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, u32 last)
  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 - 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         __u32 insert;
  71
  72         if (!coalesced_mmio_in_range(dev, addr, len))
  73                 return -EOPNOTSUPP;
  74
  75         spin_lock(&dev->kvm->ring_lock);
  76
  77         insert = READ_ONCE(ring->last);
  78         if (!coalesced_mmio_has_room(dev, insert) ||
  79             insert >= KVM_COALESCED_MMIO_MAX) {
  80                 spin_unlock(&dev->kvm->ring_lock);
  81                 return -EOPNOTSUPP;
  82         }
  83
  84         /* copy data in first free entry of the ring */
  85
  86         ring->coalesced_mmio[insert].phys_addr = addr;
  87         ring->coalesced_mmio[insert].len = len;
  88         memcpy(ring->coalesced_mmio[insert].data, val, len);
  89         ring->coalesced_mmio[insert].pio = dev->zone.pio;
  90         smp_wmb();
  91         ring->last = (insert + 1) % KVM_COALESCED_MMIO_MAX;
  92         spin_unlock(&dev->kvm->ring_lock);
  93         return 0;
  94 }
  95
  96 static void coalesced_mmio_destructor(struct kvm_io_device *this)
  97 {
  98         struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
  99
 100         list_del(&dev->list);
 101
 102         kfree(dev);
 103 }
 104
 105 static const struct kvm_io_device_ops coalesced_mmio_ops = {
 106         .write      = coalesced_mmio_write,
 107         .destructor = coalesced_mmio_destructor,
 108 };
 109
 110 int kvm_coalesced_mmio_init(struct kvm *kvm)
 111 {
 112         struct page *page;
 113
 114         page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
 115         if (!page)
 116                 return -ENOMEM;
 117
 118         kvm->coalesced_mmio_ring = page_address(page);
 119
 120         /*
 121          * We're using this spinlock to sync access to the coalesced ring.
 122          * The list doesn't need its own lock since device registration and
 123          * unregistration should only happen when kvm->slots_lock is held.
 124          */
 125         spin_lock_init(&kvm->ring_lock);
 126         INIT_LIST_HEAD(&kvm->coalesced_zones);
 127
 128         return 0;
 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         if (zone->pio != 1 && zone->pio != 0)
 144                 return -EINVAL;
 145
 146         dev = kzalloc(sizeof(struct kvm_coalesced_mmio_dev),
 147                       GFP_KERNEL_ACCOUNT);
 148         if (!dev)
 149                 return -ENOMEM;
 150
 151         kvm_iodevice_init(&dev->dev, &coalesced_mmio_ops);
 152         dev->kvm = kvm;
 153         dev->zone = *zone;
 154
 155         mutex_lock(&kvm->slots_lock);
 156         ret = kvm_io_bus_register_dev(kvm,
 157                                 zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS,
 158                                 zone->addr, zone->size, &dev->dev);
 159         if (ret < 0)
 160                 goto out_free_dev;
 161         list_add_tail(&dev->list, &kvm->coalesced_zones);
 162         mutex_unlock(&kvm->slots_lock);
 163
 164         return 0;
 165
 166 out_free_dev:
 167         mutex_unlock(&kvm->slots_lock);
 168         kfree(dev);
 169
 170         return ret;
 171 }
 172
 173 int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
 174                                            struct kvm_coalesced_mmio_zone *zone)
 175 {
 176         struct kvm_coalesced_mmio_dev *dev, *tmp;
 177         int r;
 178
 179         if (zone->pio != 1 && zone->pio != 0)
 180                 return -EINVAL;
 181
 182         mutex_lock(&kvm->slots_lock);
 183
 184         list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list) {
 185                 if (zone->pio == dev->zone.pio &&
 186                     coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
 187                         r = kvm_io_bus_unregister_dev(kvm,
 188                                 zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS, &dev->dev);
 189
 190                         /*
 191                          * On failure, unregister destroys all devices on the
 192                          * bus _except_ the target device, i.e. coalesced_zones
 193                          * has been modified.  No need to restart the walk as
 194                          * there aren't any zones left.
 195                          */
 196                         if (r)
 197                                 break;
 198                         kvm_iodevice_destructor(&dev->dev);
 199                 }
 200         }
 201
 202         mutex_unlock(&kvm->slots_lock);
 203
 204         /*
 205          * Ignore the result of kvm_io_bus_unregister_dev(), from userspace's
 206          * perspective, the coalesced MMIO is most definitely unregistered.
 207          */
 208         return 0;
 209 }