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

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Message-ID: <lsq.1388282923.103489079@decadent.org.uk>
Date:	Sun, 29 Dec 2013 03:08:43 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Ingo Molnar" <mingo@...nel.org>,
	"Fenghua Yu" <fenghua.yu@...el.com>
Subject: [PATCH 3.2 037/185] x86/apic: Disable I/O APIC before shutdown of
 the local APIC

3.2.54-rc1 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>
---
 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

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