id = 553
title = "Virtio-vga with blobs on fails, when qemu compiled with enabled modules"
state = "closed"
created_at = "2021-08-21T19:15:08.697Z"
closed_at = "2021-09-01T11:37:49.404Z"
labels = ["Build System", "Regression"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/553"
host-os = "Manjaro Linux"
host-arch = "x86 (others may be affected too)"
qemu-version = "QEMU emulator version 6.0.94 (v6.1.0-rc4-dirty)"
guest-os = "n/a"
guest-arch = "n/a"
description = """When using qemu configured with `--enabled-modules` and starting qemu with command line above, qemu crashes with following output:
```
qemu-system-x86_64: -device virtio-vga,blob=on: cannot enable blob resources without udmabuf
```
While qemu configured without `--enabled-modules` runs this command successfully."""
reproduce = """1. Get latest qemu source code
2. Build qemu `mkdir build && cd build && ../configure && ninja`
3. Check if following command runs without errors and show sdl qemu window
 ```
 sudo ./qemu-system-x86_64  \\
      -object memory-backend-memfd,id=mem1,size=512M \\
      -machine memory-backend=mem1 \\
      -display sdl \\
      -device virtio-vga,blob=on

 ```
4. Then try to build with modules enabled  `mkdir build && cd build && ../configure --enable-modules && ninja`
5. Try to do step 3 again"""
additional = """I tried to debug this bug, and found that problem is with function `virtio_gpu_have_udmabuf`: when qemu is build without modules this function is from `hw/display/virtio-gpu-udmabuf.c` (which is correct), but when qemu compiled with modules this function comes from `stubs/virtio-gpu-udmabuf.c` and when `hw-display-virtio-gpu.so` is loaded, `virtio_gpu_have_udmabuf` is not replaced, and remains function from stub (which always return 0) and command fails.

I think I will submit patch that fix it tomorrow"""