On Fri, 28 Oct 2016, Thomas Gleixner wrote: > On Fri, 28 Oct 2016, Michal Necasek wrote: > > > > Sorry if I wasn't clear. No, it doesn't work for us. The ff8560512b8d > > commit fixes the APIC poking on machines where there is no local APIC > > available (and thus fixes the committer's machine), but it doesn't work > > in our case, where there is a local APIC but no I/O APIC, no ACPI MADT, > > and no MP tables. > > > In other words, for us boot_cpu_has(X86_FEATURE_APIC) is true but the > > APIC has not been set up yet because init_apic_mappings() hasn't been > > run.
Right. That mapping setup is an utter trainwreck as we do it from multiple places, but there is no reason why we can't move it before the call to prefill_possible_map(). Thanks, tglx diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index bbfbca5fea0c..b59fdba3cbdf 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -1221,11 +1221,13 @@ void __init setup_arch(char **cmdline_p) */ get_smp_config(); + /* Make sure apic is mapped before prefill_possible_map() */ + init_apic_mappings(); + prefill_possible_map(); init_cpu_to_node(); - init_apic_mappings(); io_apic_init_mappings(); kvm_guest_init();