PAGE 58,132
;******************************************************************************
TITLE VITD - Virtual Interval Timer
;******************************************************************************
;
; (C) Copyright MICROSOFT Corp., 1991
;
; Title: VITD.ASM - Virtual Interval Timer
;
; Version: 3.00
;
; Date: 10-Jan-1991
;
; Author: Neil Sandlin
;
;
;------------------------------------------------------------------------------
;
; Change log:
;
; DATE REV DESCRIPTION
; ----------- --- -----------------------------------------------------------
;
;==============================================================================
.386p
;******************************************************************************
; I N C L U D E S
;******************************************************************************
.XLIST
INCLUDE VMM.Inc
INCLUDE Debug.Inc
INCLUDE VTD.Inc
INCLUDE ITIMER.Inc
.LIST
;******************************************************************************
; V I R T U A L D E V I C E D E C L A R A T I O N
;******************************************************************************
Declare_Virtual_Device VITD, 3, 0, VITD_Control, Undefined_Device_ID ,,,
;******************************************************************************
; I N I T D A T A
;******************************************************************************
VXD_IDATA_SEG
Begin_VxD_IO_Table VITD_IO_Table
VxD_IO ITIMER_Count, VITD_Count
VxD_IO ITIMER_State, VITD_State
End_VxD_IO_Table VITD_IO_Table
VXD_IDATA_ENDS
;******************************************************************************
; L O C A L D A T A
;******************************************************************************
VITD_CB_DATA STRUC
Timeout_Handle dd ?
Timeout_Start dd ?
Initial_Count dd ?
Current_Count dd ?
Access_byte db ?
Timer_State db ?
VITD_CB_DATA ENDS
VxD_LOCKED_DATA_SEG
VITD_CB_Offset dd 0
VITD_VMM_Min dd ?
VxD_LOCKED_DATA_ENDS
;******************************************************************************
; I N I T I A L I Z A T I O N C O D E
;******************************************************************************
VxD_ICODE_SEG
;******************************************************************************
;
; VITD_Sys_Crit_Init
;
; DESCRIPTION:
;
; This routine allocates space in the VM control block area for
; VM specific variables.
;
; ENTRY:
;
; EBX = Current VM Handle
;
;
;==============================================================================
BeginProc VITD_Sys_Crit_Init
push ebx
VMMCall _Allocate_Device_CB_Area, <<SIZE VITD_CB_DATA>, 0>
test eax, eax
jnz SHORT VITD_CB_OK
IFDEF DEBUG
Debug_Out "VITD: Allocate_Device_CB_Area failed"
ENDIF
VMMCall Fatal_Memory_Error
VITD_CB_OK:
mov [VITD_CB_Offset], eax
pop ebx
clc
ret
EndProc VITD_Sys_Crit_Init
;******************************************************************************
;
; VITD_Device_Init
;
; DESCRIPTION:
;
; This routine installs the I/O handlers for the virtual timer
; hardware.
;
; ENTRY:
;
; EBX = Current VM Handle
;
;==============================================================================
BeginProc VITD_Device_Init
VxDCall VTD_Get_Version
VxDCall VTD_Get_Interrupt_Period
IFDEF DEBUG
Trace_Out "VITD installed"
Trace_Out "Current interrupt rate=#EAX msecs. Min=#EBX, Max=#ECX"
ENDIF
mov VITD_VMM_Min, ebx ; save minimum interval
mov edi, OFFSET32 VITD_IO_Table
VMMCall Install_Mult_IO_Handlers
jnc SHORT DI_ok1
Trace_Out "VITD ERROR: installed only #ECX I/O handlers"
DI_ok1:
clc
ret
EndProc VITD_Device_Init
VxD_ICODE_ENDS
VxD_CODE_SEG
;******************************************************************************
;
; VITD_Create_VM
;
; DESCRIPTION:
;
; This routine initializes the virtual timer registers.
;
; ENTRY:
;
; EBX = Current VM Handle
;
;==============================================================================
BeginProc VITD_Create_VM
mov edi, ebx ; vm block
add edi, [VITD_CB_Offset] ; point to our area
mov [edi.Access_Byte], 0 ; initialize
mov [edi.Timer_State], ITIMER_STOPPED ; initial state
clc
ret
EndProc VITD_Create_VM
;******************************************************************************
;
; VITD_Destroy_VM
;
; DESCRIPTION:
;
; This routine has to cancel potential events on a destroyed VM.
;
; ENTRY:
;
; EBX = Current VM Handle
;
;==============================================================================
BeginProc VITD_Destroy_VM
mov edi, ebx ; vm block
add edi, [VITD_CB_Offset] ; point to our area
call VITD_Cancel ; cancel pending event, if any
vdm_exit:
clc
ret
EndProc VITD_Destroy_VM
VxD_CODE_ENDS
;******************************************************************************
VxD_LOCKED_CODE_SEG
;******************************************************************************
;
; VITD_Control
;
; DESCRIPTION:
;
; This is a call-back routine to handle the messages that are sent
; to VxD's to control system operation.
