/*
 * 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.
 *
 * This does not handle HOTPLUG_CPU yet.
 */
#include <linux/sched.h>
#include <linux/err.h>
#include <linux/smp.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/page.h>
#include <xen/events.h>

#include "xen-ops.h"
#include "mmu.h"

static cpumask_t cpu_initialized_map;
static DEFINE_PER_CPU(int, resched_irq);
static DEFINE_PER_CPU(int, callfunc_irq);

/*
 * Structure and data for smp_call_function(). This is designed to minimise
 * static memory requirements. It also looks cleaner.
 */
static DEFINE_SPINLOCK(call_lock);

struct call_data_struct {
        void (*func) (void *info);
        void *info;
        atomic_t started;
        atomic_t finished;
        int wait;
};

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

static struct call_data_struct *call_data;

/*
 * Reschedule call back. Nothing to do,
 * all the work is done automatically when
 * we return from the interrupt.
 */
static irqreturn_t xen_reschedule_interrupt(int irq, void *dev_id)
{
        return IRQ_HANDLED;
}

static __cpuinit void cpu_bringup_and_idle(void)
{
        int cpu = smp_processor_id();

        cpu_init();

        preempt_disable();
        per_cpu(cpu_state, cpu) = CPU_ONLINE;

        xen_setup_cpu_clockevents();

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

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

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

        per_cpu(resched_irq, cpu) = per_cpu(callfunc_irq, cpu) = -1;

        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(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(callfunc_irq, cpu) = rc;

        return 0;

 fail:
        if (per_cpu(resched_irq, cpu) >= 0)
                unbind_from_irqhandler(per_cpu(resched_irq, cpu), NULL);
        if (per_cpu(callfunc_irq, cpu) >= 0)
                unbind_from_irqhandler(per_cpu(callfunc_irq, cpu), NULL);
        return rc;
}

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

        for (i = 0; i < NR_CPUS; i++) {
                rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
                if (rc >= 0)
                        cpu_set(i, cpu_possible_map);
        }
}

void __init xen_smp_prepare_boot_cpu(void)
{
        int cpu;

        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(&per_cpu__gdt_page);

        for (cpu = 0; cpu < NR_CPUS; cpu++) {
                cpus_clear(per_cpu(cpu_sibling_map, cpu));
                /*
                 * cpu_core_map lives in a per cpu area that is cleared
                 * when the per cpu array is allocated.
                 *
                 * cpus_clear(per_cpu(cpu_core_map, cpu));
                 */
        }

        xen_setup_vcpu_info_placement();
}

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

        for (cpu = 0; cpu < NR_CPUS; cpu++) {
                cpus_clear(per_cpu(cpu_sibling_map, cpu));
                /*
                 * cpu_core_ map will be zeroed when the per
                 * cpu area is allocated.
                 *
                 * cpus_clear(per_cpu(cpu_core_map, cpu));
                 */
        }

        smp_store_cpu_info(0);
        set_cpu_sibling_map(0);

        if (xen_smp_intr_init(0))
                BUG();

        cpu_initialized_map = cpumask_of_cpu(0);

        /* Restrict the possible_map according to max_cpus. */
        while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
                for (cpu = NR_CPUS-1; !cpu_isset(cpu, cpu_possible_map); cpu--)
                        continue;
                cpu_clear(cpu, cpu_possible_map);
        }

        for_each_possible_cpu (cpu) {
                struct task_struct *idle;

                if (cpu == 0)
                        continue;

                idle = fork_idle(cpu);
                if (IS_ERR(idle))
                        panic("failed fork for CPU %d", cpu);

                cpu_set(cpu, cpu_present_map);
        }

        //init_xenbus_allowed_cpumask();
}

static __cpuinit int
cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
{
        struct vcpu_guest_context *ctxt;
        struct gdt_page *gdt = &per_cpu(gdt_page, cpu);

        if (cpu_test_and_set(cpu, cpu_initialized_map))
                return 0;

