kvm.c

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/*
 * KVM paravirt_ops implementation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * Copyright (C) 2007, Red Hat, Inc., Ingo Molnar <[email protected]>
 * Copyright IBM Corporation, 2007
 *   Authors: Anthony Liguori <[email protected]>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/kvm_para.h>
#include <linux/cpu.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/hardirq.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/hash.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/kprobes.h>
#include <asm/timer.h>
#include <asm/cpu.h>
#include <asm/traps.h>
#include <asm/desc.h>
#include <asm/tlbflush.h>
#include <asm/idle.h>
#include <asm/apic.h>
#include <asm/apicdef.h>
#include <asm/hypervisor.h>

static int kvmapf = 1;

static int parse_no_kvmapf(char *arg)
{
        kvmapf = 0;
        return 0;
}

early_param("no-kvmapf", parse_no_kvmapf);

static int steal_acc = 1;
static int parse_no_stealacc(char *arg)
{
        steal_acc = 0;
        return 0;
}

early_param("no-steal-acc", parse_no_stealacc);

static DEFINE_PER_CPU(struct kvm_vcpu_pv_apf_data, apf_reason) __aligned(64);
static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);
static int has_steal_clock = 0;

/*
 * No need for any "IO delay" on KVM
 */
static void kvm_io_delay(void)
{
}

#define KVM_TASK_SLEEP_HASHBITS 8
#define KVM_TASK_SLEEP_HASHSIZE (1<<KVM_TASK_SLEEP_HASHBITS)

struct kvm_task_sleep_node {
    struct hlist_node link;
    wait_queue_head_t wq;
    u32 token;
    int cpu;
    bool halted;
};

static struct kvm_task_sleep_head {
    spinlock_t lock;
    struct hlist_head list;
} async_pf_sleepers[KVM_TASK_SLEEP_HASHSIZE];

static struct kvm_task_sleep_node *_find_apf_task(struct kvm_task_sleep_head *b,
                          u32 token)
{
    struct hlist_node *p;

    hlist_for_each(p, &b->list) {
        struct kvm_task_sleep_node *n =
            hlist_entry(p, typeof(*n), link);
        if (n->token == token)
            return n;
    }

    return NULL;
}

void kvm_async_pf_task_wait(u32 token)
{
    u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
    struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
    struct kvm_task_sleep_node n, *e;
    DEFINE_WAIT(wait);
    int cpu, idle;

    cpu = get_cpu();
    idle = idle_cpu(cpu);
    put_cpu();

    spin_lock(&b->lock);
    e = _find_apf_task(b, token);
    if (e) {
        /* dummy entry exist -> wake up was delivered ahead of PF */
        hlist_del(&e->link);
        kfree(e);
        spin_unlock(&b->lock);
        return;
    }

    n.token = token;
    n.cpu = smp_processor_id();
    n.halted = idle || preempt_count() > 1;
    init_waitqueue_head(&n.wq);
    hlist_add_head(&n.link, &b->list);
    spin_unlock(&b->lock);

    for (;;) {
        if (!n.halted)
            prepare_to_wait(&n.wq, &wait, TASK_UNINTERRUPTIBLE);
        if (hlist_unhashed(&n.link))
            break;

        if (!n.halted) {
            local_irq_enable();
            schedule();
            local_irq_disable();
        } else {
            /*
             * We cannot reschedule. So halt.
             */
            native_safe_halt();
            local_irq_disable();
        }
    }
    if (!n.halted)
        finish_wait(&n.wq, &wait);

    return;
}
EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait);

static void apf_task_wake_one(struct kvm_task_sleep_node *n)
{
    hlist_del_init(&n->link);
    if (n->halted)
        smp_send_reschedule(n->cpu);
    else if (waitqueue_active(&n->wq))
        wake_up(&n->wq);
}

static void apf_task_wake_all(void)
{
    int i;

    for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) {
        struct hlist_node *p, *next;
        struct kvm_task_sleep_head *b = &async_pf_sleepers[i];
        spin_lock(&b->lock);
        hlist_for_each_safe(p, next, &b->list) {
            struct kvm_task_sleep_node *n =
                hlist_entry(p, typeof(*n), link);
            if (n->cpu == smp_processor_id())
                apf_task_wake_one(n);
        }
        spin_unlock(&b->lock);
    }
}

