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