I was on 2017.08 happily doing starx manually, when I rebased to 77c47c3ff8601da2fdc8f82f84be117dd636b02c (post 2018.05) and noticed that X11 was starting automatically due to S40xorg d83eacaaa8f17b5d573d540ca6338390fcfa0ba1

Unfortunately, the screen is then black.

However, if I manually remove S40xorg and go back to my startx method, it still works (except the mouse doesn't move, as before, do you have a clue about that as well?)

My precise setup is: https://github.com/cirosantilli/buildroot/tree/77c47c3ff8601da2fdc8f82f84be117dd636b02c which does for build:

#!/usr/bin/env bash
unset LD_LIBRARY_PATH
defconfig="${1:-qemu_x86_64_defconfig}"
outdir="output/${defconfig}"
make O="$outdir" "$defconfig"
printf "
BR2_CCACHE=y
BR2_PACKAGE_HOST_QEMU=y
BR2_PACKAGE_HOST_QEMU_LINUX_USER_MODE=n
BR2_PACKAGE_HOST_QEMU_SYSTEM_MODE=y
BR2_PACKAGE_HOST_QEMU_VDE2=y

BR2_PACKAGE_XAPP_TWM=y
BR2_PACKAGE_XAPP_XCALC=y
BR2_PACKAGE_XAPP_XCLOCK=y
BR2_PACKAGE_XAPP_XEYES=y
BR2_PACKAGE_XAPP_XINIT=y
BR2_PACKAGE_XDRIVER_XF86_INPUT_KEYBOARD=y
BR2_PACKAGE_XDRIVER_XF86_INPUT_MOUSE=y
BR2_PACKAGE_XDRIVER_XF86_VIDEO_CIRRUS=y
BR2_PACKAGE_XDRIVER_XF86_VIDEO_FBDEV=y
BR2_PACKAGE_XDRIVER_XF86_VIDEO_VESA=y
BR2_PACKAGE_XORG7=y
BR2_PACKAGE_XSERVER_XORG_SERVER=y
BR2_PACKAGE_XTERM=y
BR2_TOOLCHAIN_BUILDROOT_CXX=y
BR2_TOOLCHAIN_BUILDROOT_WCHAR=y
${2:-}
" >> "${outdir}/.config"
make O="$outdir" olddefconfig
time make O="$outdir" BR2_JLEVEL="$(nproc)" HOST_QEMU_OPTS='--enable-sdl --with-sdlabi=2.0'

run:

#!/usr/bin/env bash
outdir="${1:-output/qemu_x86_64_defconfig}"
"${outdir}/host/usr/bin/qemu-system-x86_64" \
  -M pc \
  -append 'root=/dev/vda console=ttyS0' \
  -drive file="${outdir}/images/rootfs.ext2,if=virtio,format=raw" \
  -enable-kvm \
  -kernel "${outdir}/images/bzImage" \
  -m 512 \
  -net nic,model=virtio \
  -net user,hostfwd=tcp::2222-:22 \
  -serial mon:stdio \
;