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VkLayer_MESA_device_select can cause containers.py test failure

On my X280 running Debian testing/unstable, tests/pressure-vessel/containers.py is currently failing as a result of upgrading Mesa to a version where VkLayer_MESA_device_select and lavapipe are included.

To reproduce

  • Debian unstable, up to date as of 2021-01-05
  • mesa-vulkan-drivers:amd64 and :i386 installed
  • Intel iGPU (UHD Graphics 620, KBL GT2)
  • lavapipe driver also enabled
  • steam-runtime-tools commit cf41c83a
  • Configured with -Dtest_containers_dir=/path/to/SteamLinuxRuntime/depot
  • A pressure-vessel relocatable build, done under scout, is installed in /path/to/SteamLinuxRuntime/depot/pressure-vessel
  • Command used to reproduce: AUTOPKGTEST_ARTIFACTS=$(pwd)/_build/host/artifacts PRESSURE_VESSEL_VERBOSE=1 G_MESSAGES_DEBUG=all meson test -C _build/host
  • _build/host/artifacts/host-srsi.json says:
    • Intel(R) UHD Graphics 620 (KBL GT2) was enumerated first by *-linux-gnu-vulkaninfo for x11/vulkan, in both word sizes
    • Order of vulkan -> icds:
      1. /usr/share/vulkan/icd.d/intel_icd.x86_64.json (iGPU)
      2. /usr/share/vulkan/icd.d/lvp_icd.x86_64.json (lavapipe)
      3. /usr/share/vulkan/icd.d/radeon_icd.x86_64.json (not used)
      4. /usr/share/vulkan/icd.d/intel_icd.i686.json (iGPU)
      5. /usr/share/vulkan/icd.d/lvp_icd.i686.json (lavapipe)
      6. /usr/share/vulkan/icd.d/radeon_icd.i686.json (not used)
  • In the pressure-vessel debug log, the drivers are consistently enumerated in that same order, which I assume is readdir() order. #0 is the 64-bit iGPU, #1 is the 64-bit lavapipe, ..., #5 is the 32-bit Radeon.
  • In the pressure-vessel debug log, VK_ICD_FILENAMES is consistently set with 0-x86_64-linux-gnu.json first, ..., 5-i386-linux-gnu.json last.

Expected result

GPUs are enumerated in the container in the same order as on the host system (whatever that is). In my case, that means *-linux-gnu-vulkaninfo inside the container should list the iGPU before the lavapipe software renderer.

Actual result

Despite VkLayer_MESA_device_select apparently being imported into the container successfully, *-linux-gnu-vulkaninfo inside the container (both soldier and scout) enumerates the lavapipe software GPU first. This is a mismatch between the behaviour outside and inside the container, causing the test to fail.

Workaround

Test with NODEVICE_SELECT=1 in the environment.

Out of scope

Vulkan device enumeration is done in readdir() order, although VkLayer_Mesa_device_select subsequently reshuffles it. We do not attempt to change any of that: whatever arbitrary order we get from the OS, we present the same arbitrary order to the application.

Edited by Simon McVittie