x86: I/O APIC: keep IRQ off when changing LVT registers

Disable the 8259A acting in the "virtual wire" mode to keep the interrupt
line inactive while fiddling with local APIC interrupt vector registers
associated with its destination inputs.  To be on the safe side,
especially concerning flipping the trigger mode.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/x86/kernel/io_apic_64.c b/arch/x86/kernel/io_apic_64.c
index 6433fc99f1f9..aa45a85c4d11 100644
--- a/arch/x86/kernel/io_apic_64.c
+++ b/arch/x86/kernel/io_apic_64.c
@@ -1702,7 +1702,9 @@ static inline void __init check_timer(void)
                         apic_printk(APIC_VERBOSE," works.\n");
                         nmi_watchdog_default();
                         if (nmi_watchdog == NMI_IO_APIC) {
+                                disable_8259A_irq(0);
                                 setup_nmi();
+                                enable_8259A_irq(0);
                         }
                         goto out;
                 }