smp.c

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/*
 * Xen SMP support
 *
 * This file implements the Xen versions of smp_ops.  SMP under Xen is
 * very straightforward.  Bringing a CPU up is simply a matter of
 * loading its initial context and setting it running.
 *
 * IPIs are handled through the Xen event mechanism.
 *
 * Because virtual CPUs can be scheduled onto any real CPU, there's no
 * useful topology information for the kernel to make use of.  As a
 * result, all CPUs are treated as if they're single-core and
 * single-threaded.
 */
#include <linux/sched.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/smp.h>
#include <linux/irq_work.h>

#include <asm/paravirt.h>
#include <asm/desc.h>
#include <asm/pgtable.h>
#include <asm/cpu.h>

#include <xen/interface/xen.h>
#include <xen/interface/vcpu.h>

#include <asm/xen/interface.h>
#include <asm/xen/hypercall.h>

#include <xen/xen.h>
#include <xen/page.h>
#include <xen/events.h>

#include <xen/hvc-console.h>
#include "xen-ops.h"
#include "mmu.h"

cpumask_var_t xen_cpu_initialized_map;

static DEFINE_PER_CPU(int, xen_resched_irq);
static DEFINE_PER_CPU(int, xen_callfunc_irq);
static DEFINE_PER_CPU(int, xen_callfuncsingle_irq);
static DEFINE_PER_CPU(int, xen_irq_work);
static DEFINE_PER_CPU(int, xen_debug_irq) = -1;

static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id);
static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id);
static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);

/*
 * Reschedule call back.
 */
static irqreturn_t xen_reschedule_interrupt(int irq, void *dev_id)
{
    inc_irq_stat(irq_resched_count);
    scheduler_ipi();

    return IRQ_HANDLED;
}

static void __cpuinit cpu_bringup(void)
{
    int cpu;

    cpu_init();
    touch_softlockup_watchdog();
    preempt_disable();

    xen_enable_sysenter();
    xen_enable_syscall();

    cpu = smp_processor_id();
    smp_store_cpu_info(cpu);
    cpu_data(cpu).x86_max_cores = 1;
    set_cpu_sibling_map(cpu);

    xen_setup_cpu_clockevents();

    notify_cpu_starting(cpu);

    set_cpu_online(cpu, true);

    this_cpu_write(cpu_state, CPU_ONLINE);

    wmb();

    /* We can take interrupts now: we're officially "up". */
    local_irq_enable();

    wmb();          /* make sure everything is out */
}

static void __cpuinit cpu_bringup_and_idle(void)
{
    cpu_bringup();
    cpu_idle();
}

static int xen_smp_intr_init(unsigned int cpu)
{
    int rc;
    const char *resched_name, *callfunc_name, *debug_name;

    resched_name = kasprintf(GFP_KERNEL, "resched%d", cpu);
    rc = bind_ipi_to_irqhandler(XEN_RESCHEDULE_VECTOR,
                    cpu,
                    xen_reschedule_interrupt,
                    IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
                    resched_name,
                    NULL);
    if (rc < 0)
        goto fail;
    per_cpu(xen_resched_irq, cpu) = rc;

    callfunc_name = kasprintf(GFP_KERNEL, "callfunc%d", cpu);
    rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_VECTOR,
                    cpu,
                    xen_call_function_interrupt,
                    IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
                    callfunc_name,
                    NULL);
    if (rc < 0)
        goto fail;
    per_cpu(xen_callfunc_irq, cpu) = rc;

    debug_name = kasprintf(GFP_KERNEL, "debug%d", cpu);
    rc = bind_virq_to_irqhandler(VIRQ_DEBUG, cpu, xen_debug_interrupt,
                     IRQF_DISABLED | IRQF_PERCPU | IRQF_NOBALANCING,
                     debug_name, NULL);
    if (rc < 0)
        goto fail;
    per_cpu(xen_debug_irq, cpu) = rc;

