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
to_mmio(struct kvm_io_device * dev)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
coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev * dev,gpa_t addr,int len)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
coalesced_mmio_write(struct kvm_vcpu * vcpu,struct kvm_io_device * this,gpa_t addr,int len,const void * val)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
coalesced_mmio_destructor(struct kvm_io_device * this)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
kvm_coalesced_mmio_init(struct kvm * kvm)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
kvm_coalesced_mmio_free(struct kvm * kvm)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
kvm_vm_ioctl_register_coalesced_mmio(struct kvm * kvm,struct kvm_coalesced_mmio_zone * zone)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
kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm * kvm,struct kvm_coalesced_mmio_zone * zone)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 }
192