Each Task (including the OS) Has Its Own TSS
When a task switch occurs, the processor automatically loads its segment registers with the values from the new task's TSS. The GDTR register is not loaded with a new value, however. This means that all tasks share the same GDT, but each can select a different set of segment descriptors within the GDT when it is started or resumed (via a task switch).
Switch to an Application Task
If the new task is an application program, the value loaded into the CS register from its TSS selects a code segment descriptor with a DPL of 3. This means the CPL of the task is 3.
A new value is also loaded into CR3, selecting the Page Directory used while the application task is executing. The task's Page Directory and ...
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