x86/smpboot: Init apic mapping before usage

KAGA-KOKO · KAGA-KOKO · commit 1e90a13d0c3d · 2016-10-29T14:00:46.000+02:00
The recent changes, which forced the registration of the boot cpu on UP systems, which do not have ACPI tables, have been fixed for systems w/o local APIC, but left a wreckage for systems which have neither ACPI nor mptables, but the CPU has an APIC, e.g. virtualbox. The boot process crashes in prefill_possible_map() as it wants to register the boot cpu, which needs to access the local apic, but the local APIC is not yet mapped. There is no reason why init_apic_mapping() can't be invoked before prefill_possible_map(). So instead of playing another silly early mapping game, as the ACPI/mptables code does, we just move init_apic_mapping() before the call to prefill_possible_map(). In hindsight, I should have noticed that combination earlier. Sorry for the churn (also in stable)! Fixes: ff85605 ("x86/boot/smp: Don't try to poke disabled/non-existent APIC") Reported-and-debugged-by: Michal Necasek <michal.necasek@oracle.com> Reported-and-tested-by: Wolfgang Bauer <wbauer@tmo.at> Cc: prarit@redhat.com Cc: ville.syrjala@linux.intel.com Cc: michael.thayer@oracle.com Cc: knut.osmundsen@oracle.com Cc: frank.mehnert@oracle.com Cc: Borislav Petkov <bp@alien8.de> Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1610282114380.5053@nanos Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
@@ -1221,11 +1221,16 @@ void __init setup_arch(char **cmdline_p)
 	 */
 	get_smp_config();
 
+	/*
+	 * Systems w/o ACPI and mptables might not have it mapped the local
+	 * APIC yet, but prefill_possible_map() might need to access it.
+	 */
+	init_apic_mappings();
+
 	prefill_possible_map();
 
 	init_cpu_to_node();
 
-	init_apic_mappings();
 	io_apic_init_mappings();
 
 	kvm_guest_init();
