virt/kvm/coalesced_mmio.c

   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
  19 static 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
  24 static 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
  42 static 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
  63 static 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
  90 static 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
  99 static const struct kvm_io_device_ops coalesced_mmio_ops = {
 100         .write      = coalesced_mmio_write,
 101         .destructor = coalesced_mmio_destructor,
 102 };
 103
 104 int 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
 125 out_err:
 126         return ret;
 127 }
 128
 129 void 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
 135 int 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 0;
 158
 159 out_free_dev:
 160         mutex_unlock(&kvm->slots_lock);
 161         kfree(dev);
 162
 163         return ret;
 164 }
 165
 166 int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
 167                                            struct kvm_coalesced_mmio_zone *zone)
 168 {
 169         struct kvm_coalesced_mmio_dev *dev, *tmp;
 170
 171         mutex_lock(&kvm->slots_lock);
 172
 173         list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list)
 174                 if (coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
 175                         kvm_io_bus_unregister_dev(kvm, KVM_MMIO_BUS, &dev->dev);
 176                         kvm_iodevice_destructor(&dev->dev);
 177                 }
 178
 179         mutex_unlock(&kvm->slots_lock);
 180
 181         return 0;
 182 }