Cage fails to start with two virtio cards, (Even though I am using `-m last`)

[n3rdopolis]

This might be a wlroots issue, but I am reporting to Cage first. Since Cage has the option to only use one output, and I am using it.
This is on a VM with two virtual cards, so a /dev/dri/card0 and /dev/dri/card1. They are both gl-less virtio, but it also happens with two qxls

I am building Cage's wlroots with meson setup -Ddebug=false -Doptimization=s --prefix=$INSTALLDIR --libdir=$INSTALLDIR/lib/$(dpkg-architecture -qDEB_HOST_MULTIARCH) -Dwerror=false build -Dxcb-errors=disabled -Dxwayland=disabled -Drenderers= -Dbackends=drm,libinput -Dallocators= -Dcolor-management=disabled -Dlibliftoff=disabled

I am building Cage with meson setup -Dbuildtype=plain -Ddebug=false -Doptimization=s --prefix=$INSTALLDIR --libdir=$INSTALLDIR/lib/$(dpkg-architecture -qDEB_HOST_MULTIARCH) -Dwerror=false build

Below is my output running Cage with cage -m last -d -s -- foot

00:00:00.000 [INFO] [backend/backend.c:342] Loading user-specified backends due to WLR_BACKENDS: libinput,drm
00:00:00.000 [INFO] [libseat] [libseat/backend/seatd.c:64] Could not connect to socket /run/seatd.sock: No such file or directory
00:00:00.000 [INFO] [libseat] [libseat/libseat.c:76] Backend 'seatd' failed to open seat, skipping
00:00:00.001 [INFO] [libseat] [libseat/libseat.c:73] Seat opened with backend 'logind'
00:00:00.001 [INFO] [backend/session/session.c:108] Successfully loaded libseat session
00:00:00.003 [INFO] [backend/backend.c:248] Found 2 GPUs
00:00:00.003 [INFO] [backend/drm/backend.c:225] Initializing DRM backend for /dev/dri/card1 (virtio_gpu)
00:00:00.003 [INFO] [backend/drm/drm.c:115] DRM_CLIENT_CAP_CURSOR_PLANE_HOTSPOT supported
00:00:00.003 [INFO] [backend/drm/drm.c:310] Found 1 DRM CRTCs
00:00:00.003 [INFO] [backend/drm/drm.c:268] Found 2 DRM planes
00:00:00.003 [INFO] [backend/drm/backend.c:225] Initializing DRM backend for /dev/dri/card0 (virtio_gpu)
00:00:00.003 [INFO] [backend/drm/drm.c:115] DRM_CLIENT_CAP_CURSOR_PLANE_HOTSPOT supported
00:00:00.003 [INFO] [backend/drm/drm.c:310] Found 1 DRM CRTCs
00:00:00.003 [INFO] [backend/drm/drm.c:268] Found 2 DRM planes
00:00:00.003 [INFO] [util/env.c:25] Loading WLR_RENDERER option: pixman
00:00:00.003 [INFO] [render/pixman/renderer.c:328] Creating pixman renderer
00:00:00.003 [ERROR] [backend/drm/renderer.c:23] Renderer did not support importing DMA-BUFs
00:00:00.003 [INFO] [backend/drm/backend.c:181] Failed to initialize mgpu blit renderer, falling back to scanning out from primary GPU
00:00:00.003 [INFO] [util/env.c:25] Loading WLR_RENDERER option: pixman
00:00:00.003 [INFO] [render/pixman/renderer.c:328] Creating pixman renderer
00:00:00.015 [INFO] [../seat.c:141] Input device QEMU Virtio Tablet cannot be mapped to an output device

00:00:00.018 [INFO] [../seat.c:141] Input device ImExPS/2 Generic Explorer Mouse cannot be mapped to an output device

