xen: use our own eventchannel->irq path

Rather than overloading vectors for event channels, take full
responsibility for mapping an event channel to irq directly.  With
this patch Xen has its own irq allocator.

When the kernel gets an event channel upcall, it maps the event
channel number to an irq and injects it into the normal interrupt
path.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/include/asm/xen/events.h

@@ -15,10 +15,4 @@ static inline int xen_irqs_disabled(struct pt_regs *regs)
 	return raw_irqs_disabled_flags(regs->flags);
 }
 
-static inline void xen_do_IRQ(int irq, struct pt_regs *regs)
-{
-	regs->orig_ax = ~irq;
-	do_IRQ(regs);
-}
-
 #endif /* _ASM_X86_XEN_EVENTS_H */

arch/x86/xen/irq.c

@@ -19,21 +19,6 @@ void xen_force_evtchn_callback(void)
 	(void)HYPERVISOR_xen_version(0, NULL);
 }
 
-static void __init __xen_init_IRQ(void)
-{
-	int i;
-
-	/* Create identity vector->irq map */
-	for(i = 0; i < NR_VECTORS; i++) {
-		int cpu;
-
-		for_each_possible_cpu(cpu)
-			per_cpu(vector_irq, cpu)[i] = i;
-	}
-
-	xen_init_IRQ();
-}
-
 static unsigned long xen_save_fl(void)
 {
 	struct vcpu_info *vcpu;
@@ -127,7 +112,7 @@ static void xen_halt(void)
 }
 
 static const struct pv_irq_ops xen_irq_ops __initdata = {
-	.init_IRQ = __xen_init_IRQ,
+	.init_IRQ = xen_init_IRQ,
 
 	.save_fl = PV_CALLEE_SAVE(xen_save_fl),
 	.restore_fl = PV_CALLEE_SAVE(xen_restore_fl),

drivers/xen/events.c

@@ -30,6 +30,7 @@
 
 #include <asm/ptrace.h>
 #include <asm/irq.h>
+#include <asm/idle.h>
 #include <asm/sync_bitops.h>
 #include <asm/xen/hypercall.h>
 #include <asm/xen/hypervisor.h>
@@ -517,6 +518,24 @@ irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
 }
 
 
+static void xen_do_irq(unsigned irq, struct pt_regs *regs)
+{
+	struct pt_regs *old_regs = set_irq_regs(regs);
+
+	if (WARN_ON(irq == -1))
+		return;
+
+	exit_idle();
+	irq_enter();
+
+	//printk("cpu %d handling irq %d\n", smp_processor_id(), info->irq);
+	handle_irq(irq, regs);
+
+	irq_exit();
+
+	set_irq_regs(old_regs);
+}
+
 /*
  * Search the CPUs pending events bitmasks.  For each one found, map
  * the event number to an irq, and feed it into do_IRQ() for
@@ -557,8 +576,7 @@ void xen_evtchn_do_upcall(struct pt_regs *regs)
 				int port = (word_idx * BITS_PER_LONG) + bit_idx;
 				int irq = evtchn_to_irq[port];
 
-				if (irq != -1)
-					xen_do_IRQ(irq, regs);
+				xen_do_irq(irq, regs);
 			}
 		}