Note: This API calls are shared between DOS and Win16 personality.
DPMI is a shared interface for DOS applications to access Intel 80286+ CPUs services. DOS DMPI host provides core services for protected mode applications. Multitasking OS with DOS support also provides DMPI in most cases. Windows standard and extended mode kernel is a DPMI client app. Standard and extended mode kernel differs minimally and shares common codebase. Standard Windows kernel works under DOSX extender. DOSX is a specialized version of 16-bit DPMI Extender (but it is standard DPMI host). Standard mode is just DPMI client, exnhanced mode is DPMI client running under Virtual Machime Manager (really, multitasker which allow to run many DOS sessions). 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 (up to Windows ME) provides Version 0.9 DPMI support.
DPMI host often merged with DPMI extender. Usually DPMI extender provide DPMI host standard services and DOS translation or True DPMI services.
Int 31H, AH=09H, AL=02H
Get Virtual Interrupt State
AX = 0902H
Carry flag = clear (this function always succeeds) AL = 0 if virtual interrupts are disabled AL = 1 if virtual interrupts are enabled
This function should be used in preference to the PUSHF instruction to examine the interrupt flag, because the PUSHF instruction returns the physical interrupt flag rather than the virtualized (per-client) interrupt flag. On some DPMI hosts, the physical interrupt flag will always be enabled, even when hardware interrupts are not being passed through to the client.
Text based on http://www.delorie.com/djgpp/doc/dpmi/