VMIRQD: A VxD that Virtualizes a Hardware Interrupt

Revised: February 1993

VMIRQD, the virtual monitor interrupt request (IRQ)
device, is a VxD that demonstrates the virtualization of a
hardware interrupt. This VxD declares a virtual device ID
number; see the VMIRQD.INC file for the declaration.
VMIRQD works only for unvirtualized IRQs. Most of the
hardware interrupts that Windows knows about (keyboard,
timer, mouse) use IRQs that are already virtualized, and
thus cannot be monitored by this VxD. For a simple
demonstration of VMIRQD, try IRQ6, the floppy controller
IRQ. This IRQ was not virtualized in the retail release of
Windows versions 3.0 and 3.1.

VMIRQD uses the following virtual machine manager (VMM)
and virtual programmable interrupt controller device
(VPICD) services:

>  _Get_Profile_Decimal_Int
>  Clear_Mono_Screen
>  Set_Mono_Cur_Pos
>  Out_Mono_String
>  _VPICD_Virtualize_IRQ
>  _VPICD_Phys_EOI


To build VMIRQD:
 
You will need Microsoft(R) Macro Assembler version 6.0 or
higher, as well as some special tools and include files;
see the "VxD Tools" and "VxD Include Files" abstracts to
copy these files to your development system. Configure
your development environment as described in the "VxD-Lite
Mini-DDK" technical article on the Microsoft Developer
Network CD.

If you have the Windows(TM) version 3.1 Device Driver Kit
(DDK), you can build its version of VMIRQD using the DDK-
supplied MASM5.EXE (a special version of Macro Assembler
version 5.10). Note that the DDK samples require a
specific structure for the source and include
subdirectories, whereas the corresponding samples in the
"VxD-Lite Mini-DDK" utilize the INCLUDE environment
variable to give you more flexibility in structuring your
development files.


To execute VMIRQD:

To use VMIRQD, you must have a secondary (monochrome)
monitor on your system.

1.  Place the following lines in the [386Enh] section of
your SYSTEM.INI file:

     DEBUGMONO=TRUE
     VMIRQD_IRQ=x

where x is the IRQ number you wish to monitor (try
floppy controller IRQ 6).

2.  Run VMIRQD.EXE from the MS-DOS(R) prompt before
starting Windows. When enhanced-mode Windows starts up,
the VxD will load automatically. Thus, you do not need to
modify the SYSTEM.INI file to load this VxD. VMIRQD will
automatically load each time you start Windows until you
reboot your computer; once rebooted, the stub loader is
cleared from memory and the VxD will not load.

If you prefer to have Windows load the VxD without first
executing it from the MS-DOS prompt, rename VMIRQD.EXE to
VMIRQD.386 and move it to the Windows SYSTEM subdirectory.
Add the line DEVICE=VMIRQD.386 to the [386Enh] section of
the SYSTEM.INI file.

3.  Run Windows in enhanced mode. The code responsible for
self-loading the VxD is in the VXDSTUB.ASM file and is
linked into the final VxD file by the STUB 'VXDSTUB.EXE'
module definition (.DEF) file statement. When executed
from the MS-DOS prompt, the VxDStub hooks Interrupt 2Fh,
terminates, and stays resident. When Microsoft Windows
initializes itself, the TSR responds to the Interrupt 2Fh,
AX=1605h broadcast and returns a structure that causes the
VxD to be loaded. This technique is discussed in the "TSR
Support in Microsoft Windows Version 3.1" technical
article on the Microsoft Developer Network CD.

VMIRQD was built and tested under Microsoft Windows
version 3.1 using Microsoft MASM versions 6.0 and 6.1 and
the tools and include files provided in the "VxD-Lite Mini-
DDK."

KEYWORDS: PR-CD1; CD3 (revised)

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