// SPDX-License-Identifier: GPL-2.0-only
/*
 * Kernel-based Virtual Machine driver for Linux
 *
 * This module enables machines with Intel VT-x extensions to run virtual
 * machines without emulation or binary translation.
 *
 * Copyright (C) 2006 Qumranet, Inc.
 * Copyright 2010 Red Hat, Inc. and/or its affiliates.
 *
 * Authors:
 *   Avi Kivity   <avi@qumranet.com>
 *   Yaniv Kamay  <yaniv@qumranet.com>
 */

#include <kvm/iodev.h>

#include <linux/kvm_host.h>
#include <linux/kvm.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/percpu.h>
#include <linux/mm.h>
#include <linux/miscdevice.h>
#include <linux/vmalloc.h>
#include <linux/reboot.h>
#include <linux/debugfs.h>
#include <linux/highmem.h>
#include <linux/file.h>
#include <linux/syscore_ops.h>
#include <linux/cpu.h>
#include <linux/sched/signal.h>
#include <linux/sched/mm.h>
#include <linux/sched/stat.h>
#include <linux/cpumask.h>
#include <linux/smp.h>
#include <linux/anon_inodes.h>
#include <linux/profile.h>
#include <linux/kvm_para.h>
#include <linux/pagemap.h>
#include <linux/mman.h>
#include <linux/swap.h>
#include <linux/bitops.h>
#include <linux/spinlock.h>
#include <linux/compat.h>
#include <linux/srcu.h>
#include <linux/hugetlb.h>
#include <linux/slab.h>
#include <linux/sort.h>
#include <linux/bsearch.h>
#include <linux/io.h>
#include <linux/lockdep.h>
#include <linux/kthread.h>

#include <asm/processor.h>
#include <asm/ioctl.h>
#include <linux/uaccess.h>

#include "coalesced_mmio.h"
#include "async_pf.h"
#include "vfio.h"

#define CREATE_TRACE_POINTS
#include <trace/events/kvm.h>

/* Worst case buffer size needed for holding an integer. */
#define ITOA_MAX_LEN 12

MODULE_AUTHOR("Qumranet");
MODULE_LICENSE("GPL");

/* Architectures should define their poll value according to the halt latency */
unsigned int halt_poll_ns = KVM_HALT_POLL_NS_DEFAULT;
module_param(halt_poll_ns, uint, 0644);
EXPORT_SYMBOL_GPL(halt_poll_ns);

/* Default doubles per-vcpu halt_poll_ns. */
unsigned int halt_poll_ns_grow = 2;
module_param(halt_poll_ns_grow, uint, 0644);
EXPORT_SYMBOL_GPL(halt_poll_ns_grow);

/* The start value to grow halt_poll_ns from */
unsigned int halt_poll_ns_grow_start = 10000; /* 10us */
module_param(halt_poll_ns_grow_start, uint, 0644);
EXPORT_SYMBOL_GPL(halt_poll_ns_grow_start);

/* Default resets per-vcpu halt_poll_ns . */
unsigned int halt_poll_ns_shrink;
module_param(halt_poll_ns_shrink, uint, 0644);
EXPORT_SYMBOL_GPL(halt_poll_ns_shrink);

/*
 * Ordering of locks:
 *
 *      kvm->lock --> kvm->slots_lock --> kvm->irq_lock
 */

DEFINE_MUTEX(kvm_lock);
static DEFINE_RAW_SPINLOCK(kvm_count_lock);
LIST_HEAD(vm_list);

static cpumask_var_t cpus_hardware_enabled;
static int kvm_usage_count;
static atomic_t hardware_enable_failed;

static struct kmem_cache *kvm_vcpu_cache;

static __read_mostly struct preempt_ops kvm_preempt_ops;
static DEFINE_PER_CPU(struct kvm_vcpu *, kvm_running_vcpu);

struct dentry *kvm_debugfs_dir;
EXPORT_SYMBOL_GPL(kvm_debugfs_dir);

static int kvm_debugfs_num_entries;
static const struct file_operations stat_fops_per_vm;

static long kvm_vcpu_ioctl(struct file *file, unsigned int ioctl,
                           unsigned long arg);
#ifdef CONFIG_KVM_COMPAT
static long kvm_vcpu_compat_ioctl(struct file *file, unsigned int ioctl,
                                  unsigned long arg);
#define KVM_COMPAT(c)   .compat_ioctl   = (c)
#else
/*
 * For architectures that don't implement a compat infrastructure,
 * adopt a double line of defense:
 * - Prevent a compat task from opening /dev/kvm
 * - If the open has been done by a 64bit task, and the KVM fd
 *   passed to a compat task, let the ioctls fail.
 */
static long kvm_no_compat_ioctl(struct file *file, unsigned int ioctl,
                                unsigned long arg) { return -EINVAL; }

static int kvm_no_compat_open(struct inode *inode, struct file *file)
{
        return is_compat_task() ? -ENODEV : 0;
}
#define KVM_COMPAT(c)   .compat_ioctl   = kvm_no_compat_ioctl,  \
                        .open           = kvm_no_compat_open
#endif
static int hardware_enable_all(void);
static void hardware_disable_all(void);

static void kvm_io_bus_destroy(struct kvm_io_bus *bus);

static void mark_page_dirty_in_slot(struct kvm_memory_slot *memslot, gfn_t gfn);

__visible bool kvm_rebooting;
EXPORT_SYMBOL_GPL(kvm_rebooting);

#define KVM_EVENT_CREATE_VM 0
#define KVM_EVENT_DESTROY_VM 1
static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm);
static unsigned long long kvm_createvm_count;
static unsigned long long kvm_active_vms;

__weak void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
                                                   unsigned long start, unsigned long end)
{
}

bool kvm_is_zone_device_pfn(kvm_pfn_t pfn)
{
        /*
         * The metadata used by is_zone_device_page() to determine whether or
         * not a page is ZONE_DEVICE is guaranteed to be valid if and only if
         * the device has been pinned, e.g. by get_user_pages().  WARN if the
         * page_count() is zero to help detect bad usage of this helper.
         */
        if (!pfn_valid(pfn) || WARN_ON_ONCE(!page_count(pfn_to_page(pfn))))
                return false;

        return is_zone_device_page(pfn_to_page(pfn));
}

bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
{
        /*
         * ZONE_DEVICE pages currently set PG_reserved, but from a refcounting
         * perspective they are "normal" pages, albeit with slightly different
         * usage rules.
         */
        if (pfn_valid(pfn))
                return PageReserved(pfn_to_page(pfn)) &&
                       !is_zero_pfn(pfn) &&
                       !kvm_is_zone_device_pfn(pfn);

        return true;
}

bool kvm_is_transparent_hugepage(kvm_pfn_t pfn)
{
        struct page *page = pfn_to_page(pfn);

        if (!PageTransCompoundMap(page))
                return false;

        return is_transparent_hugepage(compound_head(page));
}

/*
 * Switches to specified vcpu, until a matching vcpu_put()
 */
void vcpu_load(struct kvm_vcpu *vcpu)
{
        int cpu = get_cpu();

        __this_cpu_write(kvm_running_vcpu, vcpu);
        preempt_notifier_register(&vcpu->preempt_notifier);
        kvm_arch_vcpu_load(vcpu, cpu);
        put_cpu();
}
EXPORT_SYMBOL_GPL(vcpu_load);

void vcpu_put(struct kvm_vcpu *vcpu)
{
        preempt_disable();
        kvm_arch_vcpu_put(vcpu);
        preempt_notifier_unregister(&vcpu->preempt_notifier);
        __this_cpu_write(kvm_running_vcpu, NULL);
        preempt_enable();
}
EXPORT_SYMBOL_GPL(vcpu_put);

/* TODO: merge with kvm_arch_vcpu_should_kick */
static bool kvm_request_needs_ipi(struct kvm_vcpu *vcpu, unsigned req)
{
        int mode = kvm_vcpu_exiting_guest_mode(vcpu);

        /*
         * We need to wait for the VCPU to reenable interrupts and get out of
         * READING_SHADOW_PAGE_TABLES mode.
         */
        if (req & KVM_REQUEST_WAIT)
                return mode != OUTSIDE_GUEST_MODE;

        /*
         * Need to kick a running VCPU, but otherwise there is nothing to do.
         */
        return mode == IN_GUEST_MODE;
}

static void ack_flush(void *_completed)
{
}

static inline bool kvm_kick_many_cpus(const struct cpumask *cpus, bool wait)
{
        if (unlikely(!cpus))
                cpus = cpu_online_mask;

        if (cpumask_empty(cpus))
                return false;

        smp_call_function_many(cpus, ack_flush, NULL, wait);
        return true;
}

bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req,
                                 struct kvm_vcpu *except,
                                 unsigned long *vcpu_bitmap, cpumask_var_t tmp)
{
        int i, cpu, me;
        struct kvm_vcpu *vcpu;
        bool called;

        me = get_cpu();

        kvm_for_each_vcpu(i, vcpu, kvm) {
                if ((vcpu_bitmap && !test_bit(i, vcpu_bitmap)) ||
                    vcpu == except)
                        continue;

                kvm_make_request(req, vcpu);
                cpu = vcpu->cpu;

                if (!(req & KVM_REQUEST_NO_WAKEUP) && kvm_vcpu_wake_up(vcpu))
                        continue;

                if (tmp != NULL && cpu != -1 && cpu != me &&
                    kvm_request_needs_ipi(vcpu, req))
                        __cpumask_set_cpu(cpu, tmp);
        }

        called = kvm_kick_many_cpus(tmp, !!(req & KVM_REQUEST_WAIT));
        put_cpu();

        return called;
}

bool kvm_make_all_cpus_request_except(struct kvm *kvm, unsigned int req,
                                      struct kvm_vcpu *except)
{
        cpumask_var_t cpus;
        bool called;

        zalloc_cpumask_var(&cpus, GFP_ATOMIC);

        called = kvm_make_vcpus_request_mask(kvm, req, except, NULL, cpus);

        free_cpumask_var(cpus);
        return called;
}

bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
{
        return kvm_make_all_cpus_request_except(kvm, req, NULL);
}

#ifndef CONFIG_HAVE_KVM_ARCH_TLB_FLUSH_ALL
void kvm_flush_remote_tlbs(struct kvm *kvm)
{
        /*
         * Read tlbs_dirty before setting KVM_REQ_TLB_FLUSH in
         * kvm_make_all_cpus_request.
         */
        long dirty_count = smp_load_acquire(&kvm->tlbs_dirty);

        /*
         * We want to publish modifications to the page tables before reading
         * mode. Pairs with a memory barrier in arch-specific code.
         * - x86: smp_mb__after_srcu_read_unlock in vcpu_enter_guest
         * and smp_mb in walk_shadow_page_lockless_begin/end.
         * - powerpc: smp_mb in kvmppc_prepare_to_enter.
         *
         * There is already an smp_mb__after_atomic() before
         * kvm_make_all_cpus_request() reads vcpu->mode. We reuse that
         * barrier here.
         */
        if (!kvm_arch_flush_remote_tlb(kvm)
            || kvm_make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH))
                ++kvm->stat.remote_tlb_flush;
        cmpxchg(&kvm->tlbs_dirty, dirty_count, 0);
}
EXPORT_SYMBOL_GPL(kvm_flush_remote_tlbs);
#endif

void kvm_reload_remote_mmus(struct kvm *kvm)
{
        kvm_make_all_cpus_request(kvm, KVM_REQ_MMU_RELOAD);
}

