[PATCH 4.8 058/138] x86/smpboot: Init apic mapping before usage

[Greg Kroah-Hartman]

4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

commit 1e90a13d0c3dc94512af1ccb2b6563e8297838fa upstream.

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: ff8560512b8d ("x86/boot/smp: Don't try to poke disabled/non-existent APIC")
Reported-and-debugged-by: Michal Necasek <michal.necasek@xxxxxxxxxx>
Reported-and-tested-by: Wolfgang Bauer <wbauer@xxxxxx>
Cc: prarit@xxxxxxxxxx
Cc: ville.syrjala@xxxxxxxxxxxxxxx
Cc: michael.thayer@xxxxxxxxxx
Cc: knut.osmundsen@xxxxxxxxxx
Cc: frank.mehnert@xxxxxxxxxx
Cc: Borislav Petkov <bp@xxxxxxxxx>
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1610282114380.5053@nanos
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/x86/kernel/setup.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1222,11 +1222,16 @@ void __init setup_arch(char **cmdline_p)
 	if (smp_found_config)
 		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();