xformers 0.13 does not seem to work for stable-baseline (at least AUTOMATIC1111) distribution. But 0.14.dev does work. We can fix it by
cd stable-diffusion-webui
python3 -m venv venv
source venv/bin/activate
pip install https://github.com/C43H66N12O12S2/stable-diffusion-webui/releases/download/linux/xformers-0.0.14.dev0-cp310-cp310-linux_x86_64.whl
deactivate