Bug 303811 – Blank WebView on NVIDIA RTX 50 series (Blackwell) - GBM buffer fail

• Status: NEW
• Component: WebKitGTK

Created attachment 477669 [details]
Settings panel NOT bugged QtWebengine/Blink NVIDIA dGPU

𝗢𝘃𝗲𝗿𝘃𝗶𝗲𝘄:
WebKitGTK WebView renders blank on NVIDIA RTX 5070 Laptop GPU (Blackwell 
architecture). GBM buffer creation fails with "Invalid argument" error. 
The GTK window appears but no web content is visible.

𝗦𝘁𝗲𝗽𝘀 𝘁𝗼 𝗥𝗲𝗽𝗿𝗼𝗱𝘂𝗰𝗲:
1. Use a system with NVIDIA RTX 50 series GPU (Blackwell) and proprietary 
   driver 580.x
2. Ensure nvidia-drm.modeset=1 is enabled
3. Launch any WebKitGTK application (tested: Wails app, Epiphany, Foliate)
4. Observe WebView content area

𝗔𝗰𝘁𝘂𝗮𝗹 𝗥𝗲𝘀𝘂𝗹𝘁𝘀:
WebView is completely blank (black). Right-click context menu appears, 
confirming the WebView exists, but no content renders. Console outputs:

    Failed to create GBM buffer of size 1030x1024: Invalid argument

𝗘𝘅𝗽𝗲𝗰𝘁𝗲𝗱 𝗥𝗲𝘀𝘂𝗹𝘁𝘀:
WebView should render web content normally.

𝗕𝘂𝗶𝗹𝗱 𝗗𝗮𝘁𝗲 & 𝗛𝗮𝗿𝗱𝘄𝗮𝗿𝗲:
    WebKitGTK: 2.50.3-1
    OS: Arch Linux, kernel 6.12.60-1-lts
    GPU: NVIDIA GeForce RTX 5070 Laptop GPU (Blackwell)
    Driver: nvidia-utils 580.105.08-5, nvidia-open-dkms
    Mesa: 25.3.1-2
    GStreamer: 1.26.9-1
    Display: X11 (Xfwm4)
    nvidia-drm.modeset: Y

𝗔𝗱𝗱𝗶𝘁𝗶𝗼𝗻𝗮𝗹 𝗕𝘂𝗶𝗹𝗱𝘀 𝗮𝗻𝗱 𝗣𝗹𝗮𝘁𝗳𝗼𝗿𝗺𝘀:
    Does NOT occur: Same system using integrated Intel iGPU (works perfectly)
    Does NOT occur: Same system using Mesa software EGL — works but unusable 
                    performance

𝗔𝗱𝗱𝗶𝘁𝗶𝗼𝗻𝗮𝗹 𝗜𝗻𝗳𝗼𝗿𝗺𝗮𝘁𝗶𝗼𝗻:

Workaround WEBKIT_DISABLE_DMABUF_RENDERER=1 allows rendering, but CSS 
backdrop-filter: blur() no longer functions.

Workarounds tested that do NOT resolve the issue:
    WEBKIT_DMABUF_USE_MODIFIERS=0
    MESA_GBM_NO_MODIFIERS=1  
    GBM_BACKEND=nvidia-drm
    __NV_PRIME_RENDER_OFFLOAD=0
    __GL_DISABLE_EXPLICIT_SYNC=1
    GSK_RENDERER=ngl/gl/vulkan
    GDK_BACKEND=x11

Note: This is not a duplicate of Bug #261874, which was closed as RESOLVED 
MOVED with the statement that the issue was fixed in current versions. RTX 50 
series (Blackwell) is a new architecture (released May 2025), and the error 
differs ("Invalid argument" vs previous "Permission denied" or NVKMS errors).

QtWebEngine/Blink renders correctly on this same hardware, suggesting the 
issue is specific to WebKitGTK's GBM buffer allocation.

𝗦𝗲𝗰𝗼𝗻𝗱𝗮𝗿𝘆 𝗶𝘀𝘀𝘂𝗲 — 𝗯𝗮𝗰𝗸𝗱𝗿𝗼𝗽-𝗳𝗶𝗹𝘁𝗲𝗿 𝗯𝗿𝗼𝗸𝗲𝗻 𝘄𝗵𝗲𝗻 𝗗𝗠𝗔𝗕𝗨𝗙 𝗱𝗶𝘀𝗮𝗯𝗹𝗲𝗱:

When using WEBKIT_DISABLE_DMABUF_RENDERER=1 as a workaround, CSS 
backdrop-filter: blur() does not render. The element appears but the blur 
effect is absent — background content shows through unblurred.

This also occurs with GSK_RENDERER=vulkan (which allows rendering without 
disabling DMABUF entirely).

This means there is currently NO working configuration for NVIDIA Blackwell 
users who require backdrop-filter effects:
    - DMABUF enabled → blank WebView
    - DMABUF disabled → backdrop-filter broken
    - Vulkan renderer → backdrop-filter broken

I am including this here rather than filing a separate bug report as the 
issues are related — the backdrop-filter breakage is a direct consequence 
of the only available workaround for the primary GBM buffer issue.

My application supports both WebKitGTK and QtWebEngine runtimes with the 
same frontend code. I can confirm that neither issue exists in QtWebEngine 
on this same NVIDIA Blackwell hardware — both rendering and backdrop-filter 
work correctly (see attachments).

If helpful for reproducing, my application is available at:
https://github.com/tassa-yoniso-manasi-karoto/langkit/releases
Linux release zips include both WebKit 4.0 and 4.1 builds.


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𝗔𝘁𝘁𝗮𝗰𝗵𝗺𝗲𝗻𝘁 𝗗𝗲𝘀𝗰𝗿𝗶𝗽𝘁𝗶𝗼𝗻𝘀 
=====================

𝗻𝗼_𝘄𝗲𝗯𝘃𝗶𝗲𝘄.𝘄𝗲𝗯𝗽
Blank WebView on NVIDIA RTX 5070 (Blackwell). GTK window renders but WebView 
content is black. Context menu confirms WebView exists. Console shows 
"Failed to create GBM buffer of size 1030x1024: Invalid argument".

𝗦𝗲𝘁𝘁𝗶𝗻𝗴𝘀_𝗽𝗮𝗻𝗲𝗹_𝗡𝗢𝗧_𝗯𝘂𝗴𝗴𝗲𝗱_𝗤𝘁𝗪𝗲𝗯𝗲𝗻𝗴𝗶𝗻𝗲-𝗕𝗹𝗶𝗻𝗸.𝘄𝗲𝗯𝗽
Expected behavior: backdrop-filter blur working correctly in QtWebEngine 
(Blink) on the same NVIDIA RTX 5070 system. Background is properly blurred 
behind the Settings modal.

𝗦𝗲𝘁𝘁𝗶𝗻𝗴𝘀_𝗽𝗮𝗻𝗲𝗹_𝗯𝘂𝗴𝗴𝗲𝗱_𝘄𝗶𝘁𝗵𝗼𝘂𝘁_𝗕𝗚_𝗯𝗹𝘂𝗿.𝘄𝗲𝗯𝗽
Broken backdrop-filter in WebKitGTK with WEBKIT_DISABLE_DMABUF_RENDERER=1 
workaround. The Settings modal renders but blur does not apply — background 
content overlaps, making UI unusable.

Created attachment 477670 [details]
Settings panel bugged without BG blur NVIDIA dGPU

Created attachment 477671 [details]
no webview

[Michael Catanzaro]

Pretty sure blur (and other 3D transforms) is not expected to work with dmabuf renderer disabled.