linux/virt/kvm/coalesced_mmio.c
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   1/*
   2 * KVM coalesced MMIO
   3 *
   4 * Copyright (c) 2008 Bull S.A.S.
   5 * Copyright 2009 Red Hat, Inc. and/or its affiliates.
   6 *
   7 *  Author: Laurent Vivier <Laurent.Vivier@bull.net>
   8 *
   9 */
  10
  11#include "iodev.h"
  12
  13#include <linux/kvm_host.h>
  14#include <linux/slab.h>
  15#include <linux/kvm.h>
  16
  17#include "coalesced_mmio.h"
  18
  19static inline struct kvm_coalesced_mmio_dev *to_mmio(struct kvm_io_device *dev)
  20{
  21        return container_of(dev, struct kvm_coalesced_mmio_dev, dev);
  22}
  23
  24static int coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev *dev,
  25                                   gpa_t addr, int len)
  26{
  27        /* is it in a batchable area ?
  28         * (addr,len) is fully included in
  29         * (zone->addr, zone->size)
  30         */
  31        if (len < 0)
  32                return 0;
  33        if (addr + len < addr)
  34                return 0;
  35        if (addr < dev->zone.addr)
  36                return 0;
  37        if (addr + len > dev->zone.addr + dev->zone.size)
  38                return 0;
  39        return 1;
  40}
  41
  42static int coalesced_mmio_has_room(struct kvm_coalesced_mmio_dev *dev)
  43{
  44        struct kvm_coalesced_mmio_ring *ring;
  45        unsigned avail;
  46
  47        /* Are we able to batch it ? */
  48
  49        /* last is the first free entry
  50         * check if we don't meet the first used entry
  51         * there is always one unused entry in the buffer
  52         */
  53        ring = dev->kvm->coalesced_mmio_ring;
  54        avail = (ring->first - ring->last - 1) % KVM_COALESCED_MMIO_MAX;
  55        if (avail == 0) {
  56                /* full */
  57                return 0;
  58        }
  59
  60        return 1;
  61}
  62
  63static int coalesced_mmio_write(struct kvm_io_device *this,
  64                                gpa_t addr, int len, const void *val)
  65{
  66        struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
  67        struct kvm_coalesced_mmio_ring *ring = dev->kvm->coalesced_mmio_ring;
  68
  69        if (!coalesced_mmio_in_range(dev, addr, len))
  70                return -EOPNOTSUPP;
  71
  72        spin_lock(&dev->kvm->ring_lock);
  73
  74        if (!coalesced_mmio_has_room(dev)) {
  75                spin_unlock(&dev->kvm->ring_lock);
  76                return -EOPNOTSUPP;
  77        }
  78
  79        /* copy data in first free entry of the ring */
  80
  81        ring->coalesced_mmio[ring->last].phys_addr = addr;
  82        ring->coalesced_mmio[ring->last].len = len;
  83        memcpy(ring->coalesced_mmio[ring->last].data, val, len);
  84        smp_wmb();
  85        ring->last = (ring->last + 1) % KVM_COALESCED_MMIO_MAX;
  86        spin_unlock(&dev->kvm->ring_lock);
  87        return 0;
  88}
  89
  90static void coalesced_mmio_destructor(struct kvm_io_device *this)
  91{
  92        struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
  93
  94        list_del(&dev->list);
  95
  96        kfree(dev);
  97}
  98
  99static const struct kvm_io_device_ops coalesced_mmio_ops = {
 100        .write      = coalesced_mmio_write,
 101        .destructor = coalesced_mmio_destructor,
 102};
 103
 104int kvm_coalesced_mmio_init(struct kvm *kvm)
 105{
 106        struct page *page;
 107        int ret;
 108
 109        ret = -ENOMEM;
 110        page = alloc_page(GFP_KERNEL | __GFP_ZERO);
 111        if (!page)
 112                goto out_err;
 113
 114        ret = 0;
 115        kvm->coalesced_mmio_ring = page_address(page);
 116
 117        /*
 118         * We're using this spinlock to sync access to the coalesced ring.
 119         * The list doesn't need it's own lock since device registration and
 120         * unregistration should only happen when kvm->slots_lock is held.
 121         */
 122        spin_lock_init(&kvm->ring_lock);
 123        INIT_LIST_HEAD(&kvm->coalesced_zones);
 124
 125out_err:
 126        return ret;
 127}
 128
 129void kvm_coalesced_mmio_free(struct kvm *kvm)
 130{
 131        if (kvm->coalesced_mmio_ring)
 132                free_page((unsigned long)kvm->coalesced_mmio_ring);
 133}
 134
 135int kvm_vm_ioctl_register_coalesced_mmio(struct kvm *kvm,
 136                                         struct kvm_coalesced_mmio_zone *zone)
 137{
 138        int ret;
 139        struct kvm_coalesced_mmio_dev *dev;
 140
 141        dev = kzalloc(sizeof(struct kvm_coalesced_mmio_dev), GFP_KERNEL);
 142        if (!dev)
 143                return -ENOMEM;
 144
 145        kvm_iodevice_init(&dev->dev, &coalesced_mmio_ops);
 146        dev->kvm = kvm;
 147        dev->zone = *zone;
 148
 149        mutex_lock(&kvm->slots_lock);
 150        ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, zone->addr,
 151                                      zone->size, &dev->dev);
 152        if (ret < 0)
 153                goto out_free_dev;
 154        list_add_tail(&dev->list, &kvm->coalesced_zones);
 155        mutex_unlock(&kvm->slots_lock);
 156
 157        return ret;
 158
 159out_free_dev:
 160        mutex_unlock(&kvm->slots_lock);
 161
 162        kfree(dev);
 163
 164        if (dev == NULL)
 165                return -ENXIO;
 166
 167        return 0;
 168}
 169
 170int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
 171                                           struct kvm_coalesced_mmio_zone *zone)
 172{
 173        struct kvm_coalesced_mmio_dev *dev, *tmp;
 174
 175        mutex_lock(&kvm->slots_lock);
 176
 177        list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list)
 178                if (coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
 179                        kvm_io_bus_unregister_dev(kvm, KVM_MMIO_BUS, &dev->dev);
 180                        kvm_iodevice_destructor(&dev->dev);
 181                }
 182
 183        mutex_unlock(&kvm->slots_lock);
 184
 185        return 0;
 186}
 187
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