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include vmm.inc
 
mov     esi, TaskSwitchCallback    ; points to callback procedure
VMMcall Call_When_Task_Switched
 
The Call_When_Task_Switched service installs a task-switched callback
procedure. The system calls this procedure whenever it carries out a task
switch. This service should be used sparingly and the callback procedure
should be optimized for speed.
 
Parameter           Description
────────────────────────────────────────────────────────────────────────────
 
TaskSwitchCallback  Points to the callback procedure to install. See the
                    Comments section for more information about the
                    procedure.
 
Return Value
 
This service has no return value.
 
Comments
 
Some virtual devices must save the state of a hardware device every time a
task switch occurs and restore the hardware state for the virtual machine
that is about to be run. However, virtual machine events can often be used
in place of using this service.
 
Virtual devices can install any number of callback procedures. The system
calls each one in the order installed, until all procedures have been
called.
 
The system calls the callback procedure as follows:
 
mov     eax, OldVM              ; previous VM handle
mov     ebx, VM                 ; current VM handle
call    [CritSecCallback]
 
The OldVM parameter specifies a handle identifying the previous virtual
machine (just prior to the task switch), and VM specifies a handle
identifying the current virtual machine.
 
The callback procedure can carry out any operation and can modify EAX, EBX,
ECX, EDX, ESI, EDI, and Flags.
 
Uses
 
Flags
 
See Also
 
Call_When_Idle, Call_When_Not_Critical
 
 
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