coalesced_mmio.c

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/*
 * KVM coalesced MMIO
 *
 * Copyright (c) 2008 Bull S.A.S.
 * Copyright 2009 Red Hat, Inc. and/or its affiliates.
 *
 *  Author: Laurent Vivier <[email protected]>
 *
 */

#include "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)
{
    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 - ring->last - 1) % KVM_COALESCED_MMIO_MAX;
    if (avail == 0) {
        /* full */
        return 0;
    }

    return 1;
}

static int coalesced_mmio_write(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;

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

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

    if (!coalesced_mmio_has_room(dev)) {
        spin_unlock(&dev->kvm->ring_lock);
        return -EOPNOTSUPP;
    }

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

    ring->coalesced_mmio[ring->last].phys_addr = addr;
    ring->coalesced_mmio[ring->last].len = len;
    memcpy(ring->coalesced_mmio[ring->last].data, val, len);
    smp_wmb();
    ring->last = (ring->last + 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;
    int ret;

    ret = -ENOMEM;
    page = alloc_page(GFP_KERNEL | __GFP_ZERO);
    if (!page)
        goto out_err;

    ret = 0;
    kvm->coalesced_mmio_ring = page_address(page);

    /*
     * We're using this spinlock to sync access to the coalesced ring.
     * The list doesn't need it's 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);

out_err:
    return ret;
}

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;

    dev = kzalloc(sizeof(struct kvm_coalesced_mmio_dev), GFP_KERNEL);
    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, 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 ret;

out_free_dev:
    mutex_unlock(&kvm->slots_lock);

    kfree(dev);

    if (dev == NULL)
        return -ENXIO;

    return 0;
}

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

    mutex_lock(&kvm->slots_lock);

    list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list)
        if (coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
            kvm_io_bus_unregister_dev(kvm, KVM_MMIO_BUS, &dev->dev);
            kvm_iodevice_destructor(&dev->dev);
        }

    mutex_unlock(&kvm->slots_lock);

    return 0;
}