Copyout to XIO

[Matthew Dillon]

:Hi,
:
:I have a question regarding the use of XIO's. It seems that XIO's let
:a thread without process context read another processes's user buffer
:(which should be very handy), but there doesn't seem to be a way for
:that thread to write back into the process's address space, unless 
:that process happens to be switched in and we use copyout() the old
:fashioned way.
:
:How would a new-style device driver or filesystem implement READ for
:a user process from within its own thread?
:
:Thanks,
:Eric

    All device I/O is eventually going to be converted to a vm_page array
    on entry.  We're about half way along that goal.  Certain higher level
    system calls, such as read and write, will have to break large I/O's
    into smaller chunks that can be page-listed.

    The current use of alternative PMAPs to access another processes address
    space will eventually be removed, since its impossible to abstract
    that sort of access across a cluster.

					-Matt
					Matthew Dillon 
					<dillon at xxxxxxxxxxxxx>