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

        ctxt->flags = VGCF_IN_KERNEL;
        ctxt->user_regs.ds = __USER_DS;
        ctxt->user_regs.es = __USER_DS;
        ctxt->user_regs.fs = __KERNEL_PERCPU;
        ctxt->user_regs.gs = 0;
        ctxt->user_regs.ss = __KERNEL_DS;
        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->gdt & ~PAGE_MASK);
        make_lowmem_page_readonly(gdt->gdt);

        ctxt->gdt_frames[0] = virt_to_mfn(gdt->gdt);
        ctxt->gdt_ents      = ARRAY_SIZE(gdt->gdt);

        ctxt->user_regs.cs = __KERNEL_CS;
        ctxt->user_regs.esp = idle->thread.esp0 - sizeof(struct pt_regs);

        ctxt->kernel_ss = __KERNEL_DS;
        ctxt->kernel_sp = idle->thread.esp0;

        ctxt->event_callback_cs     = __KERNEL_CS;
        ctxt->event_callback_eip    = (unsigned long)xen_hypervisor_callback;
        ctxt->failsafe_callback_cs  = __KERNEL_CS;
        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;
}

int __cpuinit xen_cpu_up(unsigned int cpu)
{
        struct task_struct *idle = idle_task(cpu);
        int rc;

#if 0
        rc = cpu_up_check(cpu);
        if (rc)
                return rc;
#endif

        init_gdt(cpu);
        per_cpu(current_task, cpu) = idle;
        irq_ctx_init(cpu);
        xen_setup_timer(cpu);

        /* 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)
                alternatives_smp_switch(1);

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

        smp_store_cpu_info(cpu);
        set_cpu_sibling_map(cpu);
        /* This must be done before setting cpu_online_map */
        wmb();

        cpu_set(cpu, cpu_online_map);

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

        return 0;
}

void xen_smp_cpus_done(unsigned int max_cpus)
{
}

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 */

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

void xen_smp_send_stop(void)
{
        smp_call_function(stop_self, NULL, 0, 0);
}

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


static void xen_send_IPI_mask(cpumask_t mask, enum ipi_vector vector)
{
        unsigned cpu;

        cpus_and(mask, mask, cpu_online_map);

        for_each_cpu_mask(cpu, mask)
                xen_send_IPI_one(cpu, vector);
}

static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id)
{
        void (*func) (void *info) = call_data->func;
        void *info = call_data->info;
        int wait = call_data->wait;

        /*
         * Notify initiating CPU that I've grabbed the data and am
         * about to execute the function
         */
        mb();
        atomic_inc(&call_data->started);
        /*
         * At this point the info structure may be out of scope unless wait==1
         */
        irq_enter();
        (*func)(info);
        __get_cpu_var(irq_stat).irq_call_count++;
        irq_exit();

        if (wait) {
                mb();           /* commit everything before setting finished */
                atomic_inc(&call_data->finished);
        }

        return IRQ_HANDLED;
}

int xen_smp_call_function_mask(cpumask_t mask, void (*func)(void *),
                               void *info, int wait)
{
        struct call_data_struct data;
        int cpus, cpu;
        bool yield;

        /* Holding any lock stops cpus from going down. */
        spin_lock(&call_lock);

        cpu_clear(smp_processor_id(), mask);

        cpus = cpus_weight(mask);
        if (!cpus) {
                spin_unlock(&call_lock);
                return 0;
        }

        /* Can deadlock when called with interrupts disabled */
        WARN_ON(irqs_disabled());

        data.func = func;
        data.info = info;
        atomic_set(&data.started, 0);
        data.wait = wait;
        if (wait)
                atomic_set(&data.finished, 0);

        call_data = &data;
        mb();                   /* write everything before IPI */

        /* Send a message to other CPUs and wait for them to respond */
        xen_send_IPI_mask(mask, XEN_CALL_FUNCTION_VECTOR);

        /* Make sure other vcpus get a chance to run if they need to. */
        yield = false;
        for_each_cpu_mask(cpu, mask)
                if (xen_vcpu_stolen(cpu))
                        yield = true;

        if (yield)
                HYPERVISOR_sched_op(SCHEDOP_yield, 0);

        /* Wait for response */
        while (atomic_read(&data.started) != cpus ||
               (wait && atomic_read(&data.finished) != cpus))
                cpu_relax();

        spin_unlock(&call_lock);

        return 0;
}