#ifdef KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE
static inline void *mmu_memory_cache_alloc_obj(struct kvm_mmu_memory_cache *mc,
                                               gfp_t gfp_flags)
{
        gfp_flags |= mc->gfp_zero;

        if (mc->kmem_cache)
                return kmem_cache_alloc(mc->kmem_cache, gfp_flags);
        else
                return (void *)__get_free_page(gfp_flags);
}

int kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min)
{
        void *obj;

        if (mc->nobjs >= min)
                return 0;
        while (mc->nobjs < ARRAY_SIZE(mc->objects)) {
                obj = mmu_memory_cache_alloc_obj(mc, GFP_KERNEL_ACCOUNT);
                if (!obj)
                        return mc->nobjs >= min ? 0 : -ENOMEM;
                mc->objects[mc->nobjs++] = obj;
        }
        return 0;
}

int kvm_mmu_memory_cache_nr_free_objects(struct kvm_mmu_memory_cache *mc)
{
        return mc->nobjs;
}

void kvm_mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc)
{
        while (mc->nobjs) {
                if (mc->kmem_cache)
                        kmem_cache_free(mc->kmem_cache, mc->objects[--mc->nobjs]);
                else
                        free_page((unsigned long)mc->objects[--mc->nobjs]);
        }
}

void *kvm_mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc)
{
        void *p;

        if (WARN_ON(!mc->nobjs))
                p = mmu_memory_cache_alloc_obj(mc, GFP_ATOMIC | __GFP_ACCOUNT);
        else
                p = mc->objects[--mc->nobjs];
        BUG_ON(!p);
        return p;
}
#endif

static void kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id)
{
        mutex_init(&vcpu->mutex);
        vcpu->cpu = -1;
        vcpu->kvm = kvm;
        vcpu->vcpu_id = id;
        vcpu->pid = NULL;
        rcuwait_init(&vcpu->wait);
        kvm_async_pf_vcpu_init(vcpu);

        vcpu->pre_pcpu = -1;
        INIT_LIST_HEAD(&vcpu->blocked_vcpu_list);

        kvm_vcpu_set_in_spin_loop(vcpu, false);
        kvm_vcpu_set_dy_eligible(vcpu, false);
        vcpu->preempted = false;
        vcpu->ready = false;
        preempt_notifier_init(&vcpu->preempt_notifier, &kvm_preempt_ops);
}

void kvm_vcpu_destroy(struct kvm_vcpu *vcpu)
{
        kvm_arch_vcpu_destroy(vcpu);

        /*
         * No need for rcu_read_lock as VCPU_RUN is the only place that changes
         * the vcpu->pid pointer, and at destruction time all file descriptors
         * are already gone.
         */
        put_pid(rcu_dereference_protected(vcpu->pid, 1));

        free_page((unsigned long)vcpu->run);
        kmem_cache_free(kvm_vcpu_cache, vcpu);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_destroy);

#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
static inline struct kvm *mmu_notifier_to_kvm(struct mmu_notifier *mn)
{
        return container_of(mn, struct kvm, mmu_notifier);
}

static void kvm_mmu_notifier_invalidate_range(struct mmu_notifier *mn,
                                              struct mm_struct *mm,
                                              unsigned long start, unsigned long end)
{
        struct kvm *kvm = mmu_notifier_to_kvm(mn);
        int idx;

        idx = srcu_read_lock(&kvm->srcu);
        kvm_arch_mmu_notifier_invalidate_range(kvm, start, end);
        srcu_read_unlock(&kvm->srcu, idx);
}

static void kvm_mmu_notifier_change_pte(struct mmu_notifier *mn,
                                        struct mm_struct *mm,
                                        unsigned long address,
                                        pte_t pte)
{
        struct kvm *kvm = mmu_notifier_to_kvm(mn);
        int idx;

        idx = srcu_read_lock(&kvm->srcu);
        spin_lock(&kvm->mmu_lock);
        kvm->mmu_notifier_seq++;

        if (kvm_set_spte_hva(kvm, address, pte))
                kvm_flush_remote_tlbs(kvm);

        spin_unlock(&kvm->mmu_lock);
        srcu_read_unlock(&kvm->srcu, idx);
}

static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
                                        const struct mmu_notifier_range *range)
{
        struct kvm *kvm = mmu_notifier_to_kvm(mn);
        int need_tlb_flush = 0, idx;

        idx = srcu_read_lock(&kvm->srcu);
        spin_lock(&kvm->mmu_lock);
        /*
         * The count increase must become visible at unlock time as no
         * spte can be established without taking the mmu_lock and
         * count is also read inside the mmu_lock critical section.
         */
        kvm->mmu_notifier_count++;
        need_tlb_flush = kvm_unmap_hva_range(kvm, range->start, range->end,
                                             range->flags);
        need_tlb_flush |= kvm->tlbs_dirty;
        /* we've to flush the tlb before the pages can be freed */
        if (need_tlb_flush)
                kvm_flush_remote_tlbs(kvm);

        spin_unlock(&kvm->mmu_lock);
        srcu_read_unlock(&kvm->srcu, idx);

        return 0;
}

static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
                                        const struct mmu_notifier_range *range)
{
        struct kvm *kvm = mmu_notifier_to_kvm(mn);

        spin_lock(&kvm->mmu_lock);
        /*
         * This sequence increase will notify the kvm page fault that
         * the page that is going to be mapped in the spte could have
         * been freed.
         */
        kvm->mmu_notifier_seq++;
        smp_wmb();
        /*
         * The above sequence increase must be visible before the
         * below count decrease, which is ensured by the smp_wmb above
         * in conjunction with the smp_rmb in mmu_notifier_retry().
         */
        kvm->mmu_notifier_count--;
        spin_unlock(&kvm->mmu_lock);

        BUG_ON(kvm->mmu_notifier_count < 0);
}

static int kvm_mmu_notifier_clear_flush_young(struct mmu_notifier *mn,
                                              struct mm_struct *mm,
                                              unsigned long start,
                                              unsigned long end)
{
        struct kvm *kvm = mmu_notifier_to_kvm(mn);
        int young, idx;

        idx = srcu_read_lock(&kvm->srcu);
        spin_lock(&kvm->mmu_lock);

        young = kvm_age_hva(kvm, start, end);
        if (young)
                kvm_flush_remote_tlbs(kvm);

        spin_unlock(&kvm->mmu_lock);
        srcu_read_unlock(&kvm->srcu, idx);

        return young;
}

static int kvm_mmu_notifier_clear_young(struct mmu_notifier *mn,
                                        struct mm_struct *mm,
                                        unsigned long start,
                                        unsigned long end)
{
        struct kvm *kvm = mmu_notifier_to_kvm(mn);
        int young, idx;

        idx = srcu_read_lock(&kvm->srcu);
        spin_lock(&kvm->mmu_lock);
        /*
         * Even though we do not flush TLB, this will still adversely
         * affect performance on pre-Haswell Intel EPT, where there is
         * no EPT Access Bit to clear so that we have to tear down EPT
         * tables instead. If we find this unacceptable, we can always
         * add a parameter to kvm_age_hva so that it effectively doesn't
         * do anything on clear_young.
         *
         * Also note that currently we never issue secondary TLB flushes
         * from clear_young, leaving this job up to the regular system
         * cadence. If we find this inaccurate, we might come up with a
         * more sophisticated heuristic later.
         */
        young = kvm_age_hva(kvm, start, end);
        spin_unlock(&kvm->mmu_lock);
        srcu_read_unlock(&kvm->srcu, idx);

        return young;
}

static int kvm_mmu_notifier_test_young(struct mmu_notifier *mn,
                                       struct mm_struct *mm,
                                       unsigned long address)
{
        struct kvm *kvm = mmu_notifier_to_kvm(mn);
        int young, idx;

        idx = srcu_read_lock(&kvm->srcu);
        spin_lock(&kvm->mmu_lock);
        young = kvm_test_age_hva(kvm, address);
        spin_unlock(&kvm->mmu_lock);
        srcu_read_unlock(&kvm->srcu, idx);

        return young;
}

static void kvm_mmu_notifier_release(struct mmu_notifier *mn,
                                     struct mm_struct *mm)
{
        struct kvm *kvm = mmu_notifier_to_kvm(mn);
        int idx;

        idx = srcu_read_lock(&kvm->srcu);
        kvm_arch_flush_shadow_all(kvm);
        srcu_read_unlock(&kvm->srcu, idx);
}

static const struct mmu_notifier_ops kvm_mmu_notifier_ops = {
        .invalidate_range       = kvm_mmu_notifier_invalidate_range,
        .invalidate_range_start = kvm_mmu_notifier_invalidate_range_start,
        .invalidate_range_end   = kvm_mmu_notifier_invalidate_range_end,
        .clear_flush_young      = kvm_mmu_notifier_clear_flush_young,
        .clear_young            = kvm_mmu_notifier_clear_young,
        .test_young             = kvm_mmu_notifier_test_young,
        .change_pte             = kvm_mmu_notifier_change_pte,
        .release                = kvm_mmu_notifier_release,
};

static int kvm_init_mmu_notifier(struct kvm *kvm)
{
        kvm->mmu_notifier.ops = &kvm_mmu_notifier_ops;
        return mmu_notifier_register(&kvm->mmu_notifier, current->mm);
}

#else  /* !(CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER) */

static int kvm_init_mmu_notifier(struct kvm *kvm)
{
        return 0;
}

#endif /* CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER */

static struct kvm_memslots *kvm_alloc_memslots(void)
{
        int i;
        struct kvm_memslots *slots;

        slots = kvzalloc(sizeof(struct kvm_memslots), GFP_KERNEL_ACCOUNT);
        if (!slots)
                return NULL;

        for (i = 0; i < KVM_MEM_SLOTS_NUM; i++)
                slots->id_to_index[i] = -1;

        return slots;
}

static void kvm_destroy_dirty_bitmap(struct kvm_memory_slot *memslot)
{
        if (!memslot->dirty_bitmap)
                return;

        kvfree(memslot->dirty_bitmap);
        memslot->dirty_bitmap = NULL;
}

static void kvm_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
{
        kvm_destroy_dirty_bitmap(slot);

        kvm_arch_free_memslot(kvm, slot);

        slot->flags = 0;
        slot->npages = 0;
}

static void kvm_free_memslots(struct kvm *kvm, struct kvm_memslots *slots)
{
        struct kvm_memory_slot *memslot;

        if (!slots)
                return;

        kvm_for_each_memslot(memslot, slots)
                kvm_free_memslot(kvm, memslot);

        kvfree(slots);
}

static void kvm_destroy_vm_debugfs(struct kvm *kvm)
{
        int i;

        if (!kvm->debugfs_dentry)
                return;

        debugfs_remove_recursive(kvm->debugfs_dentry);

        if (kvm->debugfs_stat_data) {
                for (i = 0; i < kvm_debugfs_num_entries; i++)
                        kfree(kvm->debugfs_stat_data[i]);
                kfree(kvm->debugfs_stat_data);
        }
}

static int kvm_create_vm_debugfs(struct kvm *kvm, int fd)
{
        char dir_name[ITOA_MAX_LEN * 2];
        struct kvm_stat_data *stat_data;
        struct kvm_stats_debugfs_item *p;

        if (!debugfs_initialized())
                return 0;

        snprintf(dir_name, sizeof(dir_name), "%d-%d", task_pid_nr(current), fd);
        kvm->debugfs_dentry = debugfs_create_dir(dir_name, kvm_debugfs_dir);

        kvm->debugfs_stat_data = kcalloc(kvm_debugfs_num_entries,
                                         sizeof(*kvm->debugfs_stat_data),
                                         GFP_KERNEL_ACCOUNT);
        if (!kvm->debugfs_stat_data)
                return -ENOMEM;

        for (p = debugfs_entries; p->name; p++) {
                stat_data = kzalloc(sizeof(*stat_data), GFP_KERNEL_ACCOUNT);
                if (!stat_data)
                        return -ENOMEM;

                stat_data->kvm = kvm;
                stat_data->dbgfs_item = p;
                kvm->debugfs_stat_data[p - debugfs_entries] = stat_data;
                debugfs_create_file(p->name, KVM_DBGFS_GET_MODE(p),
                                    kvm->debugfs_dentry, stat_data,
                                    &stat_fops_per_vm);
        }
        return 0;
}

