[PATCH 3.2 037/185] x86/apic: Disable I/O APIC before shutdown of the local APIC

Ben Hutchings
2013-12-29T02:08:43Z

From: Fenghua Yu <fenghua.yu@intel.com>

commit 522e66464467543c0d88d023336eec4df03ad40b upstream.

In reboot and crash path, when we shut down the local APIC, the I/O APIC is
still active. This may cause issues because external interrupts
can still come in and disturb the local APIC during shutdown process.

To quiet external interrupts, disable I/O APIC before shutdown local APIC.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1382578212-4677-1-git-send-email-fenghua.yu@intel.com
[ I suppose the 'issue' is a hang during shutdown. It's a fine change nevertheless. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/x86/kernel/crash.c | 2 +-
arch/x86/kernel/reboot.c | 8 ++++----
2 files changed, 5 insertions(+), 5 deletions(-)

--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -95,10 +95,10 @@ void native_machine_crash_shutdown(struc
cpu_emergency_vmxoff();
cpu_emergency_svm_disable();

- lapic_shutdown();
#if defined(CONFIG_X86_IO_APIC)
disable_IO_APIC();
#endif
+ lapic_shutdown();
#ifdef CONFIG_HPET_TIMER
hpet_disable();
#endif
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -652,6 +652,13 @@ void native_machine_shutdown(void)

/* The boot cpu is always logical cpu 0 */
int reboot_cpu_id = 0;
+#endif
+
+#ifdef CONFIG_X86_IO_APIC
+ disable_IO_APIC();
+#endif
+
+#ifdef CONFIG_SMP

#ifdef CONFIG_X86_32
/* See if there has been given a command line override */
@@ -675,10 +682,6 @@ void native_machine_shutdown(void)

lapic_shutdown();

-#ifdef CONFIG_X86_IO_APIC
- disable_IO_APIC();
-#endif
-
#ifdef CONFIG_HPET_TIMER
hpet_disable();
#endif