its CPU; the Steam Frame's Snapdragon 8 Gen 3 exposes SVE (cortex-x4).
+    if(MKW_HEADSET STREQUAL "steam_frame")
+        set(_mkw_linux_cpu_default "cortex-x4")
+    else()
+        set(_mkw_linux_cpu_default "native")
+    endif()
+    set(MKW_LINUX_CPU "${_mkw_linux_cpu_default}" CACHE STRING "AArch64 -mcpu target for the Linux products")
+    set(MKW_BASELINE_ARCH_FLAG -mcpu=${MKW_LINUX_CPU})
 else()
    set(MKW_BASELINE_ARCH_FLAG "")
 endif()
@@ -2,7 +2,9 @@

 #pragma once

-#if defined(MKW_ENABLE_OPENXR) && defined(_WIN32)
+// Despite the name, also the desktop Linux backend (SteamOS on the Steam Frame): nothing in it is
+// Windows-specific. The Quest has its own two-device backend (openxr_vulkan.h).
+#if defined(MKW_ENABLE_OPENXR) && (defined(_WIN32) || (defined(__linux__) && !defined(__ANDROID__)))

 #include "vr/openxr_backend.h"
 #include "vr/openxr_runtime.h"
@@ -112,4 +114,4 @@ private:

 } // namespace mkw::vr

-#endif // defined(MKW_ENABLE_OPENXR) && defined(_WIN32)
+#endif // defined(MKW_ENABLE_OPENXR) && (defined(_WIN32) || (defined(__linux__) && !defined(__ANDROID__)))
@@ -35,6 +35,8 @@

 #if defined(__ANDROID__)
 #include <sys/system_properties.h>
+#endif
+#if defined(__linux__)
 #include <time.h>
 #endif

@@ -275,6 +277,9 @@ bool Injected(const char*) { return false; }

 #if defined(_WIN32)
 using ConvertNowToXrTime = XrResult(XRAPI_PTR*)(XrInstance, const LARGE_INTEGER*, XrTime*);
+#elif defined(__linux__)
+// Desktop Linux (SteamOS on the Steam Frame); Android declares it with its injection above.
+using ConvertNowToXrTime = XrResult(XRAPI_PTR*)(XrInstance, const struct timespec*, XrTime*);
 #endif
 #endif

@@ -666,7 +671,7 @@ void OpenXRInput::LoadInputClock() {
    if (enabled("XR_KHR_win32_convert_performance_counter_time")) {
        m_runtime->GetInstanceProcAddress("xrConvertWin32PerformanceCounterToTimeKHR", &function);
    }
-#elif defined(__ANDROID__)
+#elif defined(__linux__)
    if (enabled("XR_KHR_convert_timespec_time")) {
        m_runtime->GetInstanceProcAddress("xrConvertTimespecTimeToTimeKHR", &function);
    }
@@ -692,7 +697,7 @@ XrTime OpenXRInput::InputSampleTime(XrTime predicted_display_time) const {
                                                                                  &counter, &now))) {
        return predicted_display_time;
    }
-#elif defined(__ANDROID__)
+#elif defined(__linux__)
    timespec spec{};
    if (clock_gettime(CLOCK_MONOTONIC, &spec) != 0 ||
        XR_FAILED(reinterpret_cast<ConvertNowToXrTime>(m_convert_now_to_xr_time)(m_runtime->Instance(),
@@ -48,6 +48,14 @@
 #define XR_USE_TIMESPEC
 #include <openxr/openxr_platform.h>
 #define MKW_OPENXR_GRAPHICS_BACKEND 1
+#elif defined(__linux__)
+// Desktop Linux, SteamOS on the Steam Frame above all: the PC's same-device Vulkan backend, with
+// Dawn's own device bound to the session.
+#include "vr/openxr_vulkan_win32.h"
+#include <time.h>
+#define XR_USE_TIMESPEC
+#include <openxr/openxr_platform.h>
+#define MKW_OPENXR_GRAPHICS_BACKEND 1
 #else
 #define MKW_OPENXR_GRAPHICS_BACKEND 0
 #endif
@@ -85,9 +93,12 @@ void ConfigurePolicy(bool enabled) noexcept {
 #if defined(_WIN32)
 using GraphicsBackend = OpenXRWindowsBackend;

