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    Subject[PATCH 10 of 38] x86: add handle_irq() to allow interrupt injection
    Date
    From
    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>
    ---
    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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