    callfunc_name = kasprintf(GFP_KERNEL, "callfuncsingle%d", cpu);
    rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_SINGLE_VECTOR,
                    cpu,
                    xen_call_function_single_interrupt,
                    IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
                    callfunc_name,
                    NULL);
    if (rc < 0)
        goto fail;
    per_cpu(xen_callfuncsingle_irq, cpu) = rc;

    callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
    rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
                    cpu,
                    xen_irq_work_interrupt,
                    IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
                    callfunc_name,
                    NULL);
    if (rc < 0)
        goto fail;
    per_cpu(xen_irq_work, cpu) = rc;

    return 0;

 fail:
    if (per_cpu(xen_resched_irq, cpu) >= 0)
        unbind_from_irqhandler(per_cpu(xen_resched_irq, cpu), NULL);
    if (per_cpu(xen_callfunc_irq, cpu) >= 0)
        unbind_from_irqhandler(per_cpu(xen_callfunc_irq, cpu), NULL);
    if (per_cpu(xen_debug_irq, cpu) >= 0)
        unbind_from_irqhandler(per_cpu(xen_debug_irq, cpu), NULL);
    if (per_cpu(xen_callfuncsingle_irq, cpu) >= 0)
        unbind_from_irqhandler(per_cpu(xen_callfuncsingle_irq, cpu),
                       NULL);
    if (per_cpu(xen_irq_work, cpu) >= 0)
        unbind_from_irqhandler(per_cpu(xen_irq_work, cpu), NULL);

    return rc;
}

static void __init xen_fill_possible_map(void)
{
    int i, rc;

    if (xen_initial_domain())
        return;

    for (i = 0; i < nr_cpu_ids; i++) {
        rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
        if (rc >= 0) {
            num_processors++;
            set_cpu_possible(i, true);
        }
    }
}

static void __init xen_filter_cpu_maps(void)
{
    int i, rc;
    unsigned int subtract = 0;

    if (!xen_initial_domain())
        return;

    num_processors = 0;
    disabled_cpus = 0;
    for (i = 0; i < nr_cpu_ids; i++) {
        rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
        if (rc >= 0) {
            num_processors++;
            set_cpu_possible(i, true);
        } else {
            set_cpu_possible(i, false);
            set_cpu_present(i, false);
            subtract++;
        }
    }
#ifdef CONFIG_HOTPLUG_CPU
    /* This is akin to using 'nr_cpus' on the Linux command line.
     * Which is OK as when we use 'dom0_max_vcpus=X' we can only
     * have up to X, while nr_cpu_ids is greater than X. This
     * normally is not a problem, except when CPU hotplugging
     * is involved and then there might be more than X CPUs
     * in the guest - which will not work as there is no
     * hypercall to expand the max number of VCPUs an already
     * running guest has. So cap it up to X. */
    if (subtract)
        nr_cpu_ids = nr_cpu_ids - subtract;
#endif

}

static void __init xen_smp_prepare_boot_cpu(void)
{
    BUG_ON(smp_processor_id() != 0);
    native_smp_prepare_boot_cpu();

    /* We've switched to the "real" per-cpu gdt, so make sure the
       old memory can be recycled */
    make_lowmem_page_readwrite(xen_initial_gdt);

    xen_filter_cpu_maps();
    xen_setup_vcpu_info_placement();
}

static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
{
    unsigned cpu;
    unsigned int i;

    if (skip_ioapic_setup) {
        char *m = (max_cpus == 0) ?
            "The nosmp parameter is incompatible with Xen; " \
            "use Xen dom0_max_vcpus=1 parameter" :
            "The noapic parameter is incompatible with Xen";

        xen_raw_printk(m);
        panic(m);
    }
    xen_init_lock_cpu(0);

    smp_store_cpu_info(0);
    cpu_data(0).x86_max_cores = 1;

    for_each_possible_cpu(i) {
        zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
        zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
        zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
    }
    set_cpu_sibling_map(0);

    if (xen_smp_intr_init(0))
        BUG();

    if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
        panic("could not allocate xen_cpu_initialized_map\n");

    cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));

