marfrit
c14c22f942
Adds 0007-panvk-bifrost-xfb-component-base-fix.patch — eliminates a
reliable SIGSEGV in vkCreateGraphicsPipeline whenever an XFB-bound
vertex output is declared with non-zero `layout (component=N)`.
Surfaced by dEQP-VK.transform_feedback.simple.holes_vert (Mali-G52 r1
MC1, PAN_ARCH 7). Backtrace lands 11 frames into libvulkan_panfrost.so
called from vkt::TransformFeedback::TransformFeedbackHolesInstance::
iterate.
Root cause: iter17's lower_xfb_output_iter17 (and upstream
pan_nir_lower_xfb, which has the identical `// TODO`) computes the
source-channel mask as `mask << channel_idx`, where channel_idx is
the varying-location component (0..3) but src only contains channels
starting at nir_intrinsic_component(intr). For a scalar declared
component=2, the lowering computed `mask << 2` against a 1-component
src — out-of-range; the malformed nir_def segfaulted in downstream
NIR constant-folding (nir_constant_expressions.c::evaluate_*).
Fix translates channel_idx to source-channel space by subtracting
nir_intrinsic_component(intr) before shifting the mask, and replaces
the elided release-mode asserts with explicit release-mode guards
(closes the same elision class as the original bug).
Verified on PineTab2 (Mali-G52 r1 MC1, PAN_ARCH 7) against vulkan-cts
1.3.10.0:
- holes_vert / holes_extra_draw_vert no longer SIGSEGV (now Fail
on color-check; that is a separate iter20 finding).
- basic_*: 36/36 Pass. depth_clip_*: 1 Pass + 4 NotSupported.
lines_or_triangles*: 16 NotSupported. 0 Fail across the set.
Caveat (not regressions): max_output_components_64/_128/_256 were
never reached on the r5 sweep — watchdog killed transform_feedback
after the holes_vert crash. With this fix in place, they now run
and surface their own pre-existing coredumps, confirmed on shipped
r6 baseline too. iter20+ territory.
Phase 5 (2nd-model) review: APPROVE WITH CHANGES (non-blocking).
Changes applied: release-mode defensive guards on both preconditions
plus a dispatcher-side comment clarifying the i*2+j semantics.
Cross-refs:
- ~/src/panvk-bifrost/iter19/phase{0,1,2,3}_holes_vert*.md
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
mesa-panvk-bifrost
Patched Mesa libvulkan_panfrost.so exposing Bifrost-gen Mali GPUs
(Mali-G31/G52/G72/G76, PAN_ARCH 6/7) to Chromium-family browsers'
Vulkan compositor.
Result of the panvk-bifrost campaign (~/src/panvk-bifrost/),
iter9 close 2026-05-20 (technical milestone — operator-confirmed Brave
window) followed by this package as the actual delivery.
What it solves
Stock Chromium / Brave on Bifrost SBCs (PineTab2, etc.) currently dies at GL bindings init:
ERROR: ui/gl/gl_context_egl.cc:120 GLES3 is unsupported and ES version fallback is disabled
ERROR: ui/gl/init/gl_factory.cc:111 Requested GL implementation not found
ERROR: components/viz/service/main/viz_main_impl.cc:189 Exiting GPU process due to errors during initialization
This package makes Brave's Vulkan compositor path work on Bifrost, side-stepping the failing GL stack. Browser chrome and standard page rendering work.
Known limitations (not addressed)
- WebGL / WebGL2 in-page: blocked. ANGLE needs
VK_EXT_transform_feedbackto expose GLES3 contexts; PanVk-Bifrost doesn't currently support that. Sites using WebGL will degrade or refuse. - VAAPI hardware video decode: unrelated to this package — see the
libva-v4l2-request-fourierpackage for that path.
Install
# Ensure [marfrit] is in /etc/pacman.conf, then:
sudo pacman -Sy mesa-panvk-bifrost
Use
brave-vulkan # launches Brave with Vulkan
brave-vulkan https://www.example.com
brave-vulkan --your-flags-here # extra args passed through
The launcher sets:
VK_ICD_FILENAMES=/usr/lib/panvk-bifrost/icd.json(the patched driver)PAN_I_WANT_A_BROKEN_VULKAN_DRIVER=1(Mesa upstream gate)MESA_VK_VERSION_OVERRIDE=1.2(apiVersion bump for ANGLE)- Brave flags:
--use-gl=disabled --enable-features=Vulkan --use-vulkan=native --ozone-platform=x11 --no-sandbox --disable-gpu-sandbox --ignore-gpu-blocklist
What's in the package
/usr/lib/panvk-bifrost/libvulkan_panfrost.so— patched Mesa Vulkan driver (Mesa 26.0.6 + 2 sed-applied patches)/usr/lib/panvk-bifrost/icd.json— Vulkan ICD JSON pointing at the patched .so (NOT auto-loaded; only viaVK_ICD_FILENAMES)/usr/bin/brave-vulkan— launcher script
System Mesa is untouched. The stock /usr/lib/libvulkan_panfrost.so and
/usr/share/vulkan/icd.d/panfrost_icd.json continue to work for any
other Vulkan app.
Co-existence
Both stock Mesa and this package can be installed. Stock Vulkan apps
(vulkaninfo, vkcube, etc.) use the stock driver by default. Only
apps started via brave-vulkan (or with VK_ICD_FILENAMES manually
set to our path) use the patched driver.
Campaign close criterion
Per feedback_package_done_means_installable
three-point check:
- PR merged to
marfrit-packages - CI green AND
packages.reauktion.de/arch/aarch64/mesa-panvk-bifrost-*.pkg.tar.zstexists pacman -Ss mesa-panvk-bifroston a fresh consumer host (e.g. ohm afterpacman -Syufrom clean state) returns the package + brave-vulkan launches
When all three pass, panvk-bifrost iter9 closes.