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 <kvm/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, u32 last)
  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 - 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_vcpu *vcpu,
  64                                 struct kvm_io_device *this, gpa_t addr,
  65                                 int len, const void *val)
  66 {
  67         struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
  68         struct kvm_coalesced_mmio_ring *ring = dev->kvm->coalesced_mmio_ring;
  69         __u32 insert;
  70
  71         if (!coalesced_mmio_in_range(dev, addr, len))
  72                 return -EOPNOTSUPP;
  73
  74         spin_lock(&dev->kvm->ring_lock);
  75
  76         insert = READ_ONCE(ring->last);
  77         if (!coalesced_mmio_has_room(dev, insert) ||
  78             insert >= KVM_COALESCED_MMIO_MAX) {
  79                 spin_unlock(&dev->kvm->ring_lock);
  80                 return -EOPNOTSUPP;
  81         }
  82
  83         /* copy data in first free entry of the ring */
  84
  85         ring->coalesced_mmio[insert].phys_addr = addr;
  86         ring->coalesced_mmio[insert].len = len;
  87         memcpy(ring->coalesced_mmio[insert].data, val, len);
  88         smp_wmb();
  89         ring->last = (insert + 1) % KVM_COALESCED_MMIO_MAX;
  90         spin_unlock(&dev->kvm->ring_lock);
  91         return 0;
  92 }
  93
  94 static void coalesced_mmio_destructor(struct kvm_io_device *this)
  95 {
  96         struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
  97
  98         list_del(&dev->list);
  99
 100         kfree(dev);
 101 }
 102
 103 static const struct kvm_io_device_ops coalesced_mmio_ops = {
 104         .write      = coalesced_mmio_write,
 105         .destructor = coalesced_mmio_destructor,
 106 };
 107
 108 int kvm_coalesced_mmio_init(struct kvm *kvm)
 109 {
 110         struct page *page;
 111         int ret;
 112
 113         ret = -ENOMEM;
 114         page = alloc_page(GFP_KERNEL | __GFP_ZERO);
 115         if (!page)
 116                 goto out_err;
 117
 118         ret = 0;
 119         kvm->coalesced_mmio_ring = page_address(page);
 120
 121         /*
 122          * We're using this spinlock to sync access to the coalesced ring.
 123          * The list doesn't need it's own lock since device registration and
 124          * unregistration should only happen when kvm->slots_lock is held.
 125          */
 126         spin_lock_init(&kvm->ring_lock);
 127         INIT_LIST_HEAD(&kvm->coalesced_zones);
 128
 129 out_err:
 130         return ret;
 131 }
 132
 133 void kvm_coalesced_mmio_free(struct kvm *kvm)
 134 {
 135         if (kvm->coalesced_mmio_ring)
 136                 free_page((unsigned long)kvm->coalesced_mmio_ring);
 137 }
 138
 139 int kvm_vm_ioctl_register_coalesced_mmio(struct kvm *kvm,
 140                                          struct kvm_coalesced_mmio_zone *zone)
 141 {
 142         int ret;
 143         struct kvm_coalesced_mmio_dev *dev;
 144
 145         dev = kzalloc(sizeof(struct kvm_coalesced_mmio_dev), GFP_KERNEL);
 146         if (!dev)
 147                 return -ENOMEM;
 148
 149         kvm_iodevice_init(&dev->dev, &coalesced_mmio_ops);
 150         dev->kvm = kvm;
 151         dev->zone = *zone;
 152
 153         mutex_lock(&kvm->slots_lock);
 154         ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, zone->addr,
 155                                       zone->size, &dev->dev);
 156         if (ret < 0)
 157                 goto out_free_dev;
 158         list_add_tail(&dev->list, &kvm->coalesced_zones);
 159         mutex_unlock(&kvm->slots_lock);
 160
 161         return 0;
 162
 163 out_free_dev:
 164         mutex_unlock(&kvm->slots_lock);
 165         kfree(dev);
 166
 167         return ret;
 168 }
 169
 170 int 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 }