one-sided transfer for arrays

[canonizer]

sometimes, arrays are used for one-sided communication only, e.g. device -> host or host -> device. As they can be still modified on both sides, however, general way of handling them will require copying in both directions. It is possible, though, to add a flag indicating that arrays are copied one side only:

GPUVM_HOST_TO_DEVICE // copied host -> device
GPUVM_DEVICE_TO_HOST // copied device -> host

...
gpuvm_link(harr, sz, idev, darr, GPUVM_ON_HOST | GPUVM_HOST_TO_DEVICE);