APIC_VECTOR_MASK
highest = apic_ipltopri[ipl] + APIC_VECTOR_MASK;
highest = apic_ipltopri[ipl] + APIC_VECTOR_MASK;
(APIC_VECTOR_MASK | APIC_IPL_MASK);
highest = apic_ipltopri[pri] + APIC_VECTOR_MASK;
highest = apic_ipltopri[pri] + APIC_VECTOR_MASK;
highest = apic_ipltopri[ipl] + APIC_VECTOR_MASK;
vec = icrval & APIC_VECTOR_MASK;