// SPDX-License-Identifier: GPL-2.0-only
/*
 * kvm asynchronous fault support
 *
 * Copyright 2010 Red Hat, Inc.
 *
 * Author:
 *      Gleb Natapov <gleb@redhat.com>
 */

#include <linux/kvm_host.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/mmu_context.h>
#include <linux/sched/mm.h>

#include "async_pf.h"
#include <trace/events/kvm.h>

static struct kmem_cache *async_pf_cache;

int kvm_async_pf_init(void)
{
        async_pf_cache = KMEM_CACHE(kvm_async_pf, 0);

        if (!async_pf_cache)
                return -ENOMEM;

        return 0;
}

void kvm_async_pf_deinit(void)
{
        kmem_cache_destroy(async_pf_cache);
        async_pf_cache = NULL;
}

void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
{
        INIT_LIST_HEAD(&vcpu->async_pf.done);
        INIT_LIST_HEAD(&vcpu->async_pf.queue);
        spin_lock_init(&vcpu->async_pf.lock);
}

static void async_pf_execute(struct work_struct *work)
{
        struct kvm_async_pf *apf =
                container_of(work, struct kvm_async_pf, work);
        struct mm_struct *mm = apf->mm;
        struct kvm_vcpu *vcpu = apf->vcpu;
        unsigned long addr = apf->addr;
        gpa_t cr2_or_gpa = apf->cr2_or_gpa;
        int locked = 1;
        bool first;

        might_sleep();

        /*
         * This work is run asynchronously to the task which owns
         * mm and might be done in another context, so we must
         * access remotely.
         */
        mmap_read_lock(mm);
        get_user_pages_remote(mm, addr, 1, FOLL_WRITE, NULL, NULL,
                        &locked);
        if (locked)
                mmap_read_unlock(mm);

        if (IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
                kvm_arch_async_page_present(vcpu, apf);

        spin_lock(&vcpu->async_pf.lock);
        first = list_empty(&vcpu->async_pf.done);
        list_add_tail(&apf->link, &vcpu->async_pf.done);
        apf->vcpu = NULL;
        spin_unlock(&vcpu->async_pf.lock);

        if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
                kvm_arch_async_page_present_queued(vcpu);

        /*
         * apf may be freed by kvm_check_async_pf_completion() after
         * this point
         */

        trace_kvm_async_pf_completed(addr, cr2_or_gpa);

        rcuwait_wake_up(&vcpu->wait);

        mmput(mm);
        kvm_put_kvm(vcpu->kvm);
}

void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
{
        spin_lock(&vcpu->async_pf.lock);

        /* cancel outstanding work queue item */
        while (!list_empty(&vcpu->async_pf.queue)) {
                struct kvm_async_pf *work =
                        list_first_entry(&vcpu->async_pf.queue,
                                         typeof(*work), queue);
                list_del(&work->queue);

                /*
                 * We know it's present in vcpu->async_pf.done, do
                 * nothing here.
                 */
                if (!work->vcpu)
                        continue;

                spin_unlock(&vcpu->async_pf.lock);
#ifdef CONFIG_KVM_ASYNC_PF_SYNC
                flush_work(&work->work);
#else
                if (cancel_work_sync(&work->work)) {
                        mmput(work->mm);
                        kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */
                        kmem_cache_free(async_pf_cache, work);
                }
#endif
                spin_lock(&vcpu->async_pf.lock);
        }

        while (!list_empty(&vcpu->async_pf.done)) {
                struct kvm_async_pf *work =
                        list_first_entry(&vcpu->async_pf.done,
                                         typeof(*work), link);
                list_del(&work->link);
                kmem_cache_free(async_pf_cache, work);
        }
        spin_unlock(&vcpu->async_pf.lock);

        vcpu->async_pf.queued = 0;
}

void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
{
        struct kvm_async_pf *work;

        while (!list_empty_careful(&vcpu->async_pf.done) &&
              kvm_arch_can_dequeue_async_page_present(vcpu)) {
                spin_lock(&vcpu->async_pf.lock);
                work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
                                              link);
                list_del(&work->link);
                spin_unlock(&vcpu->async_pf.lock);

                kvm_arch_async_page_ready(vcpu, work);
                if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
                        kvm_arch_async_page_present(vcpu, work);

                list_del(&work->queue);
                vcpu->async_pf.queued--;
                kmem_cache_free(async_pf_cache, work);
        }
}

/*
 * Try to schedule a job to handle page fault asynchronously. Returns 'true' on
 * success, 'false' on failure (page fault has to be handled synchronously).
 */
bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
                        unsigned long hva, struct kvm_arch_async_pf *arch)
{
        struct kvm_async_pf *work;

        if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
                return false;

        /* Arch specific code should not do async PF in this case */
        if (unlikely(kvm_is_error_hva(hva)))
                return false;

        /*
         * do alloc nowait since if we are going to sleep anyway we
         * may as well sleep faulting in page
         */
        work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN);
        if (!work)
                return false;

        work->wakeup_all = false;
        work->vcpu = vcpu;
        work->cr2_or_gpa = cr2_or_gpa;
        work->addr = hva;
        work->arch = *arch;
        work->mm = current->mm;
        mmget(work->mm);
        kvm_get_kvm(work->vcpu->kvm);

        INIT_WORK(&work->work, async_pf_execute);

        list_add_tail(&work->queue, &vcpu->async_pf.queue);
        vcpu->async_pf.queued++;
        work->notpresent_injected = kvm_arch_async_page_not_present(vcpu, work);

        schedule_work(&work->work);

        return true;
}

int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
{
        struct kvm_async_pf *work;
        bool first;

        if (!list_empty_careful(&vcpu->async_pf.done))
                return 0;

        work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
        if (!work)
                return -ENOMEM;

        work->wakeup_all = true;
        INIT_LIST_HEAD(&work->queue); /* for list_del to work */

        spin_lock(&vcpu->async_pf.lock);
        first = list_empty(&vcpu->async_pf.done);
        list_add_tail(&work->link, &vcpu->async_pf.done);
        spin_unlock(&vcpu->async_pf.lock);

        if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
                kvm_arch_async_page_present_queued(vcpu);

        vcpu->async_pf.queued++;
        return 0;
}