[PATCH] x86/apic: Disable I/O APIC before shutdown local APIC

[PATCH] x86/apic: Disable I/O APIC before shutdown local APIC

[Fenghua Yu]

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

In reboot and crash path, when shutdown local APIC, I/O APIC is still active.
This may cause issues because external interrupts can still come in and
disturb 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>
---
 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 7e920bf..618ce26 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -550,6 +550,10 @@ 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
 	/*
 	 * Stop all of the others. Also disable the local irq to
@@ -562,10 +566,6 @@ void native_machine_shutdown(void)
 
 	lapic_shutdown();
 
-#ifdef CONFIG_X86_IO_APIC
-	disable_IO_APIC();
-#endif
-
 #ifdef CONFIG_HPET_TIMER
 	hpet_disable();
 #endif
-- 
1.6.0.3

Re: [PATCH] x86/apic: Disable I/O APIC before shutdown local APIC

[Ingo Molnar]

* Fenghua Yu <fenghua.yu@intel.com> wrote:

> From: Fenghua Yu <fenghua.yu@intel.com>
> 
> In reboot and crash path, when shutdown local APIC, I/O APIC is still active.
> This may cause issues because external interrupts can still come in and
> disturb local APIC during shutdown process. To quiet external interrupts,
> disable I/O APIC before shutdown local APIC.

What specific 'issues' were observed, on what kind of systems?

Thanks,

	Ingo

RE: [PATCH] x86/apic: Disable I/O APIC before shutdown local APIC

[Yu, Fenghua]

> Ingo Molnar [mailto:mingo.kernel.org@gmail.com] wrote:
> Friday, October 25, 2013 3:58 AM
> 
> * Fenghua Yu <fenghua.yu@intel.com> wrote:
> 
> > From: Fenghua Yu <fenghua.yu@intel.com>
> >
> > In reboot and crash path, when shutdown local APIC, I/O APIC is still
> active.
> > This may cause issues because external interrupts can still come in
> and
> > disturb local APIC during shutdown process. To quiet external
> interrupts,
> > disable I/O APIC before shutdown local APIC.
> 
> What specific 'issues' were observed, on what kind of systems?
> 

This patch is a workaround for a to-be-published erratum; the erratum
will be published in a few weeks.

Thanks.

-Fenghua

[tip:x86/apic] x86/apic: Disable I/ O APIC before shutdown of the local APIC

[tip-bot for Fenghua Yu]

Commit-ID:  522e66464467543c0d88d023336eec4df03ad40b
Gitweb:     http://git.kernel.org/tip/522e66464467543c0d88d023336eec4df03ad40b
Author:     Fenghua Yu <fenghua.yu@intel.com>
AuthorDate: Wed, 23 Oct 2013 18:30:12 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 7 Nov 2013 10:12:37 +0100

x86/apic: Disable I/O APIC before shutdown of the local APIC

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
Cc: <stable@kernel.org>
[ I suppose the 'issue' is a hang during shutdown. It's a fine change nevertheless. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 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 7e920bf..618ce26 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -550,6 +550,10 @@ 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
 	/*
 	 * Stop all of the others. Also disable the local irq to
@@ -562,10 +566,6 @@ void native_machine_shutdown(void)
 
 	lapic_shutdown();
 
-#ifdef CONFIG_X86_IO_APIC
-	disable_IO_APIC();
-#endif
-
 #ifdef CONFIG_HPET_TIMER
 	hpet_disable();
 #endif