linux-kernel - [PATCH 3.4 132/214] x86/apic: Disable I/O APIC before shutdown of the local APIC

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Date:	Wed,  4 Jun 2014 21:18:15 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Fenghua Yu <fenghua.yu@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	Ben Hutchings <ben@...adent.org.uk>,
	Rui Xiang <rui.xiang@...wei.com>
Subject: [PATCH 3.4 132/214] x86/apic: Disable I/O APIC before shutdown of the local APIC

3.4-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>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Cc: Rui Xiang <rui.xiang@...wei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kernel/crash.c  |    2 +-
 arch/x86/kernel/reboot.c |   11 +++++++----
 2 files changed, 8 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
@@ -668,6 +668,13 @@ 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 */
@@ -691,10 +698,6 @@ void native_machine_shutdown(void)

 	lapic_shutdown();

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

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