/*
 * Called after the VM is otherwise initialized, but just before adding it to
 * the vm_list.
 */
int __weak kvm_arch_post_init_vm(struct kvm *kvm)
{
        return 0;
}

/*
 * Called just after removing the VM from the vm_list, but before doing any
 * other destruction.
 */
void __weak kvm_arch_pre_destroy_vm(struct kvm *kvm)
{
}

static struct kvm *kvm_create_vm(unsigned long type)
{
        struct kvm *kvm = kvm_arch_alloc_vm();
        int r = -ENOMEM;
        int i;

        if (!kvm)
                return ERR_PTR(-ENOMEM);

        spin_lock_init(&kvm->mmu_lock);
        mmgrab(current->mm);
        kvm->mm = current->mm;
        kvm_eventfd_init(kvm);
        mutex_init(&kvm->lock);
        mutex_init(&kvm->irq_lock);
        mutex_init(&kvm->slots_lock);
        INIT_LIST_HEAD(&kvm->devices);

        BUILD_BUG_ON(KVM_MEM_SLOTS_NUM > SHRT_MAX);

        if (init_srcu_struct(&kvm->srcu))
                goto out_err_no_srcu;
        if (init_srcu_struct(&kvm->irq_srcu))
                goto out_err_no_irq_srcu;

        refcount_set(&kvm->users_count, 1);
        for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
                struct kvm_memslots *slots = kvm_alloc_memslots();

                if (!slots)
                        goto out_err_no_arch_destroy_vm;
                /* Generations must be different for each address space. */
                slots->generation = i;
                rcu_assign_pointer(kvm->memslots[i], slots);
        }

        for (i = 0; i < KVM_NR_BUSES; i++) {
                rcu_assign_pointer(kvm->buses[i],
                        kzalloc(sizeof(struct kvm_io_bus), GFP_KERNEL_ACCOUNT));
                if (!kvm->buses[i])
                        goto out_err_no_arch_destroy_vm;
        }

        kvm->max_halt_poll_ns = halt_poll_ns;

        r = kvm_arch_init_vm(kvm, type);
        if (r)
                goto out_err_no_arch_destroy_vm;

        r = hardware_enable_all();
        if (r)
                goto out_err_no_disable;

#ifdef CONFIG_HAVE_KVM_IRQFD
        INIT_HLIST_HEAD(&kvm->irq_ack_notifier_list);
#endif

        r = kvm_init_mmu_notifier(kvm);
        if (r)
                goto out_err_no_mmu_notifier;

        r = kvm_arch_post_init_vm(kvm);
        if (r)
                goto out_err;

        mutex_lock(&kvm_lock);
        list_add(&kvm->vm_list, &vm_list);
        mutex_unlock(&kvm_lock);

        preempt_notifier_inc();

        return kvm;

out_err:
#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
        if (kvm->mmu_notifier.ops)
                mmu_notifier_unregister(&kvm->mmu_notifier, current->mm);
#endif
out_err_no_mmu_notifier:
        hardware_disable_all();
out_err_no_disable:
        kvm_arch_destroy_vm(kvm);
out_err_no_arch_destroy_vm:
        WARN_ON_ONCE(!refcount_dec_and_test(&kvm->users_count));
        for (i = 0; i < KVM_NR_BUSES; i++)
                kfree(kvm_get_bus(kvm, i));
        for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
                kvm_free_memslots(kvm, __kvm_memslots(kvm, i));
        cleanup_srcu_struct(&kvm->irq_srcu);
out_err_no_irq_srcu:
        cleanup_srcu_struct(&kvm->srcu);
out_err_no_srcu:
        kvm_arch_free_vm(kvm);
        mmdrop(current->mm);
        return ERR_PTR(r);
}

static void kvm_destroy_devices(struct kvm *kvm)
{
        struct kvm_device *dev, *tmp;

        /*
         * We do not need to take the kvm->lock here, because nobody else
         * has a reference to the struct kvm at this point and therefore
         * cannot access the devices list anyhow.
         */
        list_for_each_entry_safe(dev, tmp, &kvm->devices, vm_node) {
                list_del(&dev->vm_node);
                dev->ops->destroy(dev);
        }
}

static void kvm_destroy_vm(struct kvm *kvm)
{
        int i;
        struct mm_struct *mm = kvm->mm;

        kvm_uevent_notify_change(KVM_EVENT_DESTROY_VM, kvm);
        kvm_destroy_vm_debugfs(kvm);
        kvm_arch_sync_events(kvm);
        mutex_lock(&kvm_lock);
        list_del(&kvm->vm_list);
        mutex_unlock(&kvm_lock);
        kvm_arch_pre_destroy_vm(kvm);

        kvm_free_irq_routing(kvm);
        for (i = 0; i < KVM_NR_BUSES; i++) {
                struct kvm_io_bus *bus = kvm_get_bus(kvm, i);

                if (bus)
                        kvm_io_bus_destroy(bus);
                kvm->buses[i] = NULL;
        }
        kvm_coalesced_mmio_free(kvm);
#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
        mmu_notifier_unregister(&kvm->mmu_notifier, kvm->mm);
#else
        kvm_arch_flush_shadow_all(kvm);
#endif
        kvm_arch_destroy_vm(kvm);
        kvm_destroy_devices(kvm);
        for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
                kvm_free_memslots(kvm, __kvm_memslots(kvm, i));
        cleanup_srcu_struct(&kvm->irq_srcu);
        cleanup_srcu_struct(&kvm->srcu);
        kvm_arch_free_vm(kvm);
        preempt_notifier_dec();
        hardware_disable_all();
        mmdrop(mm);
}

void kvm_get_kvm(struct kvm *kvm)
{
        refcount_inc(&kvm->users_count);
}
EXPORT_SYMBOL_GPL(kvm_get_kvm);

void kvm_put_kvm(struct kvm *kvm)
{
        if (refcount_dec_and_test(&kvm->users_count))
                kvm_destroy_vm(kvm);
}
EXPORT_SYMBOL_GPL(kvm_put_kvm);

/*
 * Used to put a reference that was taken on behalf of an object associated
 * with a user-visible file descriptor, e.g. a vcpu or device, if installation
 * of the new file descriptor fails and the reference cannot be transferred to
 * its final owner.  In such cases, the caller is still actively using @kvm and
 * will fail miserably if the refcount unexpectedly hits zero.
 */
void kvm_put_kvm_no_destroy(struct kvm *kvm)
{
        WARN_ON(refcount_dec_and_test(&kvm->users_count));
}
EXPORT_SYMBOL_GPL(kvm_put_kvm_no_destroy);

static int kvm_vm_release(struct inode *inode, struct file *filp)
{
        struct kvm *kvm = filp->private_data;

        kvm_irqfd_release(kvm);

        kvm_put_kvm(kvm);
        return 0;
}

/*
 * Allocation size is twice as large as the actual dirty bitmap size.
 * See kvm_vm_ioctl_get_dirty_log() why this is needed.
 */
static int kvm_alloc_dirty_bitmap(struct kvm_memory_slot *memslot)
{
        unsigned long dirty_bytes = 2 * kvm_dirty_bitmap_bytes(memslot);

        memslot->dirty_bitmap = kvzalloc(dirty_bytes, GFP_KERNEL_ACCOUNT);
        if (!memslot->dirty_bitmap)
                return -ENOMEM;

        return 0;
}

/*
 * Delete a memslot by decrementing the number of used slots and shifting all
 * other entries in the array forward one spot.
 */
static inline void kvm_memslot_delete(struct kvm_memslots *slots,
                                      struct kvm_memory_slot *memslot)
{
        struct kvm_memory_slot *mslots = slots->memslots;
        int i;

        if (WARN_ON(slots->id_to_index[memslot->id] == -1))
                return;

        slots->used_slots--;

        if (atomic_read(&slots->lru_slot) >= slots->used_slots)
                atomic_set(&slots->lru_slot, 0);

        for (i = slots->id_to_index[memslot->id]; i < slots->used_slots; i++) {
                mslots[i] = mslots[i + 1];
                slots->id_to_index[mslots[i].id] = i;
        }
        mslots[i] = *memslot;
        slots->id_to_index[memslot->id] = -1;
}

/*
 * "Insert" a new memslot by incrementing the number of used slots.  Returns
 * the new slot's initial index into the memslots array.
 */
static inline int kvm_memslot_insert_back(struct kvm_memslots *slots)
{
        return slots->used_slots++;
}

/*
 * Move a changed memslot backwards in the array by shifting existing slots
 * with a higher GFN toward the front of the array.  Note, the changed memslot
 * itself is not preserved in the array, i.e. not swapped at this time, only
 * its new index into the array is tracked.  Returns the changed memslot's
 * current index into the memslots array.
 */
static inline int kvm_memslot_move_backward(struct kvm_memslots *slots,
                                            struct kvm_memory_slot *memslot)
{
        struct kvm_memory_slot *mslots = slots->memslots;
        int i;

        if (WARN_ON_ONCE(slots->id_to_index[memslot->id] == -1) ||
            WARN_ON_ONCE(!slots->used_slots))
                return -1;

        /*
         * Move the target memslot backward in the array by shifting existing
         * memslots with a higher GFN (than the target memslot) towards the
         * front of the array.
         */
        for (i = slots->id_to_index[memslot->id]; i < slots->used_slots - 1; i++) {
                if (memslot->base_gfn > mslots[i + 1].base_gfn)
                        break;

                WARN_ON_ONCE(memslot->base_gfn == mslots[i + 1].base_gfn);

                /* Shift the next memslot forward one and update its index. */
                mslots[i] = mslots[i + 1];
                slots->id_to_index[mslots[i].id] = i;
        }
        return i;
}

/*
 * Move a changed memslot forwards in the array by shifting existing slots with
 * a lower GFN toward the back of the array.  Note, the changed memslot itself
 * is not preserved in the array, i.e. not swapped at this time, only its new
 * index into the array is tracked.  Returns the changed memslot's final index
 * into the memslots array.
 */
static inline int kvm_memslot_move_forward(struct kvm_memslots *slots,
                                           struct kvm_memory_slot *memslot,
                                           int start)
{
        struct kvm_memory_slot *mslots = slots->memslots;
        int i;

        for (i = start; i > 0; i--) {
                if (memslot->base_gfn < mslots[i - 1].base_gfn)
                        break;

                WARN_ON_ONCE(memslot->base_gfn == mslots[i - 1].base_gfn);

                /* Shift the next memslot back one and update its index. */
                mslots[i] = mslots[i - 1];
                slots->id_to_index[mslots[i].id] = i;
        }
        return i;
}