00:00:00.018 [INFO] [util/env.c:9] Loading WLR_LIBINPUT_NO_DEVICES option: 1
00:00:00.018 [INFO] [backend/drm/drm.c:1741] Scanning DRM connectors on /dev/dri/card1
00:00:00.018 [INFO] [backend/drm/drm.c:1796] Found connector 'Virtual-1'
00:00:00.018 [INFO] [backend/drm/drm.c:1821] 'Virtual-1' connected
00:00:00.018 [INFO] [backend/drm/drm.c:1610] Detected modes:
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1280x800 @ 74.994 Hz (preferred)
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   5120x2160 @ 50.000 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   4096x2160 @ 50.000 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   3840x2160 @ 60.000 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   3840x2160 @ 59.940 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   3840x2160 @ 50.000 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1920x1440 @ 60.000 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   2560x1080 @ 50.000 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1856x1392 @ 59.995 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1792x1344 @ 60.000 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   2048x1152 @ 60.000 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1920x1200 @ 59.885 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1920x1080 @ 60.000 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1920x1080 @ 50.000 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1600x1200 @ 60.000 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1680x1050 @ 59.954 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1400x1050 @ 59.978 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1280x1024 @ 60.020 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1440x900 @ 59.887 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1280x960 @ 60.000 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1360x768 @ 60.015 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1280x768 @ 59.870 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   1024x768 @ 60.004 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   800x600 @ 60.317 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   640x480 @ 60.000 Hz 
00:00:00.018 [INFO] [backend/drm/drm.c:1634]   640x480 @ 59.940 Hz 
00:00:00.018 [INFO] [util/env.c:9] Loading WLR_NO_HARDWARE_CURSORS option: 1
00:00:00.018 [INFO] [backend/drm/drm.c:1671] Physical size: 320x200
00:00:00.018 [INFO] [backend/drm/drm.c:1855] connector Virtual-1: Requesting modeset
00:00:00.023 [INFO] [backend/drm/drm.c:944] connector Virtual-1: Modesetting with 1280x800 @ 74.994 Hz
00:00:00.023 [INFO] [backend/drm/drm.c:1741] Scanning DRM connectors on /dev/dri/card0
00:00:00.023 [INFO] [backend/drm/drm.c:1796] Found connector 'Virtual-2'
00:00:00.023 [INFO] [backend/drm/drm.c:1821] 'Virtual-2' connected
00:00:00.023 [INFO] [backend/drm/drm.c:1610] Detected modes:
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1280x800 @ 74.994 Hz (preferred)
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   5120x2160 @ 50.000 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   4096x2160 @ 50.000 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   3840x2160 @ 60.000 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   3840x2160 @ 59.940 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   3840x2160 @ 50.000 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1920x1440 @ 60.000 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   2560x1080 @ 50.000 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1856x1392 @ 59.995 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1792x1344 @ 60.000 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   2048x1152 @ 60.000 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1920x1200 @ 59.885 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1920x1080 @ 60.000 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1920x1080 @ 50.000 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1600x1200 @ 60.000 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1680x1050 @ 59.954 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1400x1050 @ 59.978 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1280x1024 @ 60.020 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1440x900 @ 59.887 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1280x960 @ 60.000 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1360x768 @ 60.015 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1280x768 @ 59.870 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   1024x768 @ 60.004 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   800x600 @ 60.317 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   640x480 @ 60.000 Hz 
00:00:00.023 [INFO] [backend/drm/drm.c:1634]   640x480 @ 59.940 Hz 
00:00:00.023 [INFO] [util/env.c:9] Loading WLR_NO_HARDWARE_CURSORS option: 1
00:00:00.023 [INFO] [backend/drm/drm.c:1671] Physical size: 320x200
00:00:00.023 [INFO] [backend/drm/drm.c:1855] connector Virtual-2: Requesting modeset
00:00:00.028 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.072 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.106 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.139 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.171 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.202 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.213 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.223 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.232 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.240 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.249 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.257 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.265 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.272 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.279 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.286 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.291 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.296 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.300 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.304 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.308 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.312 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.314 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.316 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.318 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.319 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.319 [INFO] [backend/drm/drm.c:948] connector Virtual-1: Turning off
00:00:00.320 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
00:00:00.329 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test
 err: wayland.c:1751: no monitors available
00:00:00.475 [ERROR] [types/output/swapchain.c:109] Swapchain for output 'Virtual-2' failed test

Sometimes I get a crash, sometimes I don't. It's odd.

[emersion]

This kind of multi-GPU setup (with the Pixman renderer and DRM dumb buffer allocator) is not supported by wlroots at this time.

[n3rdopolis]

Makes sense. I'm using -m last though, for now I am using a workaround using udevadm to get the first GPU in the seat to export WLR_DRM_DEVICES...
Is it possible to make Cage only use one GPU (for -m last)?

[emersion]

-m doesn't have an influence on the GPUs which get loaded. You can set WLR_DRM_DEVICES to make wlroots only load a single card.

[n3rdopolis]

Yeah, I will use that as a workaround. Using udevadm so it's seat-aware too.