x86/smpboot: Init apic mapping before usage

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 <[email protected]>
Reported-and-tested-by: Wolfgang Bauer <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: Borislav Petkov <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1610282114380.5053@nanos
Signed-off-by: Thomas Gleixner <[email protected]>

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index bbfbca5fea0cda10cf7f56e92d2a19d95a37ecb7..9c337b0e8ba7c4ac5b82a3e4ad979c7d4011b4bf 100644 (file)
--- 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();