_Simulate_VM_IO 


include vmm.inc

mov     edx, PortID
mov     ecx, IOType
mov     eax, OutputData
VMMCall _Simulate_VM_IO
mov     [InputData], eax

Reduces complex I/O instructions to simpler I/O operations. Uses EAX, flags.

PortID

Identifies the port for which input or output is simulated.

IOType

Specifies the type of I/O. It can be one of the following values:

Value

Meaning

Byte_Input

Inputs a single byte.

Byte_Output

Outputs a single byte.

Dword_Input

Inputs a doubleword.

Dword_Output

Outputs a doubleword.

Word_Input

Inputs a word.

Word_Output

Outputs a word.


OutputData

The data to be output. (This parameter is only used if the service is called to simulate output.)

This service is called to simulate port I/O from the current VM. It is useful for VxDs which need to alter the state of other VxDs. For example, a VxD could perform a simulated EOI by calling this procedure with: 


mov     al, 20h
mov     edx, 20h
mov     ecx, Byte_Output
VMMcall Simulate_VM_IO

Which is the same as a VM executing: 


mov     al, 20h
out         20h, al