x86, ioapic, acpi: add a knob to disable IRQ 0 through I/O APIC
As discovered recently some systems exhibit problems when the 8254 timer
IRQ is routed through the I/O APIC. These problems do not affect the
timer IRQ itself and therefore cannot be detected when the correctness of
operation of the interrupt is verified in check_timer(). Therefore the
I/O APIC path of the timer IRQ has to be disabled entirely.
This is a change that lets platforms ask for the timer IRQ not to be
registered in the I/O APIC interrupt tables. The local APIC and ExtINTA
paths are unaffected. This request is only taken into account for ACPI
platforms as MP table systems seem unaffected so far.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 91bb9a9..92a5426 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -83,6 +83,8 @@
int acpi_ioapic;
int acpi_strict;
+static int disable_irq0_through_ioapic __initdata;
+
u8 acpi_sci_flags __initdata;
int acpi_sci_override_gsi __initdata;
int acpi_skip_timer_override __initdata;
@@ -992,6 +994,10 @@
int pin;
struct mp_config_intsrc mp_irq;
+ /* Skip the 8254 timer interrupt (IRQ 0) if requested. */
+ if (bus_irq == 0 && disable_irq0_through_ioapic)
+ return;
+
/*
* Convert 'gsi' to 'ioapic.pin'.
*/
@@ -1058,6 +1064,10 @@
for (i = 0; i < 16; i++) {
int idx;
+ /* Skip the 8254 timer interrupt (IRQ 0) if requested. */
+ if (i == 0 && disable_irq0_through_ioapic)
+ continue;
+
for (idx = 0; idx < mp_irq_entries; idx++) {
struct mp_config_intsrc *irq = mp_irqs + idx;