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         smp_wmb();
  90         ring->last = (insert + 1) % KVM_COALESCED_MMIO_MAX;
  91         spin_unlock(&dev->kvm->ring_lock);
  92         return 0;
  93 }
  94
  95 static void coalesced_mmio_destructor(struct kvm_io_device *this)
  96 {
  97         struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
  98
  99         list_del(&dev->list);
 100
 101         kfree(dev);
 102 }
 103
 104 static const struct kvm_io_device_ops coalesced_mmio_ops = {
 105         .write      = coalesced_mmio_write,
 106         .destructor = coalesced_mmio_destructor,
 107 };
 108
 109 int kvm_coalesced_mmio_init(struct kvm *kvm)
 110 {
 111         struct page *page;
 112         int ret;
 113
 114         ret = -ENOMEM;
 115         page = alloc_page(GFP_KERNEL | __GFP_ZERO);
 116         if (!page)
 117                 goto out_err;
 118
 119         ret = 0;
 120         kvm->coalesced_mmio_ring = page_address(page);
 121
 122         /*
 123          * We're using this spinlock to sync access to the coalesced ring.
 124          * The list doesn't need it's own lock since device registration and
 125          * unregistration should only happen when kvm->slots_lock is held.
 126          */
 127         spin_lock_init(&kvm->ring_lock);
 128         INIT_LIST_HEAD(&kvm->coalesced_zones);
 129
 130 out_err:
 131         return ret;
 132 }
 133
 134 void kvm_coalesced_mmio_free(struct kvm *kvm)
 135 {
 136         if (kvm->coalesced_mmio_ring)
 137                 free_page((unsigned long)kvm->coalesced_mmio_ring);
 138 }
 139
 140 int kvm_vm_ioctl_register_coalesced_mmio(struct kvm *kvm,
 141                                          struct kvm_coalesced_mmio_zone *zone)
 142 {
 143         int ret;
 144         struct kvm_coalesced_mmio_dev *dev;
 145
 146         dev = kzalloc(sizeof(struct kvm_coalesced_mmio_dev), GFP_KERNEL);
 147         if (!dev)
 148                 return -ENOMEM;
 149
 150         kvm_iodevice_init(&dev->dev, &coalesced_mmio_ops);
 151         dev->kvm = kvm;
 152         dev->zone = *zone;
 153
 154         mutex_lock(&kvm->slots_lock);
 155         ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, zone->addr,
 156                                       zone->size, &dev->dev);
 157         if (ret < 0)
 158                 goto out_free_dev;
 159         list_add_tail(&dev->list, &kvm->coalesced_zones);
 160         mutex_unlock(&kvm->slots_lock);
 161
 162         return 0;
 163
 164 out_free_dev:
 165         mutex_unlock(&kvm->slots_lock);
 166         kfree(dev);
 167
 168         return ret;
 169 }
 170
 171 int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
 172                                            struct kvm_coalesced_mmio_zone *zone)
 173 {
 174         struct kvm_coalesced_mmio_dev *dev, *tmp;
 175
 176         mutex_lock(&kvm->slots_lock);
 177
 178         list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list)
 179                 if (coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
 180                         kvm_io_bus_unregister_dev(kvm, KVM_MMIO_BUS, &dev->dev);
 181                         kvm_iodevice_destructor(&dev->dev);
 182                 }
 183
 184         mutex_unlock(&kvm->slots_lock);
 185
 186         return 0;
 187 }