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_write(struct kvm_vcpu *vcpu,
  44                                 struct kvm_io_device *this, gpa_t addr,
  45                                 int len, const void *val)
  46 {
  47         struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
  48         struct kvm_coalesced_mmio_ring *ring = dev->kvm->coalesced_mmio_ring;
  49         __u32 insert;
  50
  51         if (!coalesced_mmio_in_range(dev, addr, len))
  52                 return -EOPNOTSUPP;
  53
  54         spin_lock(&dev->kvm->ring_lock);
  55
  56         /*
  57          * last is the index of the entry to fill.  Verify userspace hasn't
  58          * set last to be out of range, and that there is room in the ring.
  59          * Leave one entry free in the ring so that userspace can differentiate
  60          * between an empty ring and a full ring.
  61          */
  62         insert = READ_ONCE(ring->last);
  63         if (insert >= KVM_COALESCED_MMIO_MAX ||
  64             (insert + 1) % KVM_COALESCED_MMIO_MAX == READ_ONCE(ring->first)) {
  65                 spin_unlock(&dev->kvm->ring_lock);
  66                 return -EOPNOTSUPP;
  67         }
  68
  69         /* copy data in first free entry of the ring */
  70
  71         ring->coalesced_mmio[insert].phys_addr = addr;
  72         ring->coalesced_mmio[insert].len = len;
  73         memcpy(ring->coalesced_mmio[insert].data, val, len);
  74         ring->coalesced_mmio[insert].pio = dev->zone.pio;
  75         smp_wmb();
  76         ring->last = (insert + 1) % KVM_COALESCED_MMIO_MAX;
  77         spin_unlock(&dev->kvm->ring_lock);
  78         return 0;
  79 }
  80
  81 static void coalesced_mmio_destructor(struct kvm_io_device *this)
  82 {
  83         struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
  84
  85         list_del(&dev->list);
  86
  87         kfree(dev);
  88 }
  89
  90 static const struct kvm_io_device_ops coalesced_mmio_ops = {
  91         .write      = coalesced_mmio_write,
  92         .destructor = coalesced_mmio_destructor,
  93 };
  94
  95 int kvm_coalesced_mmio_init(struct kvm *kvm)
  96 {
  97         struct page *page;
  98
  99         page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
 100         if (!page)
 101                 return -ENOMEM;
 102
 103         kvm->coalesced_mmio_ring = page_address(page);
 104
 105         /*
 106          * We're using this spinlock to sync access to the coalesced ring.
 107          * The list doesn't need its own lock since device registration and
 108          * unregistration should only happen when kvm->slots_lock is held.
 109          */
 110         spin_lock_init(&kvm->ring_lock);
 111         INIT_LIST_HEAD(&kvm->coalesced_zones);
 112
 113         return 0;
 114 }
 115
 116 void kvm_coalesced_mmio_free(struct kvm *kvm)
 117 {
 118         if (kvm->coalesced_mmio_ring)
 119                 free_page((unsigned long)kvm->coalesced_mmio_ring);
 120 }
 121
 122 int kvm_vm_ioctl_register_coalesced_mmio(struct kvm *kvm,
 123                                          struct kvm_coalesced_mmio_zone *zone)
 124 {
 125         int ret;
 126         struct kvm_coalesced_mmio_dev *dev;
 127
 128         if (zone->pio != 1 && zone->pio != 0)
 129                 return -EINVAL;
 130
 131         dev = kzalloc(sizeof(struct kvm_coalesced_mmio_dev),
 132                       GFP_KERNEL_ACCOUNT);
 133         if (!dev)
 134                 return -ENOMEM;
 135
 136         kvm_iodevice_init(&dev->dev, &coalesced_mmio_ops);
 137         dev->kvm = kvm;
 138         dev->zone = *zone;
 139
 140         mutex_lock(&kvm->slots_lock);
 141         ret = kvm_io_bus_register_dev(kvm,
 142                                 zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS,
 143                                 zone->addr, zone->size, &dev->dev);
 144         if (ret < 0)
 145                 goto out_free_dev;
 146         list_add_tail(&dev->list, &kvm->coalesced_zones);
 147         mutex_unlock(&kvm->slots_lock);
 148
 149         return 0;
 150
 151 out_free_dev:
 152         mutex_unlock(&kvm->slots_lock);
 153         kfree(dev);
 154
 155         return ret;
 156 }
 157
 158 int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
 159                                            struct kvm_coalesced_mmio_zone *zone)
 160 {
 161         struct kvm_coalesced_mmio_dev *dev, *tmp;
 162         int r;
 163
 164         if (zone->pio != 1 && zone->pio != 0)
 165                 return -EINVAL;
 166
 167         mutex_lock(&kvm->slots_lock);
 168
 169         list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list) {
 170                 if (zone->pio == dev->zone.pio &&
 171                     coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
 172                         r = kvm_io_bus_unregister_dev(kvm,
 173                                 zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS, &dev->dev);
 174                         /*
 175                          * On failure, unregister destroys all devices on the
 176                          * bus, including the target device. There's no need
 177                          * to restart the walk as there aren't any zones left.
 178                          */
 179                         if (r)
 180                                 break;
 181                 }
 182         }
 183
 184         mutex_unlock(&kvm->slots_lock);
 185
 186         /*
 187          * Ignore the result of kvm_io_bus_unregister_dev(), from userspace's
 188          * perspective, the coalesced MMIO is most definitely unregistered.
 189          */
 190         return 0;
 191 }