void kvm_async_pf_task_wake(u32 token)
{
    u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
    struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
    struct kvm_task_sleep_node *n;

    if (token == ~0) {
        apf_task_wake_all();
        return;
    }

again:
    spin_lock(&b->lock);
    n = _find_apf_task(b, token);
    if (!n) {
        /*
         * async PF was not yet handled.
         * Add dummy entry for the token.
         */
        n = kzalloc(sizeof(*n), GFP_ATOMIC);
        if (!n) {
            /*
             * Allocation failed! Busy wait while other cpu
             * handles async PF.
             */
            spin_unlock(&b->lock);
            cpu_relax();
            goto again;
        }
        n->token = token;
        n->cpu = smp_processor_id();
        init_waitqueue_head(&n->wq);
        hlist_add_head(&n->link, &b->list);
    } else
        apf_task_wake_one(n);
    spin_unlock(&b->lock);
    return;
}
EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake);

u32 kvm_read_and_reset_pf_reason(void)
{
    u32 reason = 0;

    if (__get_cpu_var(apf_reason).enabled) {
        reason = __get_cpu_var(apf_reason).reason;
        __get_cpu_var(apf_reason).reason = 0;
    }

    return reason;
}
EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason);

dotraplinkage void __kprobes
do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
{
    switch (kvm_read_and_reset_pf_reason()) {
    default:
        do_page_fault(regs, error_code);
        break;
    case KVM_PV_REASON_PAGE_NOT_PRESENT:
        /* page is swapped out by the host. */
        rcu_irq_enter();
        exit_idle();
        kvm_async_pf_task_wait((u32)read_cr2());
        rcu_irq_exit();
        break;
    case KVM_PV_REASON_PAGE_READY:
        rcu_irq_enter();
        exit_idle();
        kvm_async_pf_task_wake((u32)read_cr2());
        rcu_irq_exit();
        break;
    }
}

static void __init paravirt_ops_setup(void)
{
    pv_info.name = "KVM";
    pv_info.paravirt_enabled = 1;

    if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
        pv_cpu_ops.io_delay = kvm_io_delay;

#ifdef CONFIG_X86_IO_APIC
    no_timer_check = 1;
#endif
}

static void kvm_register_steal_time(void)
{
    int cpu = smp_processor_id();
    struct kvm_steal_time *st = &per_cpu(steal_time, cpu);

    if (!has_steal_clock)
        return;

    memset(st, 0, sizeof(*st));

    wrmsrl(MSR_KVM_STEAL_TIME, (__pa(st) | KVM_MSR_ENABLED));
    printk(KERN_INFO "kvm-stealtime: cpu %d, msr %lx\n",
        cpu, __pa(st));
}

static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;

static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
{
    if (__test_and_clear_bit(KVM_PV_EOI_BIT, &__get_cpu_var(kvm_apic_eoi)))
        return;
    apic_write(APIC_EOI, APIC_EOI_ACK);
}

void __cpuinit kvm_guest_cpu_init(void)
{
    if (!kvm_para_available())
        return;

    if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
        u64 pa = __pa(&__get_cpu_var(apf_reason));

#ifdef CONFIG_PREEMPT
        pa |= KVM_ASYNC_PF_SEND_ALWAYS;
#endif
        wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
        __get_cpu_var(apf_reason).enabled = 1;
        printk(KERN_INFO"KVM setup async PF for cpu %d\n",
               smp_processor_id());
    }

    if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) {
        unsigned long pa;
        /* Size alignment is implied but just to make it explicit. */
        BUILD_BUG_ON(__alignof__(kvm_apic_eoi) < 4);
        __get_cpu_var(kvm_apic_eoi) = 0;
        pa = __pa(&__get_cpu_var(kvm_apic_eoi)) | KVM_MSR_ENABLED;
        wrmsrl(MSR_KVM_PV_EOI_EN, pa);
    }

    if (has_steal_clock)
        kvm_register_steal_time();
}

static void kvm_pv_disable_apf(void)
{
    if (!__get_cpu_var(apf_reason).enabled)
        return;

    wrmsrl(MSR_KVM_ASYNC_PF_EN, 0);
    __get_cpu_var(apf_reason).enabled = 0;

