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    Subject[004/129] xen: use percpu interrupts for IPIs and VIRQs
    2.6.35-stable review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

    commit aaca49642b92c8a57d3ca5029a5a94019c7af69f upstream.

    IPIs and VIRQs are inherently per-cpu event types, so treat them as such:
    - use a specific percpu irq_chip implementation, and
    - handle them with handle_percpu_irq

    This makes the path for delivering these interrupts more efficient
    (no masking/unmasking, no locks), and it avoid problems with attempts
    to migrate them.

    Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    drivers/xen/events.c | 19 +++++++++++++++----
    1 file changed, 15 insertions(+), 4 deletions(-)

    --- a/drivers/xen/events.c
    +++ b/drivers/xen/events.c
    @@ -107,6 +107,7 @@ static inline unsigned long *cpu_evtchn_
    #define VALID_EVTCHN(chn) ((chn) != 0)

    static struct irq_chip xen_dynamic_chip;
    +static struct irq_chip xen_percpu_chip;

    /* Constructor for packed IRQ information. */
    static struct irq_info mk_unbound_info(void)
    @@ -389,8 +390,8 @@ static int bind_ipi_to_irq(unsigned int
    if (irq < 0)
    goto out;

    - set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,
    - handle_level_irq, "ipi");
    + set_irq_chip_and_handler_name(irq, &xen_percpu_chip,
    + handle_percpu_irq, "ipi");

    bind_ipi.vcpu = cpu;
    if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_ipi,
    @@ -430,8 +431,8 @@ static int bind_virq_to_irq(unsigned int

    irq = find_unbound_irq();

    - set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,
    - handle_level_irq, "virq");
    + set_irq_chip_and_handler_name(irq, &xen_percpu_chip,
    + handle_percpu_irq, "virq");

    evtchn_to_irq[evtchn] = irq;
    irq_info[irq] = mk_virq_info(evtchn, virq);
    @@ -934,6 +935,16 @@ static struct irq_chip xen_dynamic_chip
    .retrigger = retrigger_dynirq,
    };

    +static struct irq_chip en_percpu_chip __read_mostly = {
    + .name = "xen-percpu",
    +
    + .disable = disable_dynirq,
    + .mask = disable_dynirq,
    + .unmask = enable_dynirq,
    +
    + .ack = ack_dynirq,
    +};
    +
    void __init xen_init_IRQ(void)
    {
    int i;



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