/*
 * Re-sort memslots based on their GFN to account for an added, deleted, or
 * moved memslot.  Sorting memslots by GFN allows using a binary search during
 * memslot lookup.
 *
 * IMPORTANT: Slots are sorted from highest GFN to lowest GFN!  I.e. the entry
 * at memslots[0] has the highest GFN.
 *
 * The sorting algorithm takes advantage of having initially sorted memslots
 * and knowing the position of the changed memslot.  Sorting is also optimized
 * by not swapping the updated memslot and instead only shifting other memslots
 * and tracking the new index for the update memslot.  Only once its final
 * index is known is the updated memslot copied into its position in the array.
 *
 *  - When deleting a memslot, the deleted memslot simply needs to be moved to
 *    the end of the array.
 *
 *  - When creating a memslot, the algorithm "inserts" the new memslot at the
 *    end of the array and then it forward to its correct location.
 *
 *  - When moving a memslot, the algorithm first moves the updated memslot
 *    backward to handle the scenario where the memslot's GFN was changed to a
 *    lower value.  update_memslots() then falls through and runs the same flow
 *    as creating a memslot to move the memslot forward to handle the scenario
 *    where its GFN was changed to a higher value.
 *
 * Note, slots are sorted from highest->lowest instead of lowest->highest for
 * historical reasons.  Originally, invalid memslots where denoted by having
 * GFN=0, thus sorting from highest->lowest naturally sorted invalid memslots
 * to the end of the array.  The current algorithm uses dedicated logic to
 * delete a memslot and thus does not rely on invalid memslots having GFN=0.
 *
 * The other historical motiviation for highest->lowest was to improve the
 * performance of memslot lookup.  KVM originally used a linear search starting
 * at memslots[0].  On x86, the largest memslot usually has one of the highest,
 * if not *the* highest, GFN, as the bulk of the guest's RAM is located in a
 * single memslot above the 4gb boundary.  As the largest memslot is also the
 * most likely to be referenced, sorting it to the front of the array was
 * advantageous.  The current binary search starts from the middle of the array
 * and uses an LRU pointer to improve performance for all memslots and GFNs.
 */
static void update_memslots(struct kvm_memslots *slots,
                            struct kvm_memory_slot *memslot,
                            enum kvm_mr_change change)
{
        int i;

        if (change == KVM_MR_DELETE) {
                kvm_memslot_delete(slots, memslot);
        } else {
                if (change == KVM_MR_CREATE)
                        i = kvm_memslot_insert_back(slots);
                else
                        i = kvm_memslot_move_backward(slots, memslot);
                i = kvm_memslot_move_forward(slots, memslot, i);

                /*
                 * Copy the memslot to its new position in memslots and update
                 * its index accordingly.
                 */
                slots->memslots[i] = *memslot;
                slots->id_to_index[memslot->id] = i;
        }
}

static int check_memory_region_flags(const struct kvm_userspace_memory_region *mem)
{
        u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;

#ifdef __KVM_HAVE_READONLY_MEM
        valid_flags |= KVM_MEM_READONLY;
#endif

        if (mem->flags & ~valid_flags)
                return -EINVAL;

        return 0;
}

static struct kvm_memslots *install_new_memslots(struct kvm *kvm,
                int as_id, struct kvm_memslots *slots)
{
        struct kvm_memslots *old_memslots = __kvm_memslots(kvm, as_id);
        u64 gen = old_memslots->generation;

        WARN_ON(gen & KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS);
        slots->generation = gen | KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS;

        rcu_assign_pointer(kvm->memslots[as_id], slots);
        synchronize_srcu_expedited(&kvm->srcu);

        /*
         * Increment the new memslot generation a second time, dropping the
         * update in-progress flag and incrementing the generation based on
         * the number of address spaces.  This provides a unique and easily
         * identifiable generation number while the memslots are in flux.
         */
        gen = slots->generation & ~KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS;

        /*
         * Generations must be unique even across address spaces.  We do not need
         * a global counter for that, instead the generation space is evenly split
         * across address spaces.  For example, with two address spaces, address
         * space 0 will use generations 0, 2, 4, ... while address space 1 will
         * use generations 1, 3, 5, ...
         */
        gen += KVM_ADDRESS_SPACE_NUM;

        kvm_arch_memslots_updated(kvm, gen);

        slots->generation = gen;

        return old_memslots;
}

/*
 * Note, at a minimum, the current number of used slots must be allocated, even
 * when deleting a memslot, as we need a complete duplicate of the memslots for
 * use when invalidating a memslot prior to deleting/moving the memslot.
 */
static struct kvm_memslots *kvm_dup_memslots(struct kvm_memslots *old,
                                             enum kvm_mr_change change)
{
        struct kvm_memslots *slots;
        size_t old_size, new_size;

        old_size = sizeof(struct kvm_memslots) +
                   (sizeof(struct kvm_memory_slot) * old->used_slots);

        if (change == KVM_MR_CREATE)
                new_size = old_size + sizeof(struct kvm_memory_slot);
        else
                new_size = old_size;

        slots = kvzalloc(new_size, GFP_KERNEL_ACCOUNT);
        if (likely(slots))
                memcpy(slots, old, old_size);

        return slots;
}

static int kvm_set_memslot(struct kvm *kvm,
                           const struct kvm_userspace_memory_region *mem,
                           struct kvm_memory_slot *old,
                           struct kvm_memory_slot *new, int as_id,
                           enum kvm_mr_change change)
{
        struct kvm_memory_slot *slot;
        struct kvm_memslots *slots;
        int r;

        slots = kvm_dup_memslots(__kvm_memslots(kvm, as_id), change);
        if (!slots)
                return -ENOMEM;

        if (change == KVM_MR_DELETE || change == KVM_MR_MOVE) {
                /*
                 * Note, the INVALID flag needs to be in the appropriate entry
                 * in the freshly allocated memslots, not in @old or @new.
                 */
                slot = id_to_memslot(slots, old->id);
                slot->flags |= KVM_MEMSLOT_INVALID;

                /*
                 * We can re-use the old memslots, the only difference from the
                 * newly installed memslots is the invalid flag, which will get
                 * dropped by update_memslots anyway.  We'll also revert to the
                 * old memslots if preparing the new memory region fails.
                 */
                slots = install_new_memslots(kvm, as_id, slots);

                /* From this point no new shadow pages pointing to a deleted,
                 * or moved, memslot will be created.
                 *
                 * validation of sp->gfn happens in:
                 *      - gfn_to_hva (kvm_read_guest, gfn_to_pfn)
                 *      - kvm_is_visible_gfn (mmu_check_root)
                 */
                kvm_arch_flush_shadow_memslot(kvm, slot);
        }

        r = kvm_arch_prepare_memory_region(kvm, new, mem, change);
        if (r)
                goto out_slots;

        update_memslots(slots, new, change);
        slots = install_new_memslots(kvm, as_id, slots);

        kvm_arch_commit_memory_region(kvm, mem, old, new, change);

        kvfree(slots);
        return 0;

out_slots:
        if (change == KVM_MR_DELETE || change == KVM_MR_MOVE)
                slots = install_new_memslots(kvm, as_id, slots);
        kvfree(slots);
        return r;
}

static int kvm_delete_memslot(struct kvm *kvm,
                              const struct kvm_userspace_memory_region *mem,
                              struct kvm_memory_slot *old, int as_id)
{
        struct kvm_memory_slot new;
        int r;

        if (!old->npages)
                return -EINVAL;

        memset(&new, 0, sizeof(new));
        new.id = old->id;

        r = kvm_set_memslot(kvm, mem, old, &new, as_id, KVM_MR_DELETE);
        if (r)
                return r;

        kvm_free_memslot(kvm, old);
        return 0;
}

/*
 * Allocate some memory and give it an address in the guest physical address
 * space.
 *
 * Discontiguous memory is allowed, mostly for framebuffers.
 *
 * Must be called holding kvm->slots_lock for write.
 */
int __kvm_set_memory_region(struct kvm *kvm,
                            const struct kvm_userspace_memory_region *mem)
{
        struct kvm_memory_slot old, new;
        struct kvm_memory_slot *tmp;
        enum kvm_mr_change change;
        int as_id, id;
        int r;

        r = check_memory_region_flags(mem);
        if (r)
                return r;

        as_id = mem->slot >> 16;
        id = (u16)mem->slot;

        /* General sanity checks */
        if (mem->memory_size & (PAGE_SIZE - 1))
                return -EINVAL;
        if (mem->guest_phys_addr & (PAGE_SIZE - 1))
                return -EINVAL;
        /* We can read the guest memory with __xxx_user() later on. */
        if ((mem->userspace_addr & (PAGE_SIZE - 1)) ||
             !access_ok((void __user *)(unsigned long)mem->userspace_addr,
                        mem->memory_size))
                return -EINVAL;
        if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_MEM_SLOTS_NUM)
                return -EINVAL;
        if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
                return -EINVAL;

        /*
         * Make a full copy of the old memslot, the pointer will become stale
         * when the memslots are re-sorted by update_memslots(), and the old
         * memslot needs to be referenced after calling update_memslots(), e.g.
         * to free its resources and for arch specific behavior.
         */
        tmp = id_to_memslot(__kvm_memslots(kvm, as_id), id);
        if (tmp) {
                old = *tmp;
                tmp = NULL;
        } else {
                memset(&old, 0, sizeof(old));
                old.id = id;
        }

        if (!mem->memory_size)
                return kvm_delete_memslot(kvm, mem, &old, as_id);

        new.id = id;
        new.base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
        new.npages = mem->memory_size >> PAGE_SHIFT;
        new.flags = mem->flags;
        new.userspace_addr = mem->userspace_addr;

        if (new.npages > KVM_MEM_MAX_NR_PAGES)
                return -EINVAL;

        if (!old.npages) {
                change = KVM_MR_CREATE;
                new.dirty_bitmap = NULL;
                memset(&new.arch, 0, sizeof(new.arch));
        } else { /* Modify an existing slot. */
                if ((new.userspace_addr != old.userspace_addr) ||
                    (new.npages != old.npages) ||
                    ((new.flags ^ old.flags) & KVM_MEM_READONLY))
                        return -EINVAL;

                if (new.base_gfn != old.base_gfn)
                        change = KVM_MR_MOVE;
                else if (new.flags != old.flags)
                        change = KVM_MR_FLAGS_ONLY;
                else /* Nothing to change. */
                        return 0;

                /* Copy dirty_bitmap and arch from the current memslot. */
                new.dirty_bitmap = old.dirty_bitmap;
                memcpy(&new.arch, &old.arch, sizeof(new.arch));
        }

        if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE)) {
                /* Check for overlaps */
                kvm_for_each_memslot(tmp, __kvm_memslots(kvm, as_id)) {
                        if (tmp->id == id)
                                continue;
                        if (!((new.base_gfn + new.npages <= tmp->base_gfn) ||
                              (new.base_gfn >= tmp->base_gfn + tmp->npages)))
                                return -EEXIST;
                }
        }

        /* Allocate/free page dirty bitmap as needed */
        if (!(new.flags & KVM_MEM_LOG_DIRTY_PAGES))
                new.dirty_bitmap = NULL;
        else if (!new.dirty_bitmap) {
                r = kvm_alloc_dirty_bitmap(&new);
                if (r)
                        return r;

                if (kvm_dirty_log_manual_protect_and_init_set(kvm))
                        bitmap_set(new.dirty_bitmap, 0, new.npages);
        }

        r = kvm_set_memslot(kvm, mem, &old, &new, as_id, change);
        if (r)
                goto out_bitmap;

        if (old.dirty_bitmap && !new.dirty_bitmap)
                kvm_destroy_dirty_bitmap(&old);
        return 0;

out_bitmap:
        if (new.dirty_bitmap && !old.dirty_bitmap)
                kvm_destroy_dirty_bitmap(&new);
        return r;
}
EXPORT_SYMBOL_GPL(__kvm_set_memory_region);

int kvm_set_memory_region(struct kvm *kvm,
                          const struct kvm_userspace_memory_region *mem)
{
        int r;

        mutex_lock(&kvm->slots_lock);
        r = __kvm_set_memory_region(kvm, mem);
        mutex_unlock(&kvm->slots_lock);
        return r;
}
EXPORT_SYMBOL_GPL(kvm_set_memory_region);

static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
                                          struct kvm_userspace_memory_region *mem)
{
        if ((u16)mem->slot >= KVM_USER_MEM_SLOTS)
                return -EINVAL;

        return kvm_set_memory_region(kvm, mem);
}

#ifndef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
/**
 * kvm_get_dirty_log - get a snapshot of dirty pages
 * @kvm:        pointer to kvm instance
 * @log:        slot id and address to which we copy the log
 * @is_dirty:   set to '1' if any dirty pages were found
 * @memslot:    set to the associated memslot, always valid on success
 */
int kvm_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log,
                      int *is_dirty, struct kvm_memory_slot **memslot)
{
        struct kvm_memslots *slots;
        int i, as_id, id;
        unsigned long n;
        unsigned long any = 0;

