glXCopyImage function

I need help to get work with glXCopyImageSubDataNV.
What I want to do is to copy a texture beyond different graphic boards with Linux. So I am trying to use glXCopyImageSubDataNV, but It does not seem work.
I am sure that the latest driver from nvidia is installed and opengl 3.2 is supported. I am almost sure that CreateContextAttribsARB is called as required.
The error is always BadMatch with glXVendorPrivate, even if unappropriate context or texture are quoted.
Did anyone tried this new function? I would appreciate if sample code is provided. If there is other ways to copy texture from one to other graphic
cards, the information would be most helpful.
Thank you in advance.

The problem resolved.
The cause was a simple careless mistake to generate texture with wrong context. I also found out that glXCreateContextAttribARB is not necessary, glxCreateContext is OK. The performance of glXCopyImage across two GPU is wonderful.
I am sorry for annoying you all. Thanks.

Very interesting. Thanks for letting us know.