    /* Restrict the possible_map according to max_cpus. */
    while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
        for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
            continue;
        set_cpu_possible(cpu, false);
    }

    for_each_possible_cpu(cpu)
        set_cpu_present(cpu, true);
}

static int __cpuinit
cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
{
    struct vcpu_guest_context *ctxt;
    struct desc_struct *gdt;
    unsigned long gdt_mfn;

    if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
        return 0;

    ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
    if (ctxt == NULL)
        return -ENOMEM;

    gdt = get_cpu_gdt_table(cpu);

    ctxt->flags = VGCF_IN_KERNEL;
    ctxt->user_regs.ds = __USER_DS;
    ctxt->user_regs.es = __USER_DS;
    ctxt->user_regs.ss = __KERNEL_DS;
#ifdef CONFIG_X86_32
    ctxt->user_regs.fs = __KERNEL_PERCPU;
    ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
#else
    ctxt->gs_base_kernel = per_cpu_offset(cpu);
#endif
    ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
    ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */

    memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));

    xen_copy_trap_info(ctxt->trap_ctxt);

    ctxt->ldt_ents = 0;

    BUG_ON((unsigned long)gdt & ~PAGE_MASK);

    gdt_mfn = arbitrary_virt_to_mfn(gdt);
    make_lowmem_page_readonly(gdt);
    make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));

    ctxt->gdt_frames[0] = gdt_mfn;
    ctxt->gdt_ents      = GDT_ENTRIES;

    ctxt->user_regs.cs = __KERNEL_CS;
    ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);

    ctxt->kernel_ss = __KERNEL_DS;
    ctxt->kernel_sp = idle->thread.sp0;

#ifdef CONFIG_X86_32
    ctxt->event_callback_cs     = __KERNEL_CS;
    ctxt->failsafe_callback_cs  = __KERNEL_CS;
#endif
    ctxt->event_callback_eip    = (unsigned long)xen_hypervisor_callback;
    ctxt->failsafe_callback_eip = (unsigned long)xen_failsafe_callback;

    per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
    ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));

    if (HYPERVISOR_vcpu_op(VCPUOP_initialise, cpu, ctxt))
        BUG();

    kfree(ctxt);
    return 0;
}

static int __cpuinit xen_cpu_up(unsigned int cpu, struct task_struct *idle)
{
    int rc;

    per_cpu(current_task, cpu) = idle;
#ifdef CONFIG_X86_32
    irq_ctx_init(cpu);
#else
    clear_tsk_thread_flag(idle, TIF_FORK);
    per_cpu(kernel_stack, cpu) =
        (unsigned long)task_stack_page(idle) -
        KERNEL_STACK_OFFSET + THREAD_SIZE;
#endif
    xen_setup_runstate_info(cpu);
    xen_setup_timer(cpu);
    xen_init_lock_cpu(cpu);

    per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;

    /* make sure interrupts start blocked */
    per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;

    rc = cpu_initialize_context(cpu, idle);
    if (rc)
        return rc;

    if (num_online_cpus() == 1)
        /* Just in case we booted with a single CPU. */
        alternatives_enable_smp();

    rc = xen_smp_intr_init(cpu);
    if (rc)
        return rc;

    rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
    BUG_ON(rc);

    while(per_cpu(cpu_state, cpu) != CPU_ONLINE) {
        HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
        barrier();
    }

    return 0;
}

static void xen_smp_cpus_done(unsigned int max_cpus)
{
}

#ifdef CONFIG_HOTPLUG_CPU
static int xen_cpu_disable(void)
{
    unsigned int cpu = smp_processor_id();
    if (cpu == 0)
        return -EBUSY;

    cpu_disable_common();

