x86/irq: Store irq descriptor in vector array

We can spare the irq_desc lookup in the interrupt entry code if we
store the descriptor pointer in the vector array instead the interrupt
number.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Link: http://lkml.kernel.org/r/20150802203609.717724106@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 3 insertions, 1 deletions

diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 2165f45befff..47071a08bfa6 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -843,6 +843,7 @@ static struct irq_chip lguest_irq_controller = {
  */
 static int lguest_setup_irq(unsigned int irq)
 {
+        struct irq_desc *desc;
         int err;
 
         /* Returns -ve error or vector number. */
@@ -858,7 +859,8 @@ static int lguest_setup_irq(unsigned int irq)
                                       handle_level_irq, "level");
 
         /* Some systems map "vectors" to interrupts weirdly.  Not us! */
-        __this_cpu_write(vector_irq[FIRST_EXTERNAL_VECTOR + irq], irq);
+        desc = irq_to_desc(irq);
+        __this_cpu_write(vector_irq[FIRST_EXTERNAL_VECTOR + irq], desc);
         return 0;
 }