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include vtd.inc
 
VxDcall VTD_Disable_Trapping
 
The VTD_Disable_Trapping service forces the VTD to stop I/O trapping on the
timer ports for a specified virtual machine. The VTD_Enable_Trapping service
must be called once for every call made to this service.
 
Parameter  Description
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EBX        Specifies a virtual machine handle.
 
Return Value
 
This service has no return value.
 
Comments
 
It is sometimes necessary to temporarily disable I/O trapping for virtual
machine code that reads the timer in extremely tight timing loops. A good
example is the hard disk BIOS code that reads the ports hundreds of times
per disk transfer. The overhead of servicing the I/O traps would cause disk
performance to slow to a crawl.
 
If this service is called N times, then VTD_Enable_Trapping must also be
called N times before trapping is re-enabled. This allows nested calls to
this service by more than one virtual device.
 
Uses
 
Flags
 
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