Hi,

> so UBC mappings
> can only be accessed via fault-safe methods like uiomove().

Do I understand this correctly that the copyin/copyout (which is called
by uiomove to do the work) has to check the kernel address in addition
to the user address?  Yes, I know that most implementations will just
return EFAULT from copyin/copyout on any non-recoverable page fault, but
I thought this was only implementation laziness.

In case I understand this correctly, how are you going to return EIO
to the user in case of an I/O error and distinguish this from a "real"
EFAULT, given the current copyin/copyout implementations?

(If this is already taken care of in your implementation, I apologize,
but at the moment I'm unable to look into the repository :-(.)

Ciao,
Wolfgang
-- 
ws@TooLs.DE     (Wolfgang Solfrank, TooLs GmbH) 	+49-228-985800