virt/kvm/coalesced_mmio.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * KVM coalesced MMIO
   4  *
   5  * Copyright (c) 2008 Bull S.A.S.
   6  * Copyright 2009 Red Hat, Inc. and/or its affiliates.
   7  *
   8  *  Author: Laurent Vivier <Laurent.Vivier@bull.net>
   9  *
  10  */
  11
  12 #include <kvm/iodev.h>
  13
  14 #include <linux/kvm_host.h>
  15 #include <linux/slab.h>
  16 #include <linux/kvm.h>
  17
  18 #include "coalesced_mmio.h"
  19
  20 static inline struct kvm_coalesced_mmio_dev *to_mmio(struct kvm_io_device *dev)
  21 {
  22         return container_of(dev, struct kvm_coalesced_mmio_dev, dev);
  23 }
  24
  25 static int coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev *dev,
  26                                    gpa_t addr, int len)
  27 {
  28         /* is it in a batchable area ?
  29          * (addr,len) is fully included in
  30          * (zone->addr, zone->size)
  31          */
  32         if (len < 0)
  33                 return 0;
  34         if (addr + len < addr)
  35                 return 0;
  36         if (addr < dev->zone.addr)
  37                 return 0;
  38         if (addr + len > dev->zone.addr + dev->zone.size)
  39                 return 0;
  40         return 1;
  41 }
  42
  43 static int coalesced_mmio_has_room(struct kvm_coalesced_mmio_dev *dev)
  44 {
  45         struct kvm_coalesced_mmio_ring *ring;
  46         unsigned avail;
  47
  48         /* Are we able to batch it ? */
  49
  50         /* last is the first free entry
  51          * check if we don't meet the first used entry
  52          * there is always one unused entry in the buffer
  53          */
  54         ring = dev->kvm->coalesced_mmio_ring;
  55         avail = (ring->first - ring->last - 1) % KVM_COALESCED_MMIO_MAX;
  56         if (avail == 0) {
  57                 /* full */
  58                 return 0;
  59         }
  60
  61         return 1;
  62 }
  63
  64 static int coalesced_mmio_write(struct kvm_vcpu *vcpu,
  65                                 struct kvm_io_device *this, gpa_t addr,
  66                                 int len, const void *val)
  67 {
  68         struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
  69         struct kvm_coalesced_mmio_ring *ring = dev->kvm->coalesced_mmio_ring;
  70
  71         if (!coalesced_mmio_in_range(dev, addr, len))
  72                 return -EOPNOTSUPP;
  73
  74         spin_lock(&dev->kvm->ring_lock);
  75
  76         if (!coalesced_mmio_has_room(dev)) {
  77                 spin_unlock(&dev->kvm->ring_lock);
  78                 return -EOPNOTSUPP;
  79         }
  80
  81         /* copy data in first free entry of the ring */
  82
  83         ring->coalesced_mmio[ring->last].phys_addr = addr;
  84         ring->coalesced_mmio[ring->last].len = len;
  85         memcpy(ring->coalesced_mmio[ring->last].data, val, len);
  86         smp_wmb();
  87         ring->last = (ring->last + 1) % KVM_COALESCED_MMIO_MAX;
  88         spin_unlock(&dev->kvm->ring_lock);
  89         return 0;
  90 }
  91
  92 static void coalesced_mmio_destructor(struct kvm_io_device *this)
  93 {
  94         struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
  95
  96         list_del(&dev->list);
  97
  98         kfree(dev);
  99 }
 100
 101 static const struct kvm_io_device_ops coalesced_mmio_ops = {
 102         .write      = coalesced_mmio_write,
 103         .destructor = coalesced_mmio_destructor,
 104 };
 105
 106 int kvm_coalesced_mmio_init(struct kvm *kvm)
 107 {
 108         struct page *page;
 109         int ret;
 110
 111         ret = -ENOMEM;
 112         page = alloc_page(GFP_KERNEL | __GFP_ZERO);
 113         if (!page)
 114                 goto out_err;
 115
 116         ret = 0;
 117         kvm->coalesced_mmio_ring = page_address(page);
 118
 119         /*
 120          * We're using this spinlock to sync access to the coalesced ring.
 121          * The list doesn't need it's own lock since device registration and
 122          * unregistration should only happen when kvm->slots_lock is held.
 123          */
 124         spin_lock_init(&kvm->ring_lock);
 125         INIT_LIST_HEAD(&kvm->coalesced_zones);
 126
 127 out_err:
 128         return ret;
 129 }
 130
 131 void kvm_coalesced_mmio_free(struct kvm *kvm)
 132 {
 133         if (kvm->coalesced_mmio_ring)
 134                 free_page((unsigned long)kvm->coalesced_mmio_ring);
 135 }
 136
 137 int kvm_vm_ioctl_register_coalesced_mmio(struct kvm *kvm,
 138                                          struct kvm_coalesced_mmio_zone *zone)
 139 {
 140         int ret;
 141         struct kvm_coalesced_mmio_dev *dev;
 142
 143         dev = kzalloc(sizeof(struct kvm_coalesced_mmio_dev), GFP_KERNEL);
 144         if (!dev)
 145                 return -ENOMEM;
 146
 147         kvm_iodevice_init(&dev->dev, &coalesced_mmio_ops);
 148         dev->kvm = kvm;
 149         dev->zone = *zone;
 150
 151         mutex_lock(&kvm->slots_lock);
 152         ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, zone->addr,
 153                                       zone->size, &dev->dev);
 154         if (ret < 0)
 155                 goto out_free_dev;
 156         list_add_tail(&dev->list, &kvm->coalesced_zones);
 157         mutex_unlock(&kvm->slots_lock);
 158
 159         return 0;
 160
 161 out_free_dev:
 162         mutex_unlock(&kvm->slots_lock);
 163         kfree(dev);
 164
 165         return ret;
 166 }
 167
 168 int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
 169                                            struct kvm_coalesced_mmio_zone *zone)
 170 {
 171         struct kvm_coalesced_mmio_dev *dev, *tmp;
 172
 173         mutex_lock(&kvm->slots_lock);
 174
 175         list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list)
 176                 if (coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
 177                         kvm_io_bus_unregister_dev(kvm, KVM_MMIO_BUS, &dev->dev);
 178                         kvm_iodevice_destructor(&dev->dev);
 179                 }
 180
 181         mutex_unlock(&kvm->slots_lock);
 182
 183         return 0;
 184 }