ValueError: Unknown CUDA arch (8.6) or GPU not supported
when I build DCNv2 in my conda environment,I got this message.
I have checked cuda by nvidia-smi:
Tue Apr  6 20:03:13 2021       
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 460.67       Driver Version: 460.67       CUDA Version: 11.2     |
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|                               |                      |               MIG M. |
|===============================+======================+======================|
|   0  GeForce RTX 3070    Off  | 00000000:01:00.0  On |                  N/A |
|  0%   45C    P8    17W / 220W |    448MiB /  7979MiB |     23%      Default |
|                               |                      |                  N/A |
+-------------------------------+----------------------+----------------------+
                                                                               
+-----------------------------------------------------------------------------+
| Processes:                                                                  |
|  GPU   GI   CI        PID   Type   Process name                  GPU Memory |
|        ID   ID                                                   Usage      |
|=============================================================================|
|    0   N/A  N/A       955      G   /usr/lib/xorg/Xorg                 53MiB |
|    0   N/A  N/A      1555      G   /usr/lib/xorg/Xorg                210MiB |
|    0   N/A  N/A      1690      G   /usr/bin/gnome-shell               61MiB |
|    0   N/A  N/A      3564      G   ...AAAAAAAAA= --shared-files      108MiB |

and nvcc -V:
nvcc: NVIDIA (R) Cuda compiler driver
Copyright (c) 2005-2019 NVIDIA Corporation
Built on Sun_Jul_28_19:07:16_PDT_2019
Cuda compilation tools, release 10.1, V10.1.243

Any help?

Your GPU is &quot;too new&quot; for CUDA 10. Support for cards with compute capability 8.6 like yours was added in CUDA 11.1 (thank you @RobertCrovella for the correction). This means you'll need to use CUDA 11.1 or newer.
