// SPDX-License-Identifier: GPL-2.0
/*
 * KVM coalesced MMIO
 *
 * Copyright (c) 2008 Bull S.A.S.
 * Copyright 2009 Red Hat, Inc. and/or its affiliates.
 *
 *  Author: Laurent Vivier <Laurent.Vivier@bull.net>
 *
 */

#include <kvm/iodev.h>

#include <linux/kvm_host.h>
#include <linux/slab.h>
#include <linux/kvm.h>

#include "coalesced_mmio.h"

static inline struct kvm_coalesced_mmio_dev *to_mmio(struct kvm_io_device *dev)
{
        return container_of(dev, struct kvm_coalesced_mmio_dev, dev);
}

static int coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev *dev,
                                   gpa_t addr, int len)
{
        /* is it in a batchable area ?
         * (addr,len) is fully included in
         * (zone->addr, zone->size)
         */
        if (len < 0)
                return 0;
        if (addr + len < addr)
                return 0;
        if (addr < dev->zone.addr)
                return 0;
        if (addr + len > dev->zone.addr + dev->zone.size)
                return 0;
        return 1;
}

static int coalesced_mmio_has_room(struct kvm_coalesced_mmio_dev *dev, u32 last)
{
        struct kvm_coalesced_mmio_ring *ring;
        unsigned avail;

        /* Are we able to batch it ? */

        /* last is the first free entry
         * check if we don't meet the first used entry
         * there is always one unused entry in the buffer
         */
        ring = dev->kvm->coalesced_mmio_ring;
        avail = (ring->first - last - 1) % KVM_COALESCED_MMIO_MAX;
        if (avail == 0) {
                /* full */
                return 0;
        }

        return 1;
}

static int coalesced_mmio_write(struct kvm_vcpu *vcpu,
                                struct kvm_io_device *this, gpa_t addr,
                                int len, const void *val)
{
        struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
        struct kvm_coalesced_mmio_ring *ring = dev->kvm->coalesced_mmio_ring;
        __u32 insert;

        if (!coalesced_mmio_in_range(dev, addr, len))
                return -EOPNOTSUPP;

        spin_lock(&dev->kvm->ring_lock);

        insert = READ_ONCE(ring->last);
        if (!coalesced_mmio_has_room(dev, insert) ||
            insert >= KVM_COALESCED_MMIO_MAX) {
                spin_unlock(&dev->kvm->ring_lock);
                return -EOPNOTSUPP;
        }

        /* copy data in first free entry of the ring */

        ring->coalesced_mmio[insert].phys_addr = addr;
        ring->coalesced_mmio[insert].len = len;
        memcpy(ring->coalesced_mmio[insert].data, val, len);
        ring->coalesced_mmio[insert].pio = dev->zone.pio;
        smp_wmb();
        ring->last = (insert + 1) % KVM_COALESCED_MMIO_MAX;
        spin_unlock(&dev->kvm->ring_lock);
        return 0;
}

static void coalesced_mmio_destructor(struct kvm_io_device *this)
{
        struct kvm_coalesced_mmio_dev *dev = to_mmio(this);

        list_del(&dev->list);

        kfree(dev);
}

static const struct kvm_io_device_ops coalesced_mmio_ops = {
        .write      = coalesced_mmio_write,
        .destructor = coalesced_mmio_destructor,
};

int kvm_coalesced_mmio_init(struct kvm *kvm)
{
        struct page *page;

        page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
        if (!page)
                return -ENOMEM;

        kvm->coalesced_mmio_ring = page_address(page);

        /*
         * We're using this spinlock to sync access to the coalesced ring.
         * The list doesn't need its own lock since device registration and
         * unregistration should only happen when kvm->slots_lock is held.
         */
        spin_lock_init(&kvm->ring_lock);
        INIT_LIST_HEAD(&kvm->coalesced_zones);

        return 0;
}

void kvm_coalesced_mmio_free(struct kvm *kvm)
{
        if (kvm->coalesced_mmio_ring)
                free_page((unsigned long)kvm->coalesced_mmio_ring);
}

int kvm_vm_ioctl_register_coalesced_mmio(struct kvm *kvm,
                                         struct kvm_coalesced_mmio_zone *zone)
{
        int ret;
        struct kvm_coalesced_mmio_dev *dev;

        if (zone->pio != 1 && zone->pio != 0)
                return -EINVAL;

        dev = kzalloc(sizeof(struct kvm_coalesced_mmio_dev),
                      GFP_KERNEL_ACCOUNT);
        if (!dev)
                return -ENOMEM;

        kvm_iodevice_init(&dev->dev, &coalesced_mmio_ops);
        dev->kvm = kvm;
        dev->zone = *zone;

        mutex_lock(&kvm->slots_lock);
        ret = kvm_io_bus_register_dev(kvm,
                                zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS,
                                zone->addr, zone->size, &dev->dev);
        if (ret < 0)
                goto out_free_dev;
        list_add_tail(&dev->list, &kvm->coalesced_zones);
        mutex_unlock(&kvm->slots_lock);

        return 0;

out_free_dev:
        mutex_unlock(&kvm->slots_lock);
        kfree(dev);

        return ret;
}

int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
                                           struct kvm_coalesced_mmio_zone *zone)
{
        struct kvm_coalesced_mmio_dev *dev, *tmp;
        int r;

        if (zone->pio != 1 && zone->pio != 0)
                return -EINVAL;

        mutex_lock(&kvm->slots_lock);

        list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list) {
                if (zone->pio == dev->zone.pio &&
                    coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
                        r = kvm_io_bus_unregister_dev(kvm,
                                zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS, &dev->dev);

                        /*
                         * On failure, unregister destroys all devices on the
                         * bus _except_ the target device, i.e. coalesced_zones
                         * has been modified.  No need to restart the walk as
                         * there aren't any zones left.
                         */
                        if (r)
                                break;
                        kvm_iodevice_destructor(&dev->dev);
                }
        }

        mutex_unlock(&kvm->slots_lock);

        /*
         * Ignore the result of kvm_io_bus_unregister_dev(), from userspace's
         * perspective, the coalesced MMIO is most definitely unregistered.
         */
        return 0;
}