From: "Fenghua Yu" <fenghua.yu@intel.com>
To: "Ingo Molnar" <mingo@elte.hu>,
"H. Peter Anvin" <hpa@linux.intel.com>,
"Thomas Gleixner" <tglx@linutronix.de>
Cc: "linux-kernel" <linux-kernel@vger.kernel.org>,
"x86" <x86@kernel.org>, "Fenghua Yu" <fenghua.yu@intel.com>
Subject: [PATCH] x86/apic: Justification for disabling IO APIC before Local APIC
Date: Wed, 4 Dec 2013 16:07:49 -0800
Message-ID: <1386202069-51515-1-git-send-email-fenghua.yu@intel.com> (raw)
From: Fenghua Yu <fenghua.yu@intel.com>
Since erratum AVR31 in "Intel Atom Processor C2000 Product Family
Specification Update" is published, I add a justification comment for
disabling IO APIC before Local APIC (commit 522e6646).
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
---
arch/x86/kernel/reboot.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index da3c599..c752cb4 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -558,6 +558,17 @@ void native_machine_shutdown(void)
{
/* Stop the cpus and apics */
#ifdef CONFIG_X86_IO_APIC
+ /*
+ * Disabling IO APIC before local APIC is a workaround for
+ * erratum AVR31 in "Intel Atom Processor C2000 Product Family
+ * Specification Update". In this situation, interrupts that target
+ * a Logical Processor whose Local APIC is either in the process of
+ * being hardware disabled or software disabled are neither delivered
+ * nor discarded. When this erratum occurs, the processor may hang.
+ *
+ * Even without the erratum, it still makes sense to quiet IO APIC
+ * before disabling Local APIC.
+ */
disable_IO_APIC();
#endif
--
1.8.1.2
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Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-05 0:07 Fenghua Yu [this message]
2013-12-05 3:36 ` [tip:x86/urgent] x86/apic, doc: " tip-bot for Fenghua Yu
2013-12-05 8:54 ` [PATCH] x86/apic: " Ingo Molnar
2013-12-05 13:27 ` Yu, Fenghua
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