APIC-write VM exits are "trap-like": they save CS:RIP values for the
instruction after the write, and more importantly, the handler will
already see the new value in the virtual-APIC page. This means that
apic_reg_write cannot use kvm_apic_get_reg to omit timer cancelation
when mode changes.
timer_mode_mask shouldn't be changing as it depends on cpuid.
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>