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

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Date:   Wed,  9 Nov 2016 11:45:41 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, prarit@...hat.com,
        ville.syrjala@...ux.intel.com, michael.thayer@...cle.com,
        knut.osmundsen@...cle.com, frank.mehnert@...cle.com,
        Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 4.8 058/138] x86/smpboot: Init apic mapping before usage

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

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

From: Thomas Gleixner <tglx@...utronix.de>

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@...cle.com>
Reported-and-tested-by: Wolfgang Bauer <wbauer@....at>
Cc: prarit@...hat.com
Cc: ville.syrjala@...ux.intel.com
Cc: michael.thayer@...cle.com
Cc: knut.osmundsen@...cle.com
Cc: frank.mehnert@...cle.com
Cc: Borislav Petkov <bp@...en8.de>
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1610282114380.5053@nanos
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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();