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Subject[PATCH] [7/7] Don't disable the APIC if it hasn't been mapped yet
Date

When the kernel panics early for some unrelated reason
there would be eventually an early exception inside panic because
clear_local_APIC tried to disable the not yet mapped APIC.
Check for that explicitely.

Signed-off-by: Andi Kleen <ak@suse.de>

---
arch/x86/kernel/apic_32.c | 11 ++++++++---
arch/x86/kernel/apic_64.c | 9 +++++++--
2 files changed, 15 insertions(+), 5 deletions(-)

Index: linux/arch/x86/kernel/apic_32.c
===================================================================
--- linux.orig/arch/x86/kernel/apic_32.c
+++ linux/arch/x86/kernel/apic_32.c
@@ -99,6 +99,8 @@ static DEFINE_PER_CPU(struct clock_event
/* Local APIC was disabled by the BIOS and enabled by the kernel */
static int enabled_via_apicbase;

+static unsigned long apic_phys;
+
/*
* Get the LAPIC version
*/
@@ -616,9 +618,14 @@ int setup_profiling_timer(unsigned int m
*/
void clear_local_APIC(void)
{
- int maxlvt = lapic_get_maxlvt();
+ int maxlvt;
u32 v;

+ /* APIC hasn't been mapped yet */
+ if (!apic_phys)
+ return;
+
+ maxlvt = lapic_get_maxlvt();
/*
* Masking an LVT entry can trigger a local APIC error
* if the vector is zero. Mask LVTERR first to prevent this.
@@ -1105,8 +1112,6 @@ no_apic:
*/
void __init init_apic_mappings(void)
{
- unsigned long apic_phys;
-
/*
* If no local APIC can be found then set up a fake all
* zeroes page to simulate the local APIC and another
Index: linux/arch/x86/kernel/apic_64.c
===================================================================
--- linux.orig/arch/x86/kernel/apic_64.c
+++ linux/arch/x86/kernel/apic_64.c
@@ -81,6 +81,8 @@ static struct clock_event_device lapic_c
};
static DEFINE_PER_CPU(struct clock_event_device, lapic_events);

+static unsigned long apic_phys;
+
/*
* Get the LAPIC version
*/
@@ -516,6 +518,11 @@ void clear_local_APIC(void)
int maxlvt = lapic_get_maxlvt();
u32 v;

+ /* APIC hasn't been mapped yet */
+ if (!apic_phys)
+ return;
+
+ maxlvt = lapic_get_maxlvt();
/*
* Masking an LVT entry can trigger a local APIC error
* if the vector is zero. Mask LVTERR first to prevent this.
@@ -850,8 +857,6 @@ static int __init detect_init_APIC(void)
*/
void __init init_apic_mappings(void)
{
- unsigned long apic_phys;
-
/*
* If no local APIC can be found then set up a fake all
* zeroes page to simulate the local APIC and another

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