;
; ENTRY:
;
; EBX = Current VM Handle
;
;==============================================================================
BeginProc VITD_Control
Control_Dispatch Sys_Critical_Init, VITD_Sys_Crit_Init
Control_Dispatch Device_Init, VITD_Device_Init
Control_Dispatch Destroy_VM, VITD_Destroy_VM
Control_Dispatch Create_VM, VITD_Create_VM
clc
ret
EndProc VITD_Control
VxD_LOCKED_CODE_ENDS
VxD_CODE_SEG
;******************************************************************************
;
; VITD_Count
;
; DESCRIPTION:
;
; This routine handles byte I/O to the virtual count register.
; The basic algorithm is as follows:
;
; if I/O is a read ( IN al,countport )
; get access byte
; if Timer is active and reading first byte
; decrement count by elapsed time
; return Current_Count[access_byte]
;
; else if I/O is a write ( OUT countport,al )
; get access byte
; if Timer NOT active
; save Count[access_byte]
;
; ENTRY:
;
; EBX = Current VM Handle
; ECX = Type of I/O
; EDX = Port number
; EBP-> Client register structure
;
;******************************************************************************
BeginProc VITD_Count
mov edi, ebx ; vm block
add edi, [VITD_CB_Offset] ; point to our area
Dispatch_Byte_IO Fall_Through, <SHORT vitc_Out>
;---------------------------------------------------------------------
; Handle Read Count Port
;---------------------------------------------------------------------
call Update_Access_Byte ; load ECX with index
or ecx, ecx ; first byte?
jnz SHORT vitc_no_adjust
test [edi.Timer_State], ITIMER_RUNNING ; timer pending?
jz SHORT vitc_no_adjust ; no, don't update
VMMCall Get_VM_Exec_Time ; get current time
sub eax, [edi.Timeout_Start] ; now have elapsed time
mov ebx, [edi.Initial_Count] ; get original count
sub ebx, eax ; now have new count
mov [edi.Current_Count], ebx ; save it for output
vitc_no_adjust:
mov eax, [edi.Current_Count] ; get entire count
shl ecx, 3 ; multipy index by 8
shr eax, cl ; now have byte in al
ret
;---------------------------------------------------------------------
; Handle Write Count Port
;---------------------------------------------------------------------
vitc_Out:
call Update_Access_Byte ; load ECX with index
test [edi.Timer_State], ITIMER_RUNNING ; timer pending?
jnz SHORT vitc_ro ; yes, count is R/O
mov BYTE PTR [edi.Initial_Count+ecx], al ; save count
mov BYTE PTR [edi.Current_Count+ecx], al ; save count
vitc_ro:
ret
EndProc VITD_Count
;******************************************************************************
;
; Update_Access_Byte
;
; DESCRIPTION:
;
; When a VM does I/O to the virtual count register, it has to
; do it a byte at a time. This routine updates the byte index
; into the 4 byte register, so that each byte I/O accesses the
; next byte. The register is programmed starting from the lowest
; significant byte to the highest.
;
;
; ENTRY:
;
;
;******************************************************************************
BeginProc Update_Access_Byte
movzx ecx, [edi.Access_Byte] ; get byte to retrieve
cmp ecx, 3 ; will increment wrap?
jb SHORT vitc_go1 ; no
mov [edi.Access_Byte], 0 ; initialize
jmp SHORT vitc_go2 ; no
vitc_go1:
inc [edi.Access_Byte] ; for next time
vitc_go2:
ret
EndProc Update_Access_Byte
;******************************************************************************
;
; VITD_State
;
; DESCRIPTION:
;
; This routine handles byte I/O to the virtual state register.
; The basic algorithm is as follows:
;
; if I/O is a read ( IN al,stateport )
; return State
;
; else if I/O is a write ( OUT stateport,al )
; if Timer_Start requested
; if Timer NOT running
; save new state
; if Enhanced requested
; Start enhanced VMM state
; Set up VM Timeout
; save handle and start time
;
; else /* Timer Stop requested */
; if Timer running
; Cancel previous timer request
; save new state
;
;
; ENTRY:
;
; EBX = Current VM Handle
; ECX = Type of I/O
; EDX = Port number
; EBP-> Client register structure
;
;******************************************************************************
BeginProc VITD_State
mov edi, ebx ; vm block
add edi, [VITD_CB_Offset] ; point to our area
Dispatch_Byte_IO Fall_Through, <SHORT vits_Out>
;---------------------------------------------------------------------
; Handle Read State port
;---------------------------------------------------------------------
movzx eax, [edi.Timer_State] ; get state
ret
vits_Out:
;---------------------------------------------------------------------
; Handle Write State port
;---------------------------------------------------------------------
test eax, ITIMER_RUNNING ; Start timer request?
jz SHORT vits_stop_timer ; no
test [edi.Timer_State], ITIMER_RUNNING ; timer pending?
jnz SHORT vits_exit ; yes, state is R/O
mov [edi.Timer_State], al ; save state
test eax, ITIMER_ENHANCED ; going for accuracy?
