Protected Mode Virtual Interrupts
The PVI feature was first implemented in the Pentium® processor. It was migrated backwards into the later versions of the 486 and is present in all IA32 processor subsequent to the Pentium®.
Refer to Figure 21-6 on page 497. With CR4[PVI] = 1 (PVI = Protected Mode Virtual Interrupt), if a Protected Mode application program (i.e., with a CPL of 3) attempts the execution of a CLI or an STI instruction it is handled in the same manner as a VM86 task if CR4[VME] = 1 (see “CLI Handling” on page 492 and “STI Handling” on page 495).
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