linux-kernel - [PATCH 3.8 073/152] x86/apic: Disable I/O APIC before shutdown of the local APIC

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Message-Id: <1386371476-2477-74-git-send-email-kamal@canonical.com>
Date:	Fri,  6 Dec 2013 15:09:57 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Fenghua Yu <fenghua.yu@...el.com>, Ingo Molnar <mingo@...nel.org>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.8 073/152] x86/apic: Disable I/O APIC before shutdown of the local APIC

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

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

From: Fenghua Yu <fenghua.yu@...el.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@...el.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@...nel.org>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 arch/x86/kernel/crash.c  | 2 +-
 arch/x86/kernel/reboot.c | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index e0e0841..18677a9 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -127,12 +127,12 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
 	cpu_emergency_vmxoff();
 	cpu_emergency_svm_disable();
 
-	lapic_shutdown();
 #ifdef CONFIG_X86_IO_APIC
 	/* Prevent crash_kexec() from deadlocking on ioapic_lock. */
 	ioapic_zap_locks();
 	disable_IO_APIC();
 #endif
+	lapic_shutdown();
 #ifdef CONFIG_HPET_TIMER
 	hpet_disable();
 #endif
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 90fd119..44135ec 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -629,6 +629,10 @@ static void native_machine_emergency_restart(void)
 void native_machine_shutdown(void)
 {
 	/* Stop the cpus and apics */
+#ifdef CONFIG_X86_IO_APIC
+	disable_IO_APIC();
+#endif
+
 #ifdef CONFIG_SMP
 
 	/* The boot cpu is always logical cpu 0 */
@@ -657,10 +661,6 @@ void native_machine_shutdown(void)
 
 	lapic_shutdown();
 
-#ifdef CONFIG_X86_IO_APIC
-	disable_IO_APIC();
-#endif
-
 #ifdef CONFIG_HPET_TIMER
 	hpet_disable();
 #endif
-- 
1.8.3.2

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