Right; GL/DX interoperability on all it's flavors isn't supported at CPU+GPU context (aka Shared Context)
This is a known issue; being evaludated for introduction at future versions;
We are very interested in getting an idea about what kind of usage you are seeking here with interop at Shared Context, can u please elaborate a little bit what usage is it targetting?
Right, resources as buffers/textures are phsyically shared by the context devices, CPU+GPU, in a Shared Context; Please note that u need to gauarantee alignments requirement according to the optimization guide for assuring physical sharing with the user hostptr (in case of CL_MEM_USE_HOST_PTR) in case its being provided.
This is doesn't necessarily mean that textures targetting GPU are managed less efficient comparing to single GPU context; Please notice that in case you have used hostptr at the texture creation which is aligned to 4K (see Intel OpenCL Optimization Guide) at Shared Context, then you have increased performance at clEnqueueMap/Unmap for the same texture.