Unable to determine the device handle for GPU 0000:02:00.0:UnKnow Error

I have a dual 2070 super machine。

this is my configuration
i7-9700K

Gigabyte C246-WU4
2* MSI RTX 2070 SUPER VENTUS OC 8G.
Now after booting, you can see the graphics card through nvidia-smi, but after a few minutes, the following error appears. Trouble pointing, thank you very much

Attach my bug report
nvidia-bug-report.log.gz (1.7 MB)

Aug 8 13:59:04 ubuntu kernel: [77546.475771] NVRM: Xid (PCI:0000:02:00): 79, pid=25366, GPU has fallen off the bus.

https://forums.developer.nvidia.com/t/gpu-fans-go-to-max-and-graphics-drivers-hang/222069/4?u=generix