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         int ret;
 114
 115         ret = -ENOMEM;
 116         page = alloc_page(GFP_KERNEL | __GFP_ZERO);
 117         if (!page)
 118                 goto out_err;
 119
 120         ret = 0;
 121         kvm->coalesced_mmio_ring = page_address(page);
 122
 123         /*
 124          * We're using this spinlock to sync access to the coalesced ring.
 125          * The list doesn't need it's own lock since device registration and
 126          * unregistration should only happen when kvm->slots_lock is held.
 127          */
 128         spin_lock_init(&kvm->ring_lock);
 129         INIT_LIST_HEAD(&kvm->coalesced_zones);
 130
 131 out_err:
 132         return ret;
 133 }
 134
 135 void kvm_coalesced_mmio_free(struct kvm *kvm)
 136 {
 137         if (kvm->coalesced_mmio_ring)
 138                 free_page((unsigned long)kvm->coalesced_mmio_ring);
 139 }
 140
 141 int kvm_vm_ioctl_register_coalesced_mmio(struct kvm *kvm,
 142                                          struct kvm_coalesced_mmio_zone *zone)
 143 {
 144         int ret;
 145         struct kvm_coalesced_mmio_dev *dev;
 146
 147         if (zone->pio != 1 && zone->pio != 0)
 148                 return -EINVAL;
 149
 150         dev = kzalloc(sizeof(struct kvm_coalesced_mmio_dev),
 151                       GFP_KERNEL_ACCOUNT);
 152         if (!dev)
 153                 return -ENOMEM;
 154
 155         kvm_iodevice_init(&dev->dev, &coalesced_mmio_ops);
 156         dev->kvm = kvm;
 157         dev->zone = *zone;
 158
 159         mutex_lock(&kvm->slots_lock);
 160         ret = kvm_io_bus_register_dev(kvm,
 161                                 zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS,
 162                                 zone->addr, zone->size, &dev->dev);
 163         if (ret < 0)
 164                 goto out_free_dev;
 165         list_add_tail(&dev->list, &kvm->coalesced_zones);
 166         mutex_unlock(&kvm->slots_lock);
 167
 168         return 0;
 169
 170 out_free_dev:
 171         mutex_unlock(&kvm->slots_lock);
 172         kfree(dev);
 173
 174         return ret;
 175 }
 176
 177 int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
 178                                            struct kvm_coalesced_mmio_zone *zone)
 179 {
 180         struct kvm_coalesced_mmio_dev *dev, *tmp;
 181
 182         if (zone->pio != 1 && zone->pio != 0)
 183                 return -EINVAL;
 184
 185         mutex_lock(&kvm->slots_lock);
 186
 187         list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list)
 188                 if (zone->pio == dev->zone.pio &&
 189                     coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
 190                         kvm_io_bus_unregister_dev(kvm,
 191                                 zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS, &dev->dev);
 192                         kvm_iodevice_destructor(&dev->dev);
 193                 }
 194
 195         mutex_unlock(&kvm->slots_lock);
 196
 197         return 0;
 198 }