    load_cr3(swapper_pg_dir);
    return 0;
}

static void xen_cpu_die(unsigned int cpu)
{
    while (HYPERVISOR_vcpu_op(VCPUOP_is_up, cpu, NULL)) {
        current->state = TASK_UNINTERRUPTIBLE;
        schedule_timeout(HZ/10);
    }
    unbind_from_irqhandler(per_cpu(xen_resched_irq, cpu), NULL);
    unbind_from_irqhandler(per_cpu(xen_callfunc_irq, cpu), NULL);
    unbind_from_irqhandler(per_cpu(xen_debug_irq, cpu), NULL);
    unbind_from_irqhandler(per_cpu(xen_callfuncsingle_irq, cpu), NULL);
    unbind_from_irqhandler(per_cpu(xen_irq_work, cpu), NULL);
    xen_uninit_lock_cpu(cpu);
    xen_teardown_timer(cpu);
}

static void __cpuinit xen_play_dead(void) /* used only with HOTPLUG_CPU */
{
    play_dead_common();
    HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
    cpu_bringup();
    /*
     * Balance out the preempt calls - as we are running in cpu_idle
     * loop which has been called at bootup from cpu_bringup_and_idle.
     * The cpucpu_bringup_and_idle called cpu_bringup which made a
     * preempt_disable() So this preempt_enable will balance it out.
     */
    preempt_enable();
}

#else /* !CONFIG_HOTPLUG_CPU */
static int xen_cpu_disable(void)
{
    return -ENOSYS;
}

static void xen_cpu_die(unsigned int cpu)
{
    BUG();
}

static void xen_play_dead(void)
{
    BUG();
}

#endif
static void stop_self(void *v)
{
    int cpu = smp_processor_id();

    /* make sure we're not pinning something down */
    load_cr3(swapper_pg_dir);
    /* should set up a minimal gdt */

    set_cpu_online(cpu, false);

    HYPERVISOR_vcpu_op(VCPUOP_down, cpu, NULL);
    BUG();
}

static void xen_stop_other_cpus(int wait)
{
    smp_call_function(stop_self, NULL, wait);
}

static void xen_smp_send_reschedule(int cpu)
{
    xen_send_IPI_one(cpu, XEN_RESCHEDULE_VECTOR);
}

static void __xen_send_IPI_mask(const struct cpumask *mask,
                  int vector)
{
    unsigned cpu;

    for_each_cpu_and(cpu, mask, cpu_online_mask)
        xen_send_IPI_one(cpu, vector);
}

static void xen_smp_send_call_function_ipi(const struct cpumask *mask)
{
    int cpu;

    __xen_send_IPI_mask(mask, XEN_CALL_FUNCTION_VECTOR);

    /* Make sure other vcpus get a chance to run if they need to. */
    for_each_cpu(cpu, mask) {
        if (xen_vcpu_stolen(cpu)) {
            HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
            break;
        }
    }
}

static void xen_smp_send_call_function_single_ipi(int cpu)
{
    __xen_send_IPI_mask(cpumask_of(cpu),
              XEN_CALL_FUNCTION_SINGLE_VECTOR);
}

static inline int xen_map_vector(int vector)
{
    int xen_vector;

    switch (vector) {
    case RESCHEDULE_VECTOR:
        xen_vector = XEN_RESCHEDULE_VECTOR;
        break;
    case CALL_FUNCTION_VECTOR:
        xen_vector = XEN_CALL_FUNCTION_VECTOR;
        break;
    case CALL_FUNCTION_SINGLE_VECTOR:
        xen_vector = XEN_CALL_FUNCTION_SINGLE_VECTOR;
        break;
    case IRQ_WORK_VECTOR:
        xen_vector = XEN_IRQ_WORK_VECTOR;
        break;
    default:
        xen_vector = -1;
        printk(KERN_ERR "xen: vector 0x%x is not implemented\n",
            vector);
    }

    return xen_vector;
}

void xen_send_IPI_mask(const struct cpumask *mask,
                  int vector)
{
    int xen_vector = xen_map_vector(vector);

    if (xen_vector >= 0)
        __xen_send_IPI_mask(mask, xen_vector);
}

void xen_send_IPI_all(int vector)
{
    int xen_vector = xen_map_vector(vector);

