Enable WinDbg in Vista or later OS version

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Kernel-mode code can use the DbgPrintEx and KdPrintEx routines to send a messages to the kernel debugger that are only transmitted under certain conditions. This allows you to filter out messages that you are not interested in.

Note In Windows Server 2003 and earlier versions of Windows, DbgPrint and KdPrint send messages to the kernel debugger unconditionally. In Windows Vista and later versions of Windows, these routines send messages conditionally, like DbgPrintEx and KdPrintEx. Whichever version of Windows you are using, it is recommended that you use DbgPrintEx and KdPrintEx, since these allow you to control the conditions under which the message will be sent.

The basic procedure is as follows:

To filter debugging messages
For each message you wish to send to the debugger, use the function DbgPrintEx or KdPrintEx in your driver's code. Pass the appropriate component name to the ComponentId parameter, and pass a value to the Level parameter that reflects the severity or nature of this message. The message itself is passed to the Format and arguments parameters as with printf.
Set the value of the appropriate component filter mask. Each component has a different mask; the mask value indicates which of that component's messages will be displayed. The component filter mask may be set in the registry using a registry editor, or in memory using a kernel debugger.
Attach a kernel debugger to the computer. Each time your driver passes a message to DbgPrintEx or KdPrintEx, the values passed to ComponentId and Level will be compared with the value of the corresponding component filter mask. If these values satisfy certain criteria, the message will be sent to the kernel debugger and displayed. Otherwise, no message will be sent.

There are two ways to set a component filter mask:

The component filter mask can be accessed in the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Debug Print Filter. Using a registry editor, create or open this key. Under this key, create a value with the name of the desired component, in uppercase. Set it equal to the DWORD value that you wish to use as the component filter mask.
If a kernel debugger is active, it can access the component filter mask value by dereferencing the address stored in the symbol Kd_XXXX_Mask, where XXXX is the desired component name. You can display the value of this mask in WinDbg or KD with the dd (Display DWORD) command, or enter a new component filter mask with the ed (Enter DWORD) command. If there is a danger of symbol ambiguity, you may wish to specify this symbol as nt!Kd_XXXX_Mask.

Enable DebugPrint message in WinDbg
ed Kd_DEFAULT_Mask 0x7ff ( to enable default dbgprint or kdPrint)
ed Kd_IHVDRIVER_Mask 0x7ff ( to enable default dbgprint or kdPrint)

Enable DebugPrint message in Registry key
• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Debug Print Filter. Create DWORD DEFAULT VALUE “0X7FF”;