[tip:x86/urgent] x86/apic, doc: Justification for disabling IO APIC before Local APIC
Commit-ID: 2885432aaf15c1b7e65c787bfe7c5fec428296f0
Gitweb: http://git.kernel.org/tip/2885432aaf15c1b7e65c787bfe7c5fec428296f0
Author: Fenghua Yu
AuthorDate: Wed, 4 Dec 2013 16:07:49 -0800
Committer: H. Peter Anvin
CommitDate: Wed, 4 Dec 2013 19:33:21 -0800
x86/apic, doc: Justification for disabling IO APIC before Local APIC
Since erratum AVR31 in "Intel Atom Processor C2000 Product Family
Specification Update" is now published, I added a justification
comment for disabling IO APIC before Local APIC, as changed in commit:
522e66464467 x86/apic: Disable I/O APIC before shutdown of the local APIC
Signed-off-by: Fenghua Yu
Link:
http://lkml.kernel.org/r/1386202069-51515-1-git-send-email-fenghua...@intel.com
Signed-off-by: H. Peter Anvin
---
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
--
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[tip:x86/urgent] x86/apic, doc: Justification for disabling IO APIC before Local APIC
Commit-ID: 2885432aaf15c1b7e65c787bfe7c5fec428296f0
Gitweb: http://git.kernel.org/tip/2885432aaf15c1b7e65c787bfe7c5fec428296f0
Author: Fenghua Yu fenghua...@intel.com
AuthorDate: Wed, 4 Dec 2013 16:07:49 -0800
Committer: H. Peter Anvin h...@linux.intel.com
CommitDate: Wed, 4 Dec 2013 19:33:21 -0800
x86/apic, doc: Justification for disabling IO APIC before Local APIC
Since erratum AVR31 in Intel Atom Processor C2000 Product Family
Specification Update is now published, I added a justification
comment for disabling IO APIC before Local APIC, as changed in commit:
522e66464467 x86/apic: Disable I/O APIC before shutdown of the local APIC
Signed-off-by: Fenghua Yu fenghua...@intel.com
Link:
http://lkml.kernel.org/r/1386202069-51515-1-git-send-email-fenghua...@intel.com
Signed-off-by: H. Peter Anvin h...@linux.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
--
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