        *memslot = NULL;
        *is_dirty = 0;

        as_id = log->slot >> 16;
        id = (u16)log->slot;
        if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS)
                return -EINVAL;

        slots = __kvm_memslots(kvm, as_id);
        *memslot = id_to_memslot(slots, id);
        if (!(*memslot) || !(*memslot)->dirty_bitmap)
                return -ENOENT;

        kvm_arch_sync_dirty_log(kvm, *memslot);

        n = kvm_dirty_bitmap_bytes(*memslot);

        for (i = 0; !any && i < n/sizeof(long); ++i)
                any = (*memslot)->dirty_bitmap[i];

        if (copy_to_user(log->dirty_bitmap, (*memslot)->dirty_bitmap, n))
                return -EFAULT;

        if (any)
                *is_dirty = 1;
        return 0;
}
EXPORT_SYMBOL_GPL(kvm_get_dirty_log);

#else /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */
/**
 * kvm_get_dirty_log_protect - get a snapshot of dirty pages
 *      and reenable dirty page tracking for the corresponding pages.
 * @kvm:        pointer to kvm instance
 * @log:        slot id and address to which we copy the log
 *
 * We need to keep it in mind that VCPU threads can write to the bitmap
 * concurrently. So, to avoid losing track of dirty pages we keep the
 * following order:
 *
 *    1. Take a snapshot of the bit and clear it if needed.
 *    2. Write protect the corresponding page.
 *    3. Copy the snapshot to the userspace.
 *    4. Upon return caller flushes TLB's if needed.
 *
 * Between 2 and 4, the guest may write to the page using the remaining TLB
 * entry.  This is not a problem because the page is reported dirty using
 * the snapshot taken before and step 4 ensures that writes done after
 * exiting to userspace will be logged for the next call.
 *
 */
static int kvm_get_dirty_log_protect(struct kvm *kvm, struct kvm_dirty_log *log)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *memslot;
        int i, as_id, id;
        unsigned long n;
        unsigned long *dirty_bitmap;
        unsigned long *dirty_bitmap_buffer;
        bool flush;

        as_id = log->slot >> 16;
        id = (u16)log->slot;
        if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS)
                return -EINVAL;

        slots = __kvm_memslots(kvm, as_id);
        memslot = id_to_memslot(slots, id);
        if (!memslot || !memslot->dirty_bitmap)
                return -ENOENT;

        dirty_bitmap = memslot->dirty_bitmap;

        kvm_arch_sync_dirty_log(kvm, memslot);

        n = kvm_dirty_bitmap_bytes(memslot);
        flush = false;
        if (kvm->manual_dirty_log_protect) {
                /*
                 * Unlike kvm_get_dirty_log, we always return false in *flush,
                 * because no flush is needed until KVM_CLEAR_DIRTY_LOG.  There
                 * is some code duplication between this function and
                 * kvm_get_dirty_log, but hopefully all architecture
                 * transition to kvm_get_dirty_log_protect and kvm_get_dirty_log
                 * can be eliminated.
                 */
                dirty_bitmap_buffer = dirty_bitmap;
        } else {
                dirty_bitmap_buffer = kvm_second_dirty_bitmap(memslot);
                memset(dirty_bitmap_buffer, 0, n);

                spin_lock(&kvm->mmu_lock);
                for (i = 0; i < n / sizeof(long); i++) {
                        unsigned long mask;
                        gfn_t offset;

                        if (!dirty_bitmap[i])
                                continue;

                        flush = true;
                        mask = xchg(&dirty_bitmap[i], 0);
                        dirty_bitmap_buffer[i] = mask;

                        offset = i * BITS_PER_LONG;
                        kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot,
                                                                offset, mask);
                }
                spin_unlock(&kvm->mmu_lock);
        }

        if (flush)
                kvm_arch_flush_remote_tlbs_memslot(kvm, memslot);

        if (copy_to_user(log->dirty_bitmap, dirty_bitmap_buffer, n))
                return -EFAULT;
        return 0;
}


/**
 * kvm_vm_ioctl_get_dirty_log - get and clear the log of dirty pages in a slot
 * @kvm: kvm instance
 * @log: slot id and address to which we copy the log
 *
 * Steps 1-4 below provide general overview of dirty page logging. See
 * kvm_get_dirty_log_protect() function description for additional details.
 *
 * We call kvm_get_dirty_log_protect() to handle steps 1-3, upon return we
 * always flush the TLB (step 4) even if previous step failed  and the dirty
 * bitmap may be corrupt. Regardless of previous outcome the KVM logging API
 * does not preclude user space subsequent dirty log read. Flushing TLB ensures
 * writes will be marked dirty for next log read.
 *
 *   1. Take a snapshot of the bit and clear it if needed.
 *   2. Write protect the corresponding page.
 *   3. Copy the snapshot to the userspace.
 *   4. Flush TLB's if needed.
 */
static int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
                                      struct kvm_dirty_log *log)
{
        int r;

        mutex_lock(&kvm->slots_lock);

        r = kvm_get_dirty_log_protect(kvm, log);

        mutex_unlock(&kvm->slots_lock);
        return r;
}

/**
 * kvm_clear_dirty_log_protect - clear dirty bits in the bitmap
 *      and reenable dirty page tracking for the corresponding pages.
 * @kvm:        pointer to kvm instance
 * @log:        slot id and address from which to fetch the bitmap of dirty pages
 */
static int kvm_clear_dirty_log_protect(struct kvm *kvm,
                                       struct kvm_clear_dirty_log *log)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *memslot;
        int as_id, id;
        gfn_t offset;
        unsigned long i, n;
        unsigned long *dirty_bitmap;
        unsigned long *dirty_bitmap_buffer;
        bool flush;

        as_id = log->slot >> 16;
        id = (u16)log->slot;
        if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS)
                return -EINVAL;

        if (log->first_page & 63)
                return -EINVAL;

        slots = __kvm_memslots(kvm, as_id);
        memslot = id_to_memslot(slots, id);
        if (!memslot || !memslot->dirty_bitmap)
                return -ENOENT;

        dirty_bitmap = memslot->dirty_bitmap;

        n = ALIGN(log->num_pages, BITS_PER_LONG) / 8;

        if (log->first_page > memslot->npages ||
            log->num_pages > memslot->npages - log->first_page ||
            (log->num_pages < memslot->npages - log->first_page && (log->num_pages & 63)))
            return -EINVAL;

        kvm_arch_sync_dirty_log(kvm, memslot);

        flush = false;
        dirty_bitmap_buffer = kvm_second_dirty_bitmap(memslot);
        if (copy_from_user(dirty_bitmap_buffer, log->dirty_bitmap, n))
                return -EFAULT;

        spin_lock(&kvm->mmu_lock);
        for (offset = log->first_page, i = offset / BITS_PER_LONG,
                 n = DIV_ROUND_UP(log->num_pages, BITS_PER_LONG); n--;
             i++, offset += BITS_PER_LONG) {
                unsigned long mask = *dirty_bitmap_buffer++;
                atomic_long_t *p = (atomic_long_t *) &dirty_bitmap[i];
                if (!mask)
                        continue;

                mask &= atomic_long_fetch_andnot(mask, p);

                /*
                 * mask contains the bits that really have been cleared.  This
                 * never includes any bits beyond the length of the memslot (if
                 * the length is not aligned to 64 pages), therefore it is not
                 * a problem if userspace sets them in log->dirty_bitmap.
                */
                if (mask) {
                        flush = true;
                        kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot,
                                                                offset, mask);
                }
        }
        spin_unlock(&kvm->mmu_lock);

        if (flush)
                kvm_arch_flush_remote_tlbs_memslot(kvm, memslot);

        return 0;
}

static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
                                        struct kvm_clear_dirty_log *log)
{
        int r;

        mutex_lock(&kvm->slots_lock);

        r = kvm_clear_dirty_log_protect(kvm, log);

        mutex_unlock(&kvm->slots_lock);
        return r;
}
#endif /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */

struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
{
        return __gfn_to_memslot(kvm_memslots(kvm), gfn);
}
EXPORT_SYMBOL_GPL(gfn_to_memslot);

struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        return __gfn_to_memslot(kvm_vcpu_memslots(vcpu), gfn);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_memslot);

bool kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
{
        struct kvm_memory_slot *memslot = gfn_to_memslot(kvm, gfn);

        return kvm_is_visible_memslot(memslot);
}
EXPORT_SYMBOL_GPL(kvm_is_visible_gfn);

bool kvm_vcpu_is_visible_gfn(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        struct kvm_memory_slot *memslot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

        return kvm_is_visible_memslot(memslot);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_is_visible_gfn);

unsigned long kvm_host_page_size(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        struct vm_area_struct *vma;
        unsigned long addr, size;

        size = PAGE_SIZE;

        addr = kvm_vcpu_gfn_to_hva_prot(vcpu, gfn, NULL);
        if (kvm_is_error_hva(addr))
                return PAGE_SIZE;

        mmap_read_lock(current->mm);
        vma = find_vma(current->mm, addr);
        if (!vma)
                goto out;

        size = vma_kernel_pagesize(vma);

out:
        mmap_read_unlock(current->mm);

        return size;
}

static bool memslot_is_readonly(struct kvm_memory_slot *slot)
{
        return slot->flags & KVM_MEM_READONLY;
}

static unsigned long __gfn_to_hva_many(struct kvm_memory_slot *slot, gfn_t gfn,
                                       gfn_t *nr_pages, bool write)
{
        if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
                return KVM_HVA_ERR_BAD;

        if (memslot_is_readonly(slot) && write)
                return KVM_HVA_ERR_RO_BAD;

        if (nr_pages)
                *nr_pages = slot->npages - (gfn - slot->base_gfn);

        return __gfn_to_hva_memslot(slot, gfn);
}

static unsigned long gfn_to_hva_many(struct kvm_memory_slot *slot, gfn_t gfn,
                                     gfn_t *nr_pages)
{
        return __gfn_to_hva_many(slot, gfn, nr_pages, true);
}

unsigned long gfn_to_hva_memslot(struct kvm_memory_slot *slot,
                                        gfn_t gfn)
{
        return gfn_to_hva_many(slot, gfn, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_hva_memslot);

unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
{
        return gfn_to_hva_many(gfn_to_memslot(kvm, gfn), gfn, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_hva);

unsigned long kvm_vcpu_gfn_to_hva(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        return gfn_to_hva_many(kvm_vcpu_gfn_to_memslot(vcpu, gfn), gfn, NULL);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_hva);

/*
 * Return the hva of a @gfn and the R/W attribute if possible.
 *
 * @slot: the kvm_memory_slot which contains @gfn
 * @gfn: the gfn to be translated
 * @writable: used to return the read/write attribute of the @slot if the hva
 * is valid and @writable is not NULL
 */
unsigned long gfn_to_hva_memslot_prot(struct kvm_memory_slot *slot,
                                      gfn_t gfn, bool *writable)
{
        unsigned long hva = __gfn_to_hva_many(slot, gfn, NULL, false);

        if (!kvm_is_error_hva(hva) && writable)
                *writable = !memslot_is_readonly(slot);

        return hva;
}

unsigned long gfn_to_hva_prot(struct kvm *kvm, gfn_t gfn, bool *writable)
{
        struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);

        return gfn_to_hva_memslot_prot(slot, gfn, writable);
}

unsigned long kvm_vcpu_gfn_to_hva_prot(struct kvm_vcpu *vcpu, gfn_t gfn, bool *writable)
{
        struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

        return gfn_to_hva_memslot_prot(slot, gfn, writable);
}

static inline int check_user_page_hwpoison(unsigned long addr)
{
        int rc, flags = FOLL_HWPOISON | FOLL_WRITE;

        rc = get_user_pages(addr, 1, flags, NULL, NULL);
        return rc == -EHWPOISON;
}