-#else
+#elif defined(__ANDROID__)
 using GraphicsBackend = OpenXRVulkanBackend;
 inline constexpr const char* kGraphicsBackendName = "Vulkan";
+#else
+using GraphicsBackend = OpenXRWindowsVulkanBackend;
+inline constexpr const char* kGraphicsBackendName = "Vulkan";
 #endif

 // Whether the immersive window's eyes can be aimed through the window, so that only the window is
@@ -412,6 +423,16 @@ public:
                                      "XR_FB_display_refresh_rate", "XR_EXT_performance_settings",
                                      "XR_VALVE_frame_controller_interaction"};
        AddHandMeshExtensions(config);
+#elif defined(__linux__) && !defined(__ANDROID__)
+        // As the PC's Vulkan binding, plus the clock conversion Linux uses and the Steam Frame's
+        // eye gaze for eye-tracked foveation.
+        config.required_extensions = {"XR_KHR_vulkan_enable2"};
+        config.optional_extensions = {"XR_KHR_convert_timespec_time", "XR_FB_display_refresh_rate",
+                                      "XR_EXT_performance_settings", "XR_VALVE_frame_controller_interaction"};
+        if (RuntimeConfigFile::VrEyeTrackedFoveation()) {
+            config.optional_extensions.push_back("XR_EXT_eye_gaze_interaction");
+        }
+        AddHandMeshExtensions(config);
 #else
        // Either Vulkan binding extension is acceptable; the backend picks
        // whichever the runtime enabled, preferring enable2.
@@ -718,9 +739,10 @@ private:
    void ApplyGraphicsRequirements(AuroraConfig& aurora_config) {
        aurora_config.desiredBackend = kRequiredAuroraBackend;
        aurora_config.xrInterop = true;
-#if defined(__ANDROID__)
-        // Foveated rendering: fragment density maps are decided with the device. They put a flag on
-        // every render pipeline, so a session launched with foveation off does without them.
+#if !defined(_WIN32)
+        // Foveated rendering (the Quest's and desktop Linux's patched Dawn): fragment density maps
+        // are decided with the device. They put a flag on every render pipeline, so a session
+        // launched with foveation off does without them.
        aurora_config.xrFragmentDensityMap = RuntimeConfigFile::VrFoveation() != "off";
 #endif
 #if defined(_WIN32)
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-3.0-or-later

-#if defined(MKW_ENABLE_OPENXR) && defined(_WIN32)
+#if defined(MKW_ENABLE_OPENXR) && (defined(_WIN32) || (defined(__linux__) && !defined(__ANDROID__)))

 // OpenXR's Vulkan structures are selected when openxr_platform.h is parsed.
 #define XR_USE_GRAPHICS_API_VULKAN
@@ -180,7 +180,11 @@ public:
        if (XR_FAILED(get(runtime.Instance(), runtime.SystemId(), &requirements))) return Fail("Vulkan requirements query failed");
        requirements_ = {requirements.minApiVersionSupported, requirements.maxApiVersionSupported};
        AuroraDawnVulkanHooks hooks{this, CreateInstance, CreateDevice, GetPhysical};
+#if defined(_WIN32)
        if (!aurora_vulkan_win32_configure(&hooks)) return Fail("PC Vulkan OpenXR requires the custom Dawn library with Aurora Vulkan ABI 1; rebuild/install it with Launcher/Build-DawnVulkan.ps1");
+#else
+        if (!aurora_vulkan_win32_configure(&hooks)) return Fail("Linux Vulkan OpenXR requires a Dawn built with Aurora's patches (Aurora Vulkan ABI 1); build it with Launcher/build-dawn-linux.sh");
+#endif
        hooks_installed_ = true;
        {
            std::lock_guard lock(submission_mutex_);
@@ -1315,4 +1319,4 @@ const std::string& OpenXRWindowsVulkanBackend::LastError() const { return m_impl

 } // namespace mkw::vr

-#endif // defined(MKW_ENABLE_OPENXR) && defined(_WIN32)
+#endif // defined(MKW_ENABLE_OPENXR) && (defined(_WIN32) || (defined(__linux__) && !defined(__ANDROID__)))