x86: add handle_irq() to allow interrupt injection

Xen uses a different interrupt path, so introduce handle_irq() to
allow interrupts to be inserted into the normal interrupt path.  This
is handled slightly differently on 32 and 64-bit.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 38 insertions, 20 deletions

diff --git a/arch/x86/include/asm/irq.h b/arch/x86/include/asm/irq.h
index 592688ed04d3..d0f6f7d1771c 100644
--- a/arch/x86/include/asm/irq.h
+++ b/arch/x86/include/asm/irq.h
@@ -39,6 +39,7 @@ extern void fixup_irqs(void);
 extern unsigned int do_IRQ(struct pt_regs *regs);
 extern void init_IRQ(void);
 extern void native_init_IRQ(void);
+extern bool handle_irq(unsigned irq, struct pt_regs *regs);
 
 /* Interrupt vector management */
 extern DECLARE_BITMAP(used_vectors, NR_VECTORS);
diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c
index d802c844991e..61f09fb969ee 100644
--- a/arch/x86/kernel/irq_32.c
+++ b/arch/x86/kernel/irq_32.c
@@ -191,6 +191,26 @@ static inline int
 execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq) { return 0; }
 #endif
 
+bool handle_irq(unsigned irq, struct pt_regs *regs)
+{
+        struct irq_desc *desc;
+        int overflow;
+
+        overflow = check_stack_overflow();
+
+        desc = irq_to_desc(irq);
+        if (unlikely(!desc))
+                return false;
+
+        if (!execute_on_irq_stack(overflow, desc, irq)) {
+                if (unlikely(overflow))
+                        print_stack_overflow();
+                desc->handle_irq(irq, desc);
+        }
+
+        return true;
+}
+
 /*
  * do_IRQ handles all normal device IRQ's (the special
  * SMP cross-CPU interrupts have their own specific
@@ -200,31 +220,19 @@ unsigned int do_IRQ(struct pt_regs *regs)
 {
         struct pt_regs *old_regs;
         /* high bit used in ret_from_ code */
-        int overflow;
         unsigned vector = ~regs->orig_ax;
-        struct irq_desc *desc;
         unsigned irq;
 
-
         old_regs = set_irq_regs(regs);
         irq_enter();
         irq = __get_cpu_var(vector_irq)[vector];
 
-        overflow = check_stack_overflow();
-
-        desc = irq_to_desc(irq);
-        if (unlikely(!desc)) {
+        if (!handle_irq(irq, regs)) {
                 printk(KERN_EMERG "%s: cannot handle IRQ %d vector %#x cpu %d\n",
                                         __func__, irq, vector, smp_processor_id());
                 BUG();
         }
 
-        if (!execute_on_irq_stack(overflow, desc, irq)) {
-                if (unlikely(overflow))
-                        print_stack_overflow();
-                desc->handle_irq(irq, desc);
-        }
-
         irq_exit();
         set_irq_regs(old_regs);
         return 1;
diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
index 018963aa6ee3..a93f3b0dc7f2 100644
--- a/arch/x86/kernel/irq_64.c
+++ b/arch/x86/kernel/irq_64.c
@@ -48,6 +48,20 @@ static inline void stack_overflow_check(struct pt_regs *regs)
 #endif
 }
 
+bool handle_irq(unsigned irq, struct pt_regs *regs)
+{
+        struct irq_desc *desc;
+
+        stack_overflow_check(regs);
+
+        desc = irq_to_desc(irq);
+        if (unlikely(!desc))
+                return false;
+
+        generic_handle_irq_desc(irq, desc);
+        return true;
+}
+
 /*
  * do_IRQ handles all normal device IRQ's (the special
  * SMP cross-CPU interrupts have their own specific
@@ -56,7 +70,6 @@ static inline void stack_overflow_check(struct pt_regs *regs)
 asmlinkage unsigned int __irq_entry do_IRQ(struct pt_regs *regs)
 {
         struct pt_regs *old_regs = set_irq_regs(regs);
-        struct irq_desc *desc;
 
         /* high bit used in ret_from_ code  */
         unsigned vector = ~regs->orig_ax;
@@ -64,14 +77,10 @@ asmlinkage unsigned int __irq_entry do_IRQ(struct pt_regs *regs)
 
         exit_idle();
         irq_enter();
-        irq = __get_cpu_var(vector_irq)[vector];
 
-        stack_overflow_check(regs);
+        irq = __get_cpu_var(vector_irq)[vector];
 
-        desc = irq_to_desc(irq);
-        if (likely(desc))
-                generic_handle_irq_desc(irq, desc);
-        else {
+        if (!handle_irq(irq, regs)) {
                 if (!disable_apic)
                         ack_APIC_irq();