/*
 * The fast path to get the writable pfn which will be stored in @pfn,
 * true indicates success, otherwise false is returned.  It's also the
 * only part that runs if we can in atomic context.
 */
static bool hva_to_pfn_fast(unsigned long addr, bool write_fault,
                            bool *writable, kvm_pfn_t *pfn)
{
        struct page *page[1];

        /*
         * Fast pin a writable pfn only if it is a write fault request
         * or the caller allows to map a writable pfn for a read fault
         * request.
         */
        if (!(write_fault || writable))
                return false;

        if (get_user_page_fast_only(addr, FOLL_WRITE, page)) {
                *pfn = page_to_pfn(page[0]);

                if (writable)
                        *writable = true;
                return true;
        }

        return false;
}

/*
 * The slow path to get the pfn of the specified host virtual address,
 * 1 indicates success, -errno is returned if error is detected.
 */
static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault,
                           bool *writable, kvm_pfn_t *pfn)
{
        unsigned int flags = FOLL_HWPOISON;
        struct page *page;
        int npages = 0;

        might_sleep();

        if (writable)
                *writable = write_fault;

        if (write_fault)
                flags |= FOLL_WRITE;
        if (async)
                flags |= FOLL_NOWAIT;

        npages = get_user_pages_unlocked(addr, 1, &page, flags);
        if (npages != 1)
                return npages;

        /* map read fault as writable if possible */
        if (unlikely(!write_fault) && writable) {
                struct page *wpage;

                if (get_user_page_fast_only(addr, FOLL_WRITE, &wpage)) {
                        *writable = true;
                        put_page(page);
                        page = wpage;
                }
        }
        *pfn = page_to_pfn(page);
        return npages;
}

static bool vma_is_valid(struct vm_area_struct *vma, bool write_fault)
{
        if (unlikely(!(vma->vm_flags & VM_READ)))
                return false;

        if (write_fault && (unlikely(!(vma->vm_flags & VM_WRITE))))
                return false;

        return true;
}

static int hva_to_pfn_remapped(struct vm_area_struct *vma,
                               unsigned long addr, bool *async,
                               bool write_fault, bool *writable,
                               kvm_pfn_t *p_pfn)
{
        unsigned long pfn;
        int r;

        r = follow_pfn(vma, addr, &pfn);
        if (r) {
                /*
                 * get_user_pages fails for VM_IO and VM_PFNMAP vmas and does
                 * not call the fault handler, so do it here.
                 */
                bool unlocked = false;
                r = fixup_user_fault(current->mm, addr,
                                     (write_fault ? FAULT_FLAG_WRITE : 0),
                                     &unlocked);
                if (unlocked)
                        return -EAGAIN;
                if (r)
                        return r;

                r = follow_pfn(vma, addr, &pfn);
                if (r)
                        return r;

        }

        if (writable)
                *writable = true;

        /*
         * Get a reference here because callers of *hva_to_pfn* and
         * *gfn_to_pfn* ultimately call kvm_release_pfn_clean on the
         * returned pfn.  This is only needed if the VMA has VM_MIXEDMAP
         * set, but the kvm_get_pfn/kvm_release_pfn_clean pair will
         * simply do nothing for reserved pfns.
         *
         * Whoever called remap_pfn_range is also going to call e.g.
         * unmap_mapping_range before the underlying pages are freed,
         * causing a call to our MMU notifier.
         */ 
        kvm_get_pfn(pfn);

        *p_pfn = pfn;
        return 0;
}

/*
 * Pin guest page in memory and return its pfn.
 * @addr: host virtual address which maps memory to the guest
 * @atomic: whether this function can sleep
 * @async: whether this function need to wait IO complete if the
 *         host page is not in the memory
 * @write_fault: whether we should get a writable host page
 * @writable: whether it allows to map a writable host page for !@write_fault
 *
 * The function will map a writable host page for these two cases:
 * 1): @write_fault = true
 * 2): @write_fault = false && @writable, @writable will tell the caller
 *     whether the mapping is writable.
 */
static kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
                        bool write_fault, bool *writable)
{
        struct vm_area_struct *vma;
        kvm_pfn_t pfn = 0;
        int npages, r;

        /* we can do it either atomically or asynchronously, not both */
        BUG_ON(atomic && async);

        if (hva_to_pfn_fast(addr, write_fault, writable, &pfn))
                return pfn;

        if (atomic)
                return KVM_PFN_ERR_FAULT;

        npages = hva_to_pfn_slow(addr, async, write_fault, writable, &pfn);
        if (npages == 1)
                return pfn;

        mmap_read_lock(current->mm);
        if (npages == -EHWPOISON ||
              (!async && check_user_page_hwpoison(addr))) {
                pfn = KVM_PFN_ERR_HWPOISON;
                goto exit;
        }

retry:
        vma = find_vma_intersection(current->mm, addr, addr + 1);

        if (vma == NULL)
                pfn = KVM_PFN_ERR_FAULT;
        else if (vma->vm_flags & (VM_IO | VM_PFNMAP)) {
                r = hva_to_pfn_remapped(vma, addr, async, write_fault, writable, &pfn);
                if (r == -EAGAIN)
                        goto retry;
                if (r < 0)
                        pfn = KVM_PFN_ERR_FAULT;
        } else {
                if (async && vma_is_valid(vma, write_fault))
                        *async = true;
                pfn = KVM_PFN_ERR_FAULT;
        }
exit:
        mmap_read_unlock(current->mm);
        return pfn;
}

kvm_pfn_t __gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn,
                               bool atomic, bool *async, bool write_fault,
                               bool *writable)
{
        unsigned long addr = __gfn_to_hva_many(slot, gfn, NULL, write_fault);

        if (addr == KVM_HVA_ERR_RO_BAD) {
                if (writable)

                        *writable = false;
                return KVM_PFN_ERR_RO_FAULT;
        }

        if (kvm_is_error_hva(addr)) {
                if (writable)
                        *writable = false;
                return KVM_PFN_NOSLOT;
        }

        /* Do not map writable pfn in the readonly memslot. */
        if (writable && memslot_is_readonly(slot)) {
                *writable = false;
                writable = NULL;
        }

        return hva_to_pfn(addr, atomic, async, write_fault,
                          writable);
}
EXPORT_SYMBOL_GPL(__gfn_to_pfn_memslot);

kvm_pfn_t gfn_to_pfn_prot(struct kvm *kvm, gfn_t gfn, bool write_fault,
                      bool *writable)
{
        return __gfn_to_pfn_memslot(gfn_to_memslot(kvm, gfn), gfn, false, NULL,
                                    write_fault, writable);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn_prot);

kvm_pfn_t gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn)
{
        return __gfn_to_pfn_memslot(slot, gfn, false, NULL, true, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn_memslot);

kvm_pfn_t gfn_to_pfn_memslot_atomic(struct kvm_memory_slot *slot, gfn_t gfn)
{
        return __gfn_to_pfn_memslot(slot, gfn, true, NULL, true, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn_memslot_atomic);

kvm_pfn_t kvm_vcpu_gfn_to_pfn_atomic(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        return gfn_to_pfn_memslot_atomic(kvm_vcpu_gfn_to_memslot(vcpu, gfn), gfn);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_pfn_atomic);

kvm_pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
{
        return gfn_to_pfn_memslot(gfn_to_memslot(kvm, gfn), gfn);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn);

kvm_pfn_t kvm_vcpu_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        return gfn_to_pfn_memslot(kvm_vcpu_gfn_to_memslot(vcpu, gfn), gfn);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_pfn);

int gfn_to_page_many_atomic(struct kvm_memory_slot *slot, gfn_t gfn,
                            struct page **pages, int nr_pages)
{
        unsigned long addr;
        gfn_t entry = 0;

        addr = gfn_to_hva_many(slot, gfn, &entry);
        if (kvm_is_error_hva(addr))
                return -1;

        if (entry < nr_pages)
                return 0;

        return get_user_pages_fast_only(addr, nr_pages, FOLL_WRITE, pages);
}
EXPORT_SYMBOL_GPL(gfn_to_page_many_atomic);

static struct page *kvm_pfn_to_page(kvm_pfn_t pfn)
{
        if (is_error_noslot_pfn(pfn))
                return KVM_ERR_PTR_BAD_PAGE;

        if (kvm_is_reserved_pfn(pfn)) {
                WARN_ON(1);
                return KVM_ERR_PTR_BAD_PAGE;
        }

        return pfn_to_page(pfn);
}

struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
{
        kvm_pfn_t pfn;

        pfn = gfn_to_pfn(kvm, gfn);

        return kvm_pfn_to_page(pfn);
}
EXPORT_SYMBOL_GPL(gfn_to_page);

void kvm_release_pfn(kvm_pfn_t pfn, bool dirty, struct gfn_to_pfn_cache *cache)
{
        if (pfn == 0)
                return;

        if (cache)
                cache->pfn = cache->gfn = 0;

        if (dirty)
                kvm_release_pfn_dirty(pfn);
        else
                kvm_release_pfn_clean(pfn);
}

static void kvm_cache_gfn_to_pfn(struct kvm_memory_slot *slot, gfn_t gfn,
                                 struct gfn_to_pfn_cache *cache, u64 gen)
{
        kvm_release_pfn(cache->pfn, cache->dirty, cache);

        cache->pfn = gfn_to_pfn_memslot(slot, gfn);
        cache->gfn = gfn;
        cache->dirty = false;
        cache->generation = gen;
}

static int __kvm_map_gfn(struct kvm_memslots *slots, gfn_t gfn,
                         struct kvm_host_map *map,
                         struct gfn_to_pfn_cache *cache,
                         bool atomic)
{
        kvm_pfn_t pfn;
        void *hva = NULL;
        struct page *page = KVM_UNMAPPED_PAGE;
        struct kvm_memory_slot *slot = __gfn_to_memslot(slots, gfn);
        u64 gen = slots->generation;

        if (!map)
                return -EINVAL;

        if (cache) {
                if (!cache->pfn || cache->gfn != gfn ||
                        cache->generation != gen) {
                        if (atomic)
                                return -EAGAIN;
                        kvm_cache_gfn_to_pfn(slot, gfn, cache, gen);
                }
                pfn = cache->pfn;
        } else {
                if (atomic)
                        return -EAGAIN;
                pfn = gfn_to_pfn_memslot(slot, gfn);
        }
        if (is_error_noslot_pfn(pfn))
                return -EINVAL;

        if (pfn_valid(pfn)) {
                page = pfn_to_page(pfn);
                if (atomic)
                        hva = kmap_atomic(page);
                else
                        hva = kmap(page);
#ifdef CONFIG_HAS_IOMEM
        } else if (!atomic) {
                hva = memremap(pfn_to_hpa(pfn), PAGE_SIZE, MEMREMAP_WB);
        } else {
                return -EINVAL;
#endif
        }

        if (!hva)
                return -EFAULT;

        map->page = page;
        map->hva = hva;
        map->pfn = pfn;
        map->gfn = gfn;

        return 0;
}

int kvm_map_gfn(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map,
                struct gfn_to_pfn_cache *cache, bool atomic)
{
        return __kvm_map_gfn(kvm_memslots(vcpu->kvm), gfn, map,
                        cache, atomic);
}
EXPORT_SYMBOL_GPL(kvm_map_gfn);

int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map)
{
        return __kvm_map_gfn(kvm_vcpu_memslots(vcpu), gfn, map,
                NULL, false);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_map);

static void __kvm_unmap_gfn(struct kvm_memory_slot *memslot,
                        struct kvm_host_map *map,
                        struct gfn_to_pfn_cache *cache,
                        bool dirty, bool atomic)
{
        if (!map)
                return;

