The core identifier. ApicId can be divided into Physical ApicId and Logical ApicId.
The Physical ApicId is the value read from the LAPIC ID Register, while the Logical ApicId has different
encoding modes in XApic and X2Apic.
Indicates the IPI delivery status (read only), as follows:
0 (Idle) Indicates that this local APIC has completed sending any previous IPIs.
1 (Send Pending) Indicates that this local APIC has not completed sending the last IPI.
Indicates whether a shorthand notation is used to specify the destination of
the interrupt and, if so, which shorthand is used. Destination shorthands are
used in place of the 8-bit destination field, and can be sent by software
using a single write to the low doubleword of the ICR.