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@xxxxxxxxxxxxxx>
---
patch-2.6.26-rc1-20080505-mpparse-acpi-noirq0-2
diff -up --recursive --new-file linux-2.6.26-rc1-20080505.macro/arch/x86/kernel/mpparse.c linux-2.6.26-rc1-20080505/arch/x86/kernel/mpparse.c
--- linux-2.6.26-rc1-20080505.macro/arch/x86/kernel/mpparse.c 2008-05-05 02:56:19.000000000 +0000
+++ linux-2.6.26-rc1-20080505/arch/x86/kernel/mpparse.c 2008-06-30 21:53:33.000000000 +0000
@@ -50,6 +50,8 @@ static int mp_current_pci_id;
int pic_mode;
+int disable_irq0_through_ioapic __initdata;
+
/*
* Intel MP BIOS table parsing routines:
*/
@@ -887,6 +889,10 @@ void __init mp_override_legacy_irq(u8 bu
int ioapic = -1;
int pin = -1;
+ /* Skip the 8254 timer interrupt (IRQ 0) if requested. */
+ if (bus_irq == 0 && disable_irq0_through_ioapic)
+ return;
+
/*
* Convert 'gsi' to 'ioapic.pin'.
*/
@@ -955,6 +961,10 @@ void __init mp_config_acpi_legacy_irqs(v
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 mpc_config_intsrc *irq = mp_irqs + idx;
diff -up --recursive --new-file linux-2.6.26-rc1-20080505.macro/include/asm-x86/mpspec.h linux-2.6.26-rc1-20080505/include/asm-x86/mpspec.h
--- linux-2.6.26-rc1-20080505.macro/include/asm-x86/mpspec.h 2008-05-05 02:55:57.000000000 +0000
+++ linux-2.6.26-rc1-20080505/include/asm-x86/mpspec.h 2008-06-30 22:29:23.000000000 +0000
@@ -113,4 +113,15 @@ typedef struct physid_mask physid_mask_t
extern physid_mask_t phys_cpu_present_map;
+#ifdef CONFIG_X86_MPPARSE
+static inline void set_disable_irq0_through_ioapic(int v)
+{
+ extern int disable_irq0_through_ioapic;
+
+ disable_irq0_through_ioapic = v;
+}
+#else
+static inline void set_disable_irq0_through_ioapic(int v) { }
+#endif
+
#endif
--
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