    if (xen_vector >= 0)
        __xen_send_IPI_mask(cpu_online_mask, xen_vector);
}

void xen_send_IPI_self(int vector)
{
    int xen_vector = xen_map_vector(vector);

    if (xen_vector >= 0)
        xen_send_IPI_one(smp_processor_id(), xen_vector);
}

void xen_send_IPI_mask_allbutself(const struct cpumask *mask,
                int vector)
{
    unsigned cpu;
    unsigned int this_cpu = smp_processor_id();

    if (!(num_online_cpus() > 1))
        return;

    for_each_cpu_and(cpu, mask, cpu_online_mask) {
        if (this_cpu == cpu)
            continue;

        xen_smp_send_call_function_single_ipi(cpu);
    }
}

void xen_send_IPI_allbutself(int vector)
{
    int xen_vector = xen_map_vector(vector);

    if (xen_vector >= 0)
        xen_send_IPI_mask_allbutself(cpu_online_mask, xen_vector);
}

static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id)
{
    irq_enter();
    generic_smp_call_function_interrupt();
    inc_irq_stat(irq_call_count);
    irq_exit();

    return IRQ_HANDLED;
}

static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id)
{
    irq_enter();
    generic_smp_call_function_single_interrupt();
    inc_irq_stat(irq_call_count);
    irq_exit();

    return IRQ_HANDLED;
}

static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
{
    irq_enter();
    irq_work_run();
    inc_irq_stat(apic_irq_work_irqs);
    irq_exit();

    return IRQ_HANDLED;
}

static const struct smp_ops xen_smp_ops __initconst = {
    .smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu,
    .smp_prepare_cpus = xen_smp_prepare_cpus,
    .smp_cpus_done = xen_smp_cpus_done,

    .cpu_up = xen_cpu_up,
    .cpu_die = xen_cpu_die,
    .cpu_disable = xen_cpu_disable,
    .play_dead = xen_play_dead,

    .stop_other_cpus = xen_stop_other_cpus,
    .smp_send_reschedule = xen_smp_send_reschedule,

    .send_call_func_ipi = xen_smp_send_call_function_ipi,
    .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
};

void __init xen_smp_init(void)
{
    smp_ops = xen_smp_ops;
    xen_fill_possible_map();
    xen_init_spinlocks();
}

static void __init xen_hvm_smp_prepare_cpus(unsigned int max_cpus)
{
    native_smp_prepare_cpus(max_cpus);
    WARN_ON(xen_smp_intr_init(0));

    xen_init_lock_cpu(0);
}

static int __cpuinit xen_hvm_cpu_up(unsigned int cpu, struct task_struct *tidle)
{
    int rc;
    rc = native_cpu_up(cpu, tidle);
    WARN_ON (xen_smp_intr_init(cpu));
    return rc;
}

static void xen_hvm_cpu_die(unsigned int cpu)
{
    unbind_from_irqhandler(per_cpu(xen_resched_irq, cpu), NULL);
    unbind_from_irqhandler(per_cpu(xen_callfunc_irq, cpu), NULL);
    unbind_from_irqhandler(per_cpu(xen_debug_irq, cpu), NULL);
    unbind_from_irqhandler(per_cpu(xen_callfuncsingle_irq, cpu), NULL);
    unbind_from_irqhandler(per_cpu(xen_irq_work, cpu), NULL);
    native_cpu_die(cpu);
}

void __init xen_hvm_smp_init(void)
{
    if (!xen_have_vector_callback)
        return;
    smp_ops.smp_prepare_cpus = xen_hvm_smp_prepare_cpus;
    smp_ops.smp_send_reschedule = xen_smp_send_reschedule;
    smp_ops.cpu_up = xen_hvm_cpu_up;
    smp_ops.cpu_die = xen_hvm_cpu_die;
    smp_ops.send_call_func_ipi = xen_smp_send_call_function_ipi;
    smp_ops.send_call_func_single_ipi = xen_smp_send_call_function_single_ipi;
}