OK, thanks. In that case the correct status of the bug is "Fix
Released". If we knew *what* change fixed it then we could try to get
the same fix into 18.04. Probably Mesa, I guess?
** Changed in: libsdl2 (Ubuntu)
Status: Incomplete => Fix Released
** Changed in: mesa (Ubuntu)
Status: Incomplete => Fix Released
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https://bugs.launchpad.net/bugs/1902853
Title:
Failure to create core GL context with llvmpipe when using
GLX_ARB_context_flush_control
Status in libsdl2 package in Ubuntu:
Fix Released
Status in mesa package in Ubuntu:
Fix Released
Bug description:
When using llvmpipe on the non-HWE xorg version GL core context
creation fails when using "GLX_ARB_context_flush_control" even though
the driver reports that the extension is supported.
Apologies if xorg is the wrong package here, this could be a libgl1
-mesa-dri/glx bug instead, it's unclear to me where the fault lies in
the graphics stack.
xserver-common:
Installed: 2:1.19.6-1ubuntu4.7
Candidate: 2:1.19.6-1ubuntu4.7
linux-generic:
Installed: 4.15.0.122.109
Candidate: 4.15.0.122.109
Steps to reproduce on Ubuntu Server:
1. Install Ubuntu 18.04 server edition in a VM, or other hardware without a
physical graphics device
2. Install the desktop with "sudo apt install ubuntu-desktop"
3. Reboot
4. Compile and run the attached file
Steps to reproduce on Ubuntu Desktop:
1. Install Ubuntu 18.04 desktop edition in a VM, or other hardware without a
physical graphics device
2. Remove the HWE packages with "apt remove *-hwe-18.04" and then "apt
install xserver-xorg-core ubuntu-desktop xserver-xorg xserver-xorg-video-all
xserver-xorg-input-all libgl1-mesa-dri libgl1-mesa-glx" to get things back to
normal
3. Reboot
4. Compile and run the attached file
Both examples produce:
"Could not create GL context: BadValue (integer parameter out of range for
operation)"
For both cases, upgrading to (or staying on) the HWE stack allows
creating the core 3.3 context successfully.
Debugging:
I've stepped all the way into libxcb for the context creation at
src/glx.c:3258, with a call to
"xcb_glx_create_context_attribs_arb_checked", but haven't managed to
link this up to a received request in another process. The request is
rejected with BadValue.
BadVaue in this instance could mean one of two things according to GL spec:
1. The GLX_RENDER_TYPE attribute is invalid
2. An attribute or it's bitmask are not recognized.
We can likely rule out 1 as GLX_RENDER_TYPE is correctly set to
opengl. Option 2 allows looking at it at a higher level. SDL2 adds
`GLX_CONTEXT_RELEASE_BEHAVIOUR_ARB=GLX_CONTEXT_RELEASE_BEHAVIOUR_FLUSH_ARB`
to the attributes (at src/video/x11/SDL_x11opengl.c:720) by default
when it detects the `GLX_ARB_context_flush_control` extension is
present, which should be a no-op and the default setting. `glxinfo`
and other gl functions all show that `GLX_ARB_context_flush_control`
is present, but removing that usage from the attributes list (by
removing lines 720 to 726 avoids the issue and we are given a valid GL
context.
Due to this, I think something in the graphics stack is rejecting the
usage of GLX_ARB_context_flush_control, even though it's claiming to
support it through other gl calls. The llvmpipe GL driver reports core
support up to 3.3 as well, so this shouldn't be an issue. I also
suspect it's simply something that's been fixed more recently, as
installing the newer HWE versions of xorg (and the kernel) fixes the
issue.
I wouldn't expect to have to upgrade to the HWE stack to be able to get a
working GL context this way, so I'm reporting this to check if it's a known
issue or if there's a fix that can be made.
The attached file depends on "libsdl2-dev" and can be compiled and run with:
"g++ main.cpp -I/usr/include/SDL2 -lSDL2 -lGL && ./a.out"
ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: xorg 1:7.7+19ubuntu7.1
ProcVersionSignature: Ubuntu 5.4.0-52.57~18.04.1-generic 5.4.65
Uname: Linux 5.4.0-52-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.18
Architecture: amd64
CompositorRunning: None
CurrentDesktop: ubuntu:GNOME
Date: Wed Nov 4 09:16:16 2020
DistUpgraded: Fresh install
DistroCodename: bionic
DistroVariant: ubuntu
ExtraDebuggingInterest: Yes, including running git bisection searches
GraphicsCard:
VMware SVGA II Adapter [15ad:0405] (prog-if 00 [VGA controller])
Subsystem: VMware SVGA II Adapter [15ad:0405]
InstallationDate: Installed on 2020-11-03 (0 days ago)
InstallationMedia: Ubuntu-Server 18.04.5 LTS "Bionic Beaver" - Release amd64
(20200806.1)
Lsusb:
Bus 001 Device 002: ID 80ee:0021 VirtualBox USB Tablet
Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
MachineType: innotek GmbH VirtualBox
ProcEnviron:
TERM=xterm-256color
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=C.UTF-8
SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-5.4.0-52-generic
root=/dev/mapper/ubuntu--vg-ubuntu--lv ro maybe-ubiquity
Renderer: Software
SourcePackage: xorg
Symptom: display
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 12/01/2006
dmi.bios.vendor: innotek GmbH
dmi.bios.version: VirtualBox
dmi.board.name: VirtualBox
dmi.board.vendor: Oracle Corporation
dmi.board.version: 1.2
dmi.chassis.type: 1
dmi.chassis.vendor: Oracle Corporation
dmi.modalias:
dmi:bvninnotekGmbH:bvrVirtualBox:bd12/01/2006:svninnotekGmbH:pnVirtualBox:pvr1.2:rvnOracleCorporation:rnVirtualBox:rvr1.2:cvnOracleCorporation:ct1:cvr:
dmi.product.family: Virtual Machine
dmi.product.name: VirtualBox
dmi.product.version: 1.2
dmi.sys.vendor: innotek GmbH
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.101-2~18.04.1
version.libgl1-mesa-dri: libgl1-mesa-dri 20.0.8-0ubuntu1~18.04.1
version.libgl1-mesa-glx: libgl1-mesa-glx 20.0.8-0ubuntu1~18.04.1
version.xserver-xorg-core: xserver-xorg-core 2:1.19.6-1ubuntu4.7
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:18.0.1-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel
2:2.99.917+git20171229-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.15-2
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