        if (!map->hva)
                return;

        if (map->page != KVM_UNMAPPED_PAGE) {
                if (atomic)
                        kunmap_atomic(map->hva);
                else
                        kunmap(map->page);
        }
#ifdef CONFIG_HAS_IOMEM
        else if (!atomic)
                memunmap(map->hva);
        else
                WARN_ONCE(1, "Unexpected unmapping in atomic context");
#endif

        if (dirty)
                mark_page_dirty_in_slot(memslot, map->gfn);

        if (cache)
                cache->dirty |= dirty;
        else
                kvm_release_pfn(map->pfn, dirty, NULL);

        map->hva = NULL;
        map->page = NULL;
}

int kvm_unmap_gfn(struct kvm_vcpu *vcpu, struct kvm_host_map *map, 
                  struct gfn_to_pfn_cache *cache, bool dirty, bool atomic)
{
        __kvm_unmap_gfn(gfn_to_memslot(vcpu->kvm, map->gfn), map,
                        cache, dirty, atomic);
        return 0;
}
EXPORT_SYMBOL_GPL(kvm_unmap_gfn);

void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty)
{
        __kvm_unmap_gfn(kvm_vcpu_gfn_to_memslot(vcpu, map->gfn), map, NULL,
                        dirty, false);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_unmap);

struct page *kvm_vcpu_gfn_to_page(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        kvm_pfn_t pfn;

        pfn = kvm_vcpu_gfn_to_pfn(vcpu, gfn);

        return kvm_pfn_to_page(pfn);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_page);

void kvm_release_page_clean(struct page *page)
{
        WARN_ON(is_error_page(page));

        kvm_release_pfn_clean(page_to_pfn(page));
}
EXPORT_SYMBOL_GPL(kvm_release_page_clean);

void kvm_release_pfn_clean(kvm_pfn_t pfn)
{
        if (!is_error_noslot_pfn(pfn) && !kvm_is_reserved_pfn(pfn))
                put_page(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_release_pfn_clean);

void kvm_release_page_dirty(struct page *page)
{
        WARN_ON(is_error_page(page));

        kvm_release_pfn_dirty(page_to_pfn(page));
}
EXPORT_SYMBOL_GPL(kvm_release_page_dirty);

void kvm_release_pfn_dirty(kvm_pfn_t pfn)
{
        kvm_set_pfn_dirty(pfn);
        kvm_release_pfn_clean(pfn);
}
EXPORT_SYMBOL_GPL(kvm_release_pfn_dirty);

void kvm_set_pfn_dirty(kvm_pfn_t pfn)
{
        if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn))
                SetPageDirty(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_set_pfn_dirty);

void kvm_set_pfn_accessed(kvm_pfn_t pfn)
{
        if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn))
                mark_page_accessed(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_set_pfn_accessed);

void kvm_get_pfn(kvm_pfn_t pfn)
{
        if (!kvm_is_reserved_pfn(pfn))
                get_page(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_get_pfn);

static int next_segment(unsigned long len, int offset)
{
        if (len > PAGE_SIZE - offset)
                return PAGE_SIZE - offset;
        else
                return len;
}

static int __kvm_read_guest_page(struct kvm_memory_slot *slot, gfn_t gfn,
                                 void *data, int offset, int len)
{
        int r;
        unsigned long addr;

        addr = gfn_to_hva_memslot_prot(slot, gfn, NULL);
        if (kvm_is_error_hva(addr))
                return -EFAULT;
        r = __copy_from_user(data, (void __user *)addr + offset, len);
        if (r)
                return -EFAULT;
        return 0;
}

int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,
                        int len)
{
        struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);

        return __kvm_read_guest_page(slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_read_guest_page);

int kvm_vcpu_read_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn, void *data,
                             int offset, int len)
{
        struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

        return __kvm_read_guest_page(slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest_page);

int kvm_read_guest(struct kvm *kvm, gpa_t gpa, void *data, unsigned long len)
{
        gfn_t gfn = gpa >> PAGE_SHIFT;
        int seg;
        int offset = offset_in_page(gpa);
        int ret;

        while ((seg = next_segment(len, offset)) != 0) {
                ret = kvm_read_guest_page(kvm, gfn, data, offset, seg);
                if (ret < 0)
                        return ret;
                offset = 0;
                len -= seg;
                data += seg;
                ++gfn;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(kvm_read_guest);

int kvm_vcpu_read_guest(struct kvm_vcpu *vcpu, gpa_t gpa, void *data, unsigned long len)
{
        gfn_t gfn = gpa >> PAGE_SHIFT;
        int seg;
        int offset = offset_in_page(gpa);
        int ret;

        while ((seg = next_segment(len, offset)) != 0) {
                ret = kvm_vcpu_read_guest_page(vcpu, gfn, data, offset, seg);
                if (ret < 0)
                        return ret;
                offset = 0;
                len -= seg;
                data += seg;
                ++gfn;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest);

static int __kvm_read_guest_atomic(struct kvm_memory_slot *slot, gfn_t gfn,
                                   void *data, int offset, unsigned long len)
{
        int r;
        unsigned long addr;

        addr = gfn_to_hva_memslot_prot(slot, gfn, NULL);
        if (kvm_is_error_hva(addr))
                return -EFAULT;
        pagefault_disable();
        r = __copy_from_user_inatomic(data, (void __user *)addr + offset, len);
        pagefault_enable();
        if (r)
                return -EFAULT;
        return 0;
}

int kvm_vcpu_read_guest_atomic(struct kvm_vcpu *vcpu, gpa_t gpa,
                               void *data, unsigned long len)
{
        gfn_t gfn = gpa >> PAGE_SHIFT;
        struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
        int offset = offset_in_page(gpa);

        return __kvm_read_guest_atomic(slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest_atomic);

static int __kvm_write_guest_page(struct kvm_memory_slot *memslot, gfn_t gfn,
                                  const void *data, int offset, int len)
{
        int r;
        unsigned long addr;

        addr = gfn_to_hva_memslot(memslot, gfn);
        if (kvm_is_error_hva(addr))
                return -EFAULT;
        r = __copy_to_user((void __user *)addr + offset, data, len);
        if (r)
                return -EFAULT;
        mark_page_dirty_in_slot(memslot, gfn);
        return 0;
}

int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn,
                         const void *data, int offset, int len)
{
        struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);

        return __kvm_write_guest_page(slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_write_guest_page);

int kvm_vcpu_write_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn,
                              const void *data, int offset, int len)
{
        struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

        return __kvm_write_guest_page(slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_write_guest_page);

int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
                    unsigned long len)
{
        gfn_t gfn = gpa >> PAGE_SHIFT;
        int seg;
        int offset = offset_in_page(gpa);
        int ret;

        while ((seg = next_segment(len, offset)) != 0) {
                ret = kvm_write_guest_page(kvm, gfn, data, offset, seg);
                if (ret < 0)
                        return ret;
                offset = 0;
                len -= seg;
                data += seg;
                ++gfn;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(kvm_write_guest);

int kvm_vcpu_write_guest(struct kvm_vcpu *vcpu, gpa_t gpa, const void *data,
                         unsigned long len)
{
        gfn_t gfn = gpa >> PAGE_SHIFT;
        int seg;
        int offset = offset_in_page(gpa);
        int ret;

        while ((seg = next_segment(len, offset)) != 0) {
                ret = kvm_vcpu_write_guest_page(vcpu, gfn, data, offset, seg);
                if (ret < 0)
                        return ret;
                offset = 0;
                len -= seg;
                data += seg;
                ++gfn;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_write_guest);

static int __kvm_gfn_to_hva_cache_init(struct kvm_memslots *slots,
                                       struct gfn_to_hva_cache *ghc,
                                       gpa_t gpa, unsigned long len)
{
        int offset = offset_in_page(gpa);
        gfn_t start_gfn = gpa >> PAGE_SHIFT;
        gfn_t end_gfn = (gpa + len - 1) >> PAGE_SHIFT;
        gfn_t nr_pages_needed = end_gfn - start_gfn + 1;
        gfn_t nr_pages_avail;

        /* Update ghc->generation before performing any error checks. */
        ghc->generation = slots->generation;

        if (start_gfn > end_gfn) {
                ghc->hva = KVM_HVA_ERR_BAD;
                return -EINVAL;
        }

        /*
         * If the requested region crosses two memslots, we still
         * verify that the entire region is valid here.
         */
        for ( ; start_gfn <= end_gfn; start_gfn += nr_pages_avail) {
                ghc->memslot = __gfn_to_memslot(slots, start_gfn);
                ghc->hva = gfn_to_hva_many(ghc->memslot, start_gfn,
                                           &nr_pages_avail);
                if (kvm_is_error_hva(ghc->hva))
                        return -EFAULT;
        }

        /* Use the slow path for cross page reads and writes. */
        if (nr_pages_needed == 1)
                ghc->hva += offset;
        else
                ghc->memslot = NULL;

        ghc->gpa = gpa;
        ghc->len = len;
        return 0;
}

int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
                              gpa_t gpa, unsigned long len)
{
        struct kvm_memslots *slots = kvm_memslots(kvm);
        return __kvm_gfn_to_hva_cache_init(slots, ghc, gpa, len);
}
EXPORT_SYMBOL_GPL(kvm_gfn_to_hva_cache_init);

int kvm_write_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
                                  void *data, unsigned int offset,
                                  unsigned long len)
{
        struct kvm_memslots *slots = kvm_memslots(kvm);
        int r;
        gpa_t gpa = ghc->gpa + offset;

        BUG_ON(len + offset > ghc->len);

        if (slots->generation != ghc->generation) {
                if (__kvm_gfn_to_hva_cache_init(slots, ghc, ghc->gpa, ghc->len))
                        return -EFAULT;
        }

        if (kvm_is_error_hva(ghc->hva))
                return -EFAULT;

        if (unlikely(!ghc->memslot))
                return kvm_write_guest(kvm, gpa, data, len);

        r = __copy_to_user((void __user *)ghc->hva + offset, data, len);
        if (r)
                return -EFAULT;
        mark_page_dirty_in_slot(ghc->memslot, gpa >> PAGE_SHIFT);

        return 0;
}
EXPORT_SYMBOL_GPL(kvm_write_guest_offset_cached);

int kvm_write_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
                           void *data, unsigned long len)
{
        return kvm_write_guest_offset_cached(kvm, ghc, data, 0, len);
}
EXPORT_SYMBOL_GPL(kvm_write_guest_cached);

int kvm_read_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
                                 void *data, unsigned int offset,
                                 unsigned long len)
{
        struct kvm_memslots *slots = kvm_memslots(kvm);
        int r;
        gpa_t gpa = ghc->gpa + offset;

