If Kernel doesn't support x2apic , what can user do in BIOS settings?

For some older hypervisor or operating system that is not compatible with x2APIC support, user may got kernel panic if x2apic was enabled in BIOS but kernel does not support it. 

It's the option for processor x2APIC Support. When this was enabled in BIOS processor x2APIC support helps operating systems run more efficiently on high core count configurations and optimizes interrupt distribution in virtualized environments.

Kernel panic - not syncing: BIOS has enabled x2apic but kernel doesn't support x2apic, please disable x2apic in BIOS.

User can disable x2apic support by disabling VT-d in BIOS setup menu