    printk(KERN_INFO"Unregister pv shared memory for cpu %d\n",
           smp_processor_id());
}

static void kvm_pv_guest_cpu_reboot(void *unused)
{
    /*
     * We disable PV EOI before we load a new kernel by kexec,
     * since MSR_KVM_PV_EOI_EN stores a pointer into old kernel's memory.
     * New kernel can re-enable when it boots.
     */
    if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
        wrmsrl(MSR_KVM_PV_EOI_EN, 0);
    kvm_pv_disable_apf();
    kvm_disable_steal_time();
}

static int kvm_pv_reboot_notify(struct notifier_block *nb,
                unsigned long code, void *unused)
{
    if (code == SYS_RESTART)
        on_each_cpu(kvm_pv_guest_cpu_reboot, NULL, 1);
    return NOTIFY_DONE;
}

static struct notifier_block kvm_pv_reboot_nb = {
    .notifier_call = kvm_pv_reboot_notify,
};

static u64 kvm_steal_clock(int cpu)
{
    u64 steal;
    struct kvm_steal_time *src;
    int version;

    src = &per_cpu(steal_time, cpu);
    do {
        version = src->version;
        rmb();
        steal = src->steal;
        rmb();
    } while ((version & 1) || (version != src->version));

    return steal;
}

void kvm_disable_steal_time(void)
{
    if (!has_steal_clock)
        return;

    wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
}

#ifdef CONFIG_SMP
static void __init kvm_smp_prepare_boot_cpu(void)
{
    WARN_ON(kvm_register_clock("primary cpu clock"));
    kvm_guest_cpu_init();
    native_smp_prepare_boot_cpu();
}

static void __cpuinit kvm_guest_cpu_online(void *dummy)
{
    kvm_guest_cpu_init();
}

static void kvm_guest_cpu_offline(void *dummy)
{
    kvm_disable_steal_time();
    if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
        wrmsrl(MSR_KVM_PV_EOI_EN, 0);
    kvm_pv_disable_apf();
    apf_task_wake_all();
}

static int __cpuinit kvm_cpu_notify(struct notifier_block *self,
                    unsigned long action, void *hcpu)
{
    int cpu = (unsigned long)hcpu;
    switch (action) {
    case CPU_ONLINE:
    case CPU_DOWN_FAILED:
    case CPU_ONLINE_FROZEN:
        smp_call_function_single(cpu, kvm_guest_cpu_online, NULL, 0);
        break;
    case CPU_DOWN_PREPARE:
    case CPU_DOWN_PREPARE_FROZEN:
        smp_call_function_single(cpu, kvm_guest_cpu_offline, NULL, 1);
        break;
    default:
        break;
    }
    return NOTIFY_OK;
}

static struct notifier_block __cpuinitdata kvm_cpu_notifier = {
        .notifier_call  = kvm_cpu_notify,
};
#endif

static void __init kvm_apf_trap_init(void)
{
    set_intr_gate(14, &async_page_fault);
}

void __init kvm_guest_init(void)
{
    int i;

    if (!kvm_para_available())
        return;

    paravirt_ops_setup();
    register_reboot_notifier(&kvm_pv_reboot_nb);
    for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
        spin_lock_init(&async_pf_sleepers[i].lock);
    if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
        x86_init.irqs.trap_init = kvm_apf_trap_init;

    if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
        has_steal_clock = 1;
        pv_time_ops.steal_clock = kvm_steal_clock;
    }

    if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
        apic_set_eoi_write(kvm_guest_apic_eoi_write);

#ifdef CONFIG_SMP
    smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
    register_cpu_notifier(&kvm_cpu_notifier);
#else
    kvm_guest_cpu_init();
#endif
}

static bool __init kvm_detect(void)
{
    if (!kvm_para_available())
        return false;
    return true;
}

const struct hypervisor_x86 x86_hyper_kvm __refconst = {
    .name           = "KVM",
    .detect         = kvm_detect,
};
EXPORT_SYMBOL_GPL(x86_hyper_kvm);

static __init int activate_jump_labels(void)
{
    if (has_steal_clock) {
        static_key_slow_inc(&paravirt_steal_enabled);
        if (steal_acc)
            static_key_slow_inc(&paravirt_steal_rq_enabled);
    }

    return 0;
}
arch_initcall(activate_jump_labels);