CPUs are limited in the number of interrupts they can have affined to them

Issue

• How many interrupts can be assigned (pinned) to a CPU core?
• Why it is not possible to assign more than X number of IRQs to a CPU?
• Why CPU N does not "accept" one more IRQ through smp_affinity or smp_affinity_list proc-fs interface?
• The message like irq XYZ: Affinity broken due to vector space exhaustion can appear in kernel log (since RHEL 8.3 release and later).