Is there a "Zero-Copy" equivalent in OpenCL? And how to use it in OpenCL?

In some cases it very useful to access the host memory from the gpu.

For example you need to read a large array only once and compare
the values with the array in the GPU memory and you don’t want
a copy of that data in GPU because of memory limitations.

This ist the case in which I plan to use “Zero-Copy”.

My use case is an iterative algorithm and I have to check whether there is
a change of the result or if the result is stable.

Is there something like “Zero-Copy” in OpenCL and how to use it?

Not currently. It could be added as an extension, possibly.

Any news on that?
I saw an asynchronus copy-compute example in the SDK but nothing on zero copy (or so i think).

See http://www.khronos.org/message_boards/viewtopic.php?f=28&t=2440

Also from http://blogs.amd.com/developer/2011/08/02/amd-app-sdk-2-5-provides-enhanced-performance-and-major-new-capabilities/

Transfers between CPUs and GPUs are improved for buffers declared with either the CL_MEM_USE_HOST_PTR or the CL_MEM_ALLOC_HOST_PTR flag.
For APUs, zero copy buffers created as CL_MEM_ALLOC_HOST_PTR | CL_MEM_READ_ONLY offer improved GPU read performance.