        BUG_ON(len + offset > ghc->len);

        if (slots->generation != ghc->generation) {
                if (__kvm_gfn_to_hva_cache_init(slots, ghc, ghc->gpa, ghc->len))
                        return -EFAULT;
        }

        if (kvm_is_error_hva(ghc->hva))
                return -EFAULT;

        if (unlikely(!ghc->memslot))
                return kvm_read_guest(kvm, gpa, data, len);

        r = __copy_from_user(data, (void __user *)ghc->hva + offset, len);
        if (r)
                return -EFAULT;

        return 0;
}
EXPORT_SYMBOL_GPL(kvm_read_guest_offset_cached);

int kvm_read_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
                          void *data, unsigned long len)
{
        return kvm_read_guest_offset_cached(kvm, ghc, data, 0, len);
}
EXPORT_SYMBOL_GPL(kvm_read_guest_cached);

int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len)
{
        const void *zero_page = (const void *) __va(page_to_phys(ZERO_PAGE(0)));

        return kvm_write_guest_page(kvm, gfn, zero_page, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_clear_guest_page);

int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len)
{
        gfn_t gfn = gpa >> PAGE_SHIFT;
        int seg;
        int offset = offset_in_page(gpa);
        int ret;

        while ((seg = next_segment(len, offset)) != 0) {
                ret = kvm_clear_guest_page(kvm, gfn, offset, seg);
                if (ret < 0)
                        return ret;
                offset = 0;
                len -= seg;
                ++gfn;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(kvm_clear_guest);

static void mark_page_dirty_in_slot(struct kvm_memory_slot *memslot,
                                    gfn_t gfn)
{
        if (memslot && memslot->dirty_bitmap) {
                unsigned long rel_gfn = gfn - memslot->base_gfn;

                set_bit_le(rel_gfn, memslot->dirty_bitmap);
        }
}

void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
{
        struct kvm_memory_slot *memslot;

        memslot = gfn_to_memslot(kvm, gfn);
        mark_page_dirty_in_slot(memslot, gfn);
}
EXPORT_SYMBOL_GPL(mark_page_dirty);

void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        struct kvm_memory_slot *memslot;

        memslot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
        mark_page_dirty_in_slot(memslot, gfn);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_mark_page_dirty);

void kvm_sigset_activate(struct kvm_vcpu *vcpu)
{
        if (!vcpu->sigset_active)
                return;

        /*
         * This does a lockless modification of ->real_blocked, which is fine
         * because, only current can change ->real_blocked and all readers of
         * ->real_blocked don't care as long ->real_blocked is always a subset
         * of ->blocked.
         */
        sigprocmask(SIG_SETMASK, &vcpu->sigset, &current->real_blocked);
}

void kvm_sigset_deactivate(struct kvm_vcpu *vcpu)
{
        if (!vcpu->sigset_active)
                return;

        sigprocmask(SIG_SETMASK, &current->real_blocked, NULL);
        sigemptyset(&current->real_blocked);
}

static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
{
        unsigned int old, val, grow, grow_start;

        old = val = vcpu->halt_poll_ns;
        grow_start = READ_ONCE(halt_poll_ns_grow_start);
        grow = READ_ONCE(halt_poll_ns_grow);
        if (!grow)
                goto out;

        val *= grow;
        if (val < grow_start)
                val = grow_start;

        if (val > halt_poll_ns)
                val = halt_poll_ns;

        vcpu->halt_poll_ns = val;
out:
        trace_kvm_halt_poll_ns_grow(vcpu->vcpu_id, val, old);
}

static void shrink_halt_poll_ns(struct kvm_vcpu *vcpu)
{
        unsigned int old, val, shrink;

        old = val = vcpu->halt_poll_ns;
        shrink = READ_ONCE(halt_poll_ns_shrink);
        if (shrink == 0)
                val = 0;
        else
                val /= shrink;

        vcpu->halt_poll_ns = val;
        trace_kvm_halt_poll_ns_shrink(vcpu->vcpu_id, val, old);
}

static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu)
{
        int ret = -EINTR;
        int idx = srcu_read_lock(&vcpu->kvm->srcu);

        if (kvm_arch_vcpu_runnable(vcpu)) {
                kvm_make_request(KVM_REQ_UNHALT, vcpu);
                goto out;
        }
        if (kvm_cpu_has_pending_timer(vcpu))
                goto out;
        if (signal_pending(current))
                goto out;

        ret = 0;
out:
        srcu_read_unlock(&vcpu->kvm->srcu, idx);
        return ret;
}

static inline void
update_halt_poll_stats(struct kvm_vcpu *vcpu, u64 poll_ns, bool waited)
{
        if (waited)
                vcpu->stat.halt_poll_fail_ns += poll_ns;
        else
                vcpu->stat.halt_poll_success_ns += poll_ns;
}

/*
 * The vCPU has executed a HLT instruction with in-kernel mode enabled.
 */
void kvm_vcpu_block(struct kvm_vcpu *vcpu)
{
        ktime_t start, cur, poll_end;
        bool waited = false;
        u64 block_ns;

        kvm_arch_vcpu_blocking(vcpu);

        start = cur = poll_end = ktime_get();
        if (vcpu->halt_poll_ns && !kvm_arch_no_poll(vcpu)) {
                ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns);

                ++vcpu->stat.halt_attempted_poll;
                do {
                        /*
                         * This sets KVM_REQ_UNHALT if an interrupt
                         * arrives.
                         */
                        if (kvm_vcpu_check_block(vcpu) < 0) {
                                ++vcpu->stat.halt_successful_poll;
                                if (!vcpu_valid_wakeup(vcpu))
                                        ++vcpu->stat.halt_poll_invalid;
                                goto out;
                        }
                        poll_end = cur = ktime_get();
                } while (single_task_running() && ktime_before(cur, stop));
        }

        prepare_to_rcuwait(&vcpu->wait);
        for (;;) {
                set_current_state(TASK_INTERRUPTIBLE);

                if (kvm_vcpu_check_block(vcpu) < 0)
                        break;

                waited = true;
                schedule();
        }
        finish_rcuwait(&vcpu->wait);
        cur = ktime_get();
out:
        kvm_arch_vcpu_unblocking(vcpu);
        block_ns = ktime_to_ns(cur) - ktime_to_ns(start);

        update_halt_poll_stats(
                vcpu, ktime_to_ns(ktime_sub(poll_end, start)), waited);

        if (!kvm_arch_no_poll(vcpu)) {
                if (!vcpu_valid_wakeup(vcpu)) {
                        shrink_halt_poll_ns(vcpu);
                } else if (vcpu->kvm->max_halt_poll_ns) {
                        if (block_ns <= vcpu->halt_poll_ns)
                                ;
                        /* we had a long block, shrink polling */
                        else if (vcpu->halt_poll_ns &&
                                        block_ns > vcpu->kvm->max_halt_poll_ns)
                                shrink_halt_poll_ns(vcpu);
                        /* we had a short halt and our poll time is too small */
                        else if (vcpu->halt_poll_ns < vcpu->kvm->max_halt_poll_ns &&
                                        block_ns < vcpu->kvm->max_halt_poll_ns)
                                grow_halt_poll_ns(vcpu);
                } else {
                        vcpu->halt_poll_ns = 0;
                }
        }

        trace_kvm_vcpu_wakeup(block_ns, waited, vcpu_valid_wakeup(vcpu));
        kvm_arch_vcpu_block_finish(vcpu);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_block);

bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu)
{
        struct rcuwait *waitp;

        waitp = kvm_arch_vcpu_get_wait(vcpu);
        if (rcuwait_wake_up(waitp)) {
                WRITE_ONCE(vcpu->ready, true);
                ++vcpu->stat.halt_wakeup;
                return true;
        }

        return false;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_wake_up);

#ifndef CONFIG_S390
/*
 * Kick a sleeping VCPU, or a guest VCPU in guest mode, into host kernel mode.
 */
void kvm_vcpu_kick(struct kvm_vcpu *vcpu)
{
        int me;
        int cpu = vcpu->cpu;

        if (kvm_vcpu_wake_up(vcpu))
                return;

        me = get_cpu();
        if (cpu != me && (unsigned)cpu < nr_cpu_ids && cpu_online(cpu))
                if (kvm_arch_vcpu_should_kick(vcpu))
                        smp_send_reschedule(cpu);
        put_cpu();
}
EXPORT_SYMBOL_GPL(kvm_vcpu_kick);
#endif /* !CONFIG_S390 */

int kvm_vcpu_yield_to(struct kvm_vcpu *target)
{
        struct pid *pid;
        struct task_struct *task = NULL;
        int ret = 0;

        rcu_read_lock();
        pid = rcu_dereference(target->pid);
        if (pid)
                task = get_pid_task(pid, PIDTYPE_PID);
        rcu_read_unlock();
        if (!task)
                return ret;
        ret = yield_to(task, 1);
        put_task_struct(task);

        return ret;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_yield_to);

/*
 * Helper that checks whether a VCPU is eligible for directed yield.
 * Most eligible candidate to yield is decided by following heuristics:
 *
 *  (a) VCPU which has not done pl-exit or cpu relax intercepted recently
 *  (preempted lock holder), indicated by @in_spin_loop.
 *  Set at the beginning and cleared at the end of interception/PLE handler.
 *
 *  (b) VCPU which has done pl-exit/ cpu relax intercepted but did not get
 *  chance last time (mostly it has become eligible now since we have probably
 *  yielded to lockholder in last iteration. This is done by toggling
 *  @dy_eligible each time a VCPU checked for eligibility.)
 *
 *  Yielding to a recently pl-exited/cpu relax intercepted VCPU before yielding
 *  to preempted lock-holder could result in wrong VCPU selection and CPU
 *  burning. Giving priority for a potential lock-holder increases lock
 *  progress.
 *
 *  Since algorithm is based on heuristics, accessing another VCPU data without
 *  locking does not harm. It may result in trying to yield to  same VCPU, fail
 *  and continue with next VCPU and so on.
 */
static bool kvm_vcpu_eligible_for_directed_yield(struct kvm_vcpu *vcpu)
{
#ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
        bool eligible;

        eligible = !vcpu->spin_loop.in_spin_loop ||
                    vcpu->spin_loop.dy_eligible;

        if (vcpu->spin_loop.in_spin_loop)
                kvm_vcpu_set_dy_eligible(vcpu, !vcpu->spin_loop.dy_eligible);

        return eligible;
#else
        return true;
#endif
}

/*
 * Unlike kvm_arch_vcpu_runnable, this function is called outside
 * a vcpu_load/vcpu_put pair.  However, for most architectures
 * kvm_arch_vcpu_runnable does not require vcpu_load.
 */
bool __weak kvm_arch_dy_runnable(struct kvm_vcpu *vcpu)
{
        return kvm_arch_vcpu_runnable(vcpu);
}

static bool vcpu_dy_runnable(struct kvm_vcpu *vcpu)
{
        if (kvm_arch_dy_runnable(vcpu))
                return true;

#ifdef CONFIG_KVM_ASYNC_PF
        if (!list_empty_careful(&vcpu->async_pf.done))
                return true;
#endif

        return false;
}

void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode)
{
        struct kvm *kvm = me->kvm;
        struct kvm_vcpu *vcpu;
        int last_boosted_vcpu = me->kvm->last_boosted_vcpu;
        int yielded = 0;
        int try = 3;
        int pass;
        int i;

        kvm_vcpu_set_in_spin_loop(me, true);
        /*
         * We boost the priority of a VCPU that is runnable but not
         * currently running, because it got preempted by something
         * else and called schedule in __vcpu_run.  Hopefully that
         * VCPU is holding the lock that we need and will release it.
         * We approximate round-robin by starting at the last boosted VCPU.
         */
        for (pass = 0; pass < 2 && !yielded && try; pass++) {
                kvm_for_each_vcpu(i, vcpu, kvm) {
                        if (!pass && i <= last_boosted_vcpu) {
                                i = last_boosted_vcpu;
                                continue;
                        } else if (pass && i > last_boosted_vcpu)
                                break;
                        if (!READ_ONCE(vcpu->ready))
                                continue;
                        if (vcpu == me)
                                continue;
                        if (rcuwait_active(&vcpu->wait) &&
                            !vcpu_dy_runnable(vcpu))
                                continue;
                        if (READ_ONCE(vcpu->preempted) && yield_to_kernel_mode &&
                                !kvm_arch_vcpu_in_kernel(vcpu))
                                continue;
                        if (!kvm_vcpu_eligible_for_directed_yield(vcpu))
                                continue;

                        yielded = kvm_vcpu_yield_to(vcpu);
                        if (yielded > 0) {
                                kvm->last_boosted_vcpu = i;
                                break;
                        } else if (yielded < 0) {
                                try--;
                                if (!try)
                                        break;
                        }
                }
        }
        kvm_vcpu_set_in_spin_loop(me, false);