[patch 07/13] x2apic: use virtual wire A mode in disable_IO_APIC() with interrupt-remapping

Suresh Siddha
2009-03-17T00:31:23Z

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disable_IO_APIC() gets called during crashdump aswell, which configures the
IO-APIC/LAPIC so that legacy interrupts can be delivered for the kexec'd kernel.

In the presence of interrupt-remapping, we need to change the
interrupt-remapping configuration aswell as modifying IO-APIC for virtual wire
B mode.

To keep things simple during the crash, use virtual wire A mode
(for which we don't need to touch io-apic and interrupt-remapping tables).

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
---

Index: tip/arch/x86/kernel/apic/io_apic.c
===================================================================
--- tip.orig/arch/x86/kernel/apic/io_apic.c
+++ tip/arch/x86/kernel/apic/io_apic.c
@@ -2040,8 +2040,13 @@ void disable_IO_APIC(void)
* If the i8259 is routed through an IOAPIC
* Put that IOAPIC in virtual wire mode
* so legacy interrupts can be delivered.
+ *
+ * With interrupt-remapping, for now we will use virtual wire A mode,
+ * as virtual wire B is little complex (need to configure both
+ * IOAPIC RTE aswell as interrupt-remapping table entry).
+ * As this gets called during crash dump, keep this simple for now.
*/
- if (ioapic_i8259.pin != -1) {
+ if (ioapic_i8259.pin != -1 && !intr_remapping_enabled) {
struct IO_APIC_route_entry entry;

memset(&entry, 0, sizeof(entry));
@@ -2061,7 +2066,10 @@ void disable_IO_APIC(void)
ioapic_write_entry(ioapic_i8259.apic, ioapic_i8259.pin, entry);
}

- disconnect_bsp_APIC(ioapic_i8259.pin != -1);
+ /*
+ * Use virtual wire A mode when interrupt remapping is enabled.
+ */
+ disconnect_bsp_APIC(!intr_remapping_enabled && ioapic_i8259.pin != -1);
}

#ifdef CONFIG_X86_32

--