jz SHORT vits_noenh ; no
mov eax, VITD_VMM_Min ; get minimum
VxDCall VTD_Begin_Min_Int_Period ; ok, here we go
vits_noenh:
mov eax, [edi.Initial_Count] ; get msecs to wait
mov esi, OFFSET32 VITD_Timeout_Proc
xor edx, edx ; ref data
VMMCall Set_VM_Time_Out ; start timer running
or esi, esi ; was timeout not scheduled?
jz SHORT vits_abort ; hmmm...
mov [edi.Timeout_Handle], esi ; save handle
VMMCall Get_VM_Exec_Time ; remember the start
mov [edi.Timeout_Start], eax ; for later
IFDEF DEBUG
VxDCall VTD_Get_Interrupt_Period
Trace_Out "VITD Start: VM=#EBX, rate=#EAX msecs"
ENDIF
vits_exit:
ret
vits_abort:
mov [edi.Timer_State], ITIMER_ERROR ; woops...
ret
vits_stop_timer:
test [edi.Timer_State], ITIMER_RUNNING ; timer pending?
jz SHORT vits_svst ; no event to cancel
call VITD_Cancel ; cancel pending event, if any
vits_svst:
mov [edi.Timer_State], al ; save new state
ret
EndProc VITD_State
;******************************************************************************
;
; VITD_Cancel
;
; DESCRIPTION:
;
; This routine will cancel a previous Timeout request made, if any.
; It is called if the VM stops the timer manually, or if the VM
; is destroyed.
;
; ENTRY:
;
; EBX = Current VM Handle
; EDI-> VITD CB area
;
;******************************************************************************
BeginProc VITD_Cancel
test [edi.Timer_State], ITIMER_RUNNING ; timer pending?
jz SHORT vcnl_exit ; no
mov esi, [edi.Timeout_Handle] ; get handle
VMMCall Cancel_Time_Out ; cancel it
test [edi.Timer_State], ITIMER_ENHANCED ; going for accuracy?
jz SHORT vcnl_exit ; no
mov eax, VITD_VMM_Min ; get minimum
VxDCall VTD_End_Min_Int_Period ; cancel min int
vcnl_exit:
IFDEF DEBUG
VxDCall VTD_Get_Interrupt_Period
Trace_Out "VITD Cancel: VM=#EBX, rate=#EAX msecs"
ENDIF
ret
EndProc VITD_Cancel
;******************************************************************************
;
; VITD_Timeout_Proc
;
; DESCRIPTION:
;
; This routine is called by VMM when the requested time has
; elapsed in the virtual machine. The routine cancels the enhanced
; interval period, if it was in effect, updates the count, and
; queues an event to call VITD_Reflect_Int. Most likely, the
; Reflect_Int routine will be called immediately, because we
; are already in the VM we want. But, to be safe, the routine
; will not be called until the VM has enabled for interrupts
; and is not in a critical section.
;
; ENTRY:
;
; EBX = current VM (VM time-out was scheduled for)
; ECX = Number of EXTRA milleseconds that have elapsed
; EDX = Reference Data (0)
; EBP-> Client register structure
;
;******************************************************************************
BeginProc VITD_Timeout_Proc
mov edi, ebx ; vm block
add edi, [VITD_CB_Offset] ; point to our area
test [edi.Timer_State], ITIMER_ENHANCED ; going for accuracy?
jz SHORT vtmo_noenh ; no
mov eax, VITD_VMM_Min ; get minimum
VxDCall VTD_End_Min_Int_Period ; cancel min int
vtmo_noenh:
xor eax, eax ; clear
sub eax, ecx ; now has overrun count
mov [edi.Current_Count], eax ; save here
test [edi.Timer_State], ITIMER_NO_RUPT ; test to send rupt?
mov [edi.Timer_State], ITIMER_STOPPED ; and clear state
jnz SHORT vtmo_norupt ; no rupt needed
xor eax, eax ; no boost
mov ecx, PEF_Wait_For_STI or PEF_Wait_Not_Crit ; better wait
mov edx, edi ; pointer to CB area
mov esi, OFFSET32 VITD_Reflect_Int
VMMCall Call_Priority_VM_Event ; do it
vtmo_norupt:
IFDEF DEBUG
VxDCall VTD_Get_Interrupt_Period
Trace_Out "VITD Stop: VM=#EBX, rate=#EAX msecs"
ENDIF
ret
EndProc VITD_Timeout_Proc
;******************************************************************************
;
; VITD_Reflect_Int
;
; DESCRIPTION:
;
; This routine is called to simulate an interval timer interrupt
; into the current VM.
;
; ENTRY:
;
; EBX = current VM (VM time-out was scheduled for)
; EDX-> VITD CB area
; EBP-> Client register structure
;
;******************************************************************************
BeginProc VITD_Reflect_Int
mov edi, edx ; our CB area
VMMCall Begin_Nest_Exec ; ready to call VM
mov eax, ITIMER_VECTOR ; get interrupt vector
VMMCall Exec_Int ; reflect
VMMCall End_Nest_Exec ; that's it
ret
EndProc VITD_Reflect_Int
VxD_CODE_ENDS
END
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