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Subject[PATCH][2.4.22-rc2] Disable APIC on reboot.
Here is a patch for 2.4.22-rc2 to disable the local APIC before
reboot. This fixes BIOS reboot problems reported by a few people.

disable_local_APIC() now checks if detect_init_APIC() enabled the
local APIC via the APIC_BASE MSR, and if so it now disables APIC_BASE.
Previously we would leave APIC_BASE enabled, and that made some
BIOSen unhappy.

The SMP reboot code calls disable_local_APIC(). On SMP HW there is
no change since detect_init_APIC() isn't called and APIC_BASE isn't
enabled by us. An SMP kernel on UP HW behaves just like an UP_APIC
kernel, so it disables APIC_BASE if we enabled it at boot.

The UP_APIC disable-before-suspend code is simplified since the existing
code to disable APIC_BASE is moved into disable_local_APIC().

(Felix Kühling originally reported the BIOS reboot problem. This is a
fixed-up version of his preliminary patch.)

/Mikael

--- linux-2.4.22-rc2/arch/i386/kernel/apic.c.~1~ 2003-06-14 13:30:19.000000000 +0200
+++ linux-2.4.22-rc2/arch/i386/kernel/apic.c 2003-08-11 23:42:39.000000000 +0200
@@ -38,6 +38,8 @@
int prof_old_multiplier[NR_CPUS] = { 1, };
int prof_counter[NR_CPUS] = { 1, };

+static int enabled_via_apicbase;
+
int get_maxlvt(void)
{
unsigned int v, ver, maxlvt;
@@ -142,6 +144,13 @@
value = apic_read(APIC_SPIV);
value &= ~APIC_SPIV_APIC_ENABLED;
apic_write_around(APIC_SPIV, value);
+
+ if (enabled_via_apicbase) {
+ unsigned int l, h;
+ rdmsr(MSR_IA32_APICBASE, l, h);
+ l &= ~MSR_IA32_APICBASE_ENABLE;
+ wrmsr(MSR_IA32_APICBASE, l, h);
+ }
}

/*
@@ -464,7 +473,6 @@

static void apic_pm_suspend(void *data)
{
- unsigned int l, h;
unsigned long flags;

if (apic_pm_state.perfctr_pmdev)
@@ -484,9 +492,6 @@
__save_flags(flags);
__cli();
disable_local_APIC();
- rdmsr(MSR_IA32_APICBASE, l, h);
- l &= ~MSR_IA32_APICBASE_ENABLE;
- wrmsr(MSR_IA32_APICBASE, l, h);
__restore_flags(flags);
}

@@ -636,6 +641,7 @@
l &= ~MSR_IA32_APICBASE_BASE;
l |= MSR_IA32_APICBASE_ENABLE | APIC_DEFAULT_PHYS_BASE;
wrmsr(MSR_IA32_APICBASE, l, h);
+ enabled_via_apicbase = 1;
}
}
/*
--- linux-2.4.22-rc2/arch/i386/kernel/process.c.~1~ 2003-08-11 21:27:40.000000000 +0200
+++ linux-2.4.22-rc2/arch/i386/kernel/process.c 2003-08-11 23:11:44.000000000 +0200
@@ -47,6 +47,7 @@
#ifdef CONFIG_MATH_EMULATION
#include <asm/math_emu.h>
#endif
+#include <asm/apic.h>

#include <linux/irq.h>

@@ -399,6 +400,14 @@
* other OSs see a clean IRQ state.
*/
smp_send_stop();
+#elif CONFIG_X86_LOCAL_APIC
+ if (cpu_has_apic) {
+ __cli();
+ disable_local_APIC();
+ __sti();
+ }
+#endif
+#ifdef CONFIG_X86_IO_APIC
disable_IO_APIC();
#endif

-
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