[Xen-devel] [PATCH 10 of 38] x86: add handle_irq() to allow interrupt injection

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

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@xxxxxxxxxx>
---
 arch/x86/include/asm/irq.h |    1 +
 arch/x86/kernel/irq_32.c   |   34 +++++++++++++++++++++-------------
 arch/x86/kernel/irq_64.c   |   27 ++++++++++++++++++---------
 3 files changed, 40 insertions(+), 22 deletions(-)

diff --git a/arch/x86/include/asm/irq.h b/arch/x86/include/asm/irq.h
--- a/arch/x86/include/asm/irq.h
+++ b/arch/x86/include/asm/irq.h
@@ -39,6 +39,7 @@
 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
--- a/arch/x86/kernel/irq_32.c
+++ b/arch/x86/kernel/irq_32.c
@@ -191,6 +191,26 @@
 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 @@
 {
        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
--- a/arch/x86/kernel/irq_64.c
+++ b/arch/x86/kernel/irq_64.c
@@ -42,6 +42,22 @@
 }
 #endif
 
+bool handle_irq(unsigned irq, struct pt_regs *regs)
+{
+       struct irq_desc *desc;
+
+#ifdef CONFIG_DEBUG_STACKOVERFLOW
+       stack_overflow_check(regs);
+#endif
+
+       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
@@ -50,7 +66,6 @@
 asmlinkage unsigned int 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;
@@ -58,16 +73,10 @@
 
        exit_idle();
        irq_enter();
+
        irq = __get_cpu_var(vector_irq)[vector];
 
-#ifdef CONFIG_DEBUG_STACKOVERFLOW
-       stack_overflow_check(regs);
-#endif
-
-       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();
 



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