Note: This API calls are shared between DOS and Win16 personality.
DOSX is a specialized version of DPMI. Windows standard and extended mode kernel is a DPMI client app. Standard and extended mode kernel differs minimally and shares common codebase. Standard mode is just DPMI client, exnhanced mode is DPMI client running under Virtual Machime Manager. Both modes shares DPMI interface for kernel communication. The OS/2 virtual DOS Protected Mode Interface (VDPMI) device driver provides Version 0.9 DPMI support for virtual DOS machines. Win16 provides Version 1.0 DPMI support, but reported as 0.9.
Int 31H, AH=06H, AL=01H
Unlock Linear Region
AX = 0601H BX:CX = starting linear address of memory to unlock SI:DI = size of region to unlock (bytes)
if function successful Carry flag = clear if function unsuccessful Carry flag = set AX = error code 8002H invalid state (page not locked) 8025H invalid linear address (unallocated pages)
Unlocks a linear address range that was previously locked using the Lock Linear Region function (Int 31H Function 0600H).
If the function returns an error, none of the memory has been unlocked.
If the specified region overlaps part of a page at the beginning or end of the region, the page(s) will be unlocked.
A lock count is maintained for each locked page; the page is not unlocked until the lock count is decremented to zero (i.e. the number of Lock Region Int 31H Function 0600H calls has been balanced by the same number of Unlock Region Int 31H Function 0601H calls).
This function is ignored by DPMI implementations that do not support virtual memory; the function will return the Carry flag clear to indicate success, but has no other effect. DPMI hosts which support virtual memory may also choose to ignore this function, but such hosts must be able to handle page faults transparently at arbitrary points during a client's execution, including within interrupt and exception handlers.
Text based on http://www.delorie.com/djgpp/doc/dpmi/