xref: /openbmc/linux/virt/kvm/coalesced_mmio.c (revision 5ea5ca3c)
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_has_room(struct kvm_coalesced_mmio_dev * dev,u32 last)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 
coalesced_mmio_write(struct kvm_vcpu * vcpu,struct kvm_io_device * this,gpa_t addr,int len,const void * val)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 
coalesced_mmio_destructor(struct kvm_io_device * this)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 
kvm_coalesced_mmio_init(struct kvm * kvm)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 
kvm_coalesced_mmio_free(struct kvm * kvm)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 
kvm_vm_ioctl_register_coalesced_mmio(struct kvm * kvm,struct kvm_coalesced_mmio_zone * zone)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 
kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm * kvm,struct kvm_coalesced_mmio_zone * zone)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 			 * On failure, unregister destroys all devices on the
191 			 * bus, including the target device. There's no need
192 			 * to restart the walk as there aren't any zones left.
193 			 */
194 			if (r)
195 				break;
196 		}
197 	}
198 
199 	mutex_unlock(&kvm->slots_lock);
200 
201 	/*
202 	 * Ignore the result of kvm_io_bus_unregister_dev(), from userspace's
203 	 * perspective, the coalesced MMIO is most definitely unregistered.
204 	 */
205 	return 0;
206 }
207