https://github.com/AUTOMATIC1111/stable-diffusion-webui/discussions/5303#discussioncomment-4303079

Just follow the guide here,do exact same installations, and your xformers should work.

go to the webui directory

source ./venv/bin/activate

cd repositories

git clone https://github.com/facebookresearch/xformers.git

cd xformers

git submodule update --init --recursive

pip install -r requirements.txt

pip install -e .

The last step will take more time, so be patient.

特别是最后一句，要很久很久，真的很久。