radv: add RADV_DEBUG=nomeshshader

This option will be used to disable VK_EXT_mesh_shader in Mesa CI
for GFX11 because running task shader tests in parallel can hang the
GPU.

Gitlab: https://gitlab.freedesktop.org/mesa/mesa/-/issues/10051
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25969>

docs/envvars.rst

@@ -1259,6 +1259,8 @@ RADV driver environment variables
       disable directly recording command buffers in GPU-visible memory
    ``nomemorycache``
       disable memory shaders cache
+   ``nomeshshader``
+      disable mesh shader support on GFX10.3+
    ``nongg``
       disable NGG for GFX10 and GFX10.3
    ``nonggc``

src/amd/vulkan/radv_debug.h

@@ -71,6 +71,7 @@ enum {
    RADV_DEBUG_NO_GPL = 1ull << 40,
    RADV_DEBUG_VIDEO_ARRAY_PATH = 1ull << 41,
    RADV_DEBUG_NO_RT = 1ull << 42,
+   RADV_DEBUG_NO_MESH_SHADER = 1ull << 43,
 };
 
 enum {

src/amd/vulkan/radv_instance.c

@@ -76,6 +76,7 @@ static const struct debug_control radv_debug_options[] = {{"nofastclears", RADV_
                                                           {"nogpl", RADV_DEBUG_NO_GPL},
                                                           {"videoarraypath", RADV_DEBUG_VIDEO_ARRAY_PATH},
                                                           {"nort", RADV_DEBUG_NO_RT},
+                                                          {"nomeshshader", RADV_DEBUG_NO_MESH_SHADER},
                                                           {NULL, 0}};
 
 const char *

src/amd/vulkan/radv_physical_device.c

@@ -64,6 +64,9 @@ radv_perf_query_supported(const struct radv_physical_device *pdev)
 static bool
 radv_taskmesh_enabled(const struct radv_physical_device *pdevice)
 {
+   if (pdevice->instance->debug_flags & RADV_DEBUG_NO_MESH_SHADER)
+      return false;
+
    return pdevice->use_ngg && !pdevice->use_llvm && pdevice->rad_info.gfx_level >= GFX10_3 &&
           !(pdevice->instance->debug_flags & RADV_DEBUG_NO_COMPUTE_QUEUE) && pdevice->rad_info.has_gang_submit;
 }