Guest Debugging Support
Many operating systems support an inter-machine debugging capability that uses a physical connection to support communication between a debugger that runs on the host operating system and the component that is being debugged that runs on the target operating system. The most common approach to make the physical connection is to use a NULL modem cable to connect a serial port on the host system to a serial port on the target system. Those ports are then used exclusively for debugging traffic. An alternative approach is to use an IEEE 1394 cable to connect the two systems. This section discusses both approaches, highlighting the differences where applicable.
When more than one guest might be debugged in this manner simultaneously, each partition's traffic must be multiplexed across the common physical connection. The hypervisor provides the Debugging Functions to exchange session-related data across the physical connection. The default port that is used for the connection is the serial COM port.
The hypervisor's debugging implementation is almost entirely protocol-independent. From the hypervisor's perspective, the debugging data is a sequenced stream of opaque data that is exchanged between the host and target operating systems over the connection. The exception to this sequenced stream is an additional multiplex message that translates into an NT kernel debugger break-in message for the client. Non-NT kernel debuggers do not need to handle this message for debugging to continue to work.
Note that because of the volatile nature of the connection, the hypervisor does not guarantee that any or all of the data will be delivered. The host and target systems should be aware of this fact and implement all appropriate synchronization and recovery mechanisms.
Note that the hypervisor must have guest debugging support enabled. The availability of the feature can be detected using a hypervisor CPUID leaf (for more information about this leaf, see CPUID Information Provided by the Hypervisor).
The following sections describe the hypervisor's support for the debugging of guest operating systems:
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Build date: 11/16/2013