xref: /openbmc/linux/virt/kvm/vfio.c (revision 8b235f2f)
1  /*
2   * VFIO-KVM bridge pseudo device
3   *
4   * Copyright (C) 2013 Red Hat, Inc.  All rights reserved.
5   *     Author: Alex Williamson <alex.williamson@redhat.com>
6   *
7   * This program is free software; you can redistribute it and/or modify
8   * it under the terms of the GNU General Public License version 2 as
9   * published by the Free Software Foundation.
10   */
11  
12  #include <linux/errno.h>
13  #include <linux/file.h>
14  #include <linux/kvm_host.h>
15  #include <linux/list.h>
16  #include <linux/module.h>
17  #include <linux/mutex.h>
18  #include <linux/slab.h>
19  #include <linux/uaccess.h>
20  #include <linux/vfio.h>
21  #include "vfio.h"
22  
23  struct kvm_vfio_group {
24  	struct list_head node;
25  	struct vfio_group *vfio_group;
26  };
27  
28  struct kvm_vfio {
29  	struct list_head group_list;
30  	struct mutex lock;
31  	bool noncoherent;
32  };
33  
34  static struct vfio_group *kvm_vfio_group_get_external_user(struct file *filep)
35  {
36  	struct vfio_group *vfio_group;
37  	struct vfio_group *(*fn)(struct file *);
38  
39  	fn = symbol_get(vfio_group_get_external_user);
40  	if (!fn)
41  		return ERR_PTR(-EINVAL);
42  
43  	vfio_group = fn(filep);
44  
45  	symbol_put(vfio_group_get_external_user);
46  
47  	return vfio_group;
48  }
49  
50  static void kvm_vfio_group_put_external_user(struct vfio_group *vfio_group)
51  {
52  	void (*fn)(struct vfio_group *);
53  
54  	fn = symbol_get(vfio_group_put_external_user);
55  	if (!fn)
56  		return;
57  
58  	fn(vfio_group);
59  
60  	symbol_put(vfio_group_put_external_user);
61  }
62  
63  static bool kvm_vfio_group_is_coherent(struct vfio_group *vfio_group)
64  {
65  	long (*fn)(struct vfio_group *, unsigned long);
66  	long ret;
67  
68  	fn = symbol_get(vfio_external_check_extension);
69  	if (!fn)
70  		return false;
71  
72  	ret = fn(vfio_group, VFIO_DMA_CC_IOMMU);
73  
74  	symbol_put(vfio_external_check_extension);
75  
76  	return ret > 0;
77  }
78  
79  /*
80   * Groups can use the same or different IOMMU domains.  If the same then
81   * adding a new group may change the coherency of groups we've previously
82   * been told about.  We don't want to care about any of that so we retest
83   * each group and bail as soon as we find one that's noncoherent.  This
84   * means we only ever [un]register_noncoherent_dma once for the whole device.
85   */
86  static void kvm_vfio_update_coherency(struct kvm_device *dev)
87  {
88  	struct kvm_vfio *kv = dev->private;
89  	bool noncoherent = false;
90  	struct kvm_vfio_group *kvg;
91  
92  	mutex_lock(&kv->lock);
93  
94  	list_for_each_entry(kvg, &kv->group_list, node) {
95  		if (!kvm_vfio_group_is_coherent(kvg->vfio_group)) {
96  			noncoherent = true;
97  			break;
98  		}
99  	}
100  
101  	if (noncoherent != kv->noncoherent) {
102  		kv->noncoherent = noncoherent;
103  
104  		if (kv->noncoherent)
105  			kvm_arch_register_noncoherent_dma(dev->kvm);
106  		else
107  			kvm_arch_unregister_noncoherent_dma(dev->kvm);
108  	}
109  
110  	mutex_unlock(&kv->lock);
111  }
112  
113  static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
114  {
115  	struct kvm_vfio *kv = dev->private;
116  	struct vfio_group *vfio_group;
117  	struct kvm_vfio_group *kvg;
118  	int32_t __user *argp = (int32_t __user *)(unsigned long)arg;
119  	struct fd f;
120  	int32_t fd;
121  	int ret;
122  
123  	switch (attr) {
124  	case KVM_DEV_VFIO_GROUP_ADD:
125  		if (get_user(fd, argp))
126  			return -EFAULT;
127  
128  		f = fdget(fd);
129  		if (!f.file)
130  			return -EBADF;
131  
132  		vfio_group = kvm_vfio_group_get_external_user(f.file);
133  		fdput(f);
134  
135  		if (IS_ERR(vfio_group))
136  			return PTR_ERR(vfio_group);
137  
138  		mutex_lock(&kv->lock);
139  
140  		list_for_each_entry(kvg, &kv->group_list, node) {
141  			if (kvg->vfio_group == vfio_group) {
142  				mutex_unlock(&kv->lock);
143  				kvm_vfio_group_put_external_user(vfio_group);
144  				return -EEXIST;
145  			}
146  		}
147  
148  		kvg = kzalloc(sizeof(*kvg), GFP_KERNEL);
149  		if (!kvg) {
150  			mutex_unlock(&kv->lock);
151  			kvm_vfio_group_put_external_user(vfio_group);
152  			return -ENOMEM;
153  		}
154  
155  		list_add_tail(&kvg->node, &kv->group_list);
156  		kvg->vfio_group = vfio_group;
157  
158  		kvm_arch_start_assignment(dev->kvm);
159  
160  		mutex_unlock(&kv->lock);
161  
162  		kvm_vfio_update_coherency(dev);
163  
164  		return 0;
165  
166  	case KVM_DEV_VFIO_GROUP_DEL:
167  		if (get_user(fd, argp))
168  			return -EFAULT;
169  
170  		f = fdget(fd);
171  		if (!f.file)
172  			return -EBADF;
173  
174  		vfio_group = kvm_vfio_group_get_external_user(f.file);
175  		fdput(f);
176  
177  		if (IS_ERR(vfio_group))
178  			return PTR_ERR(vfio_group);
179  
180  		ret = -ENOENT;
181  
182  		mutex_lock(&kv->lock);
183  
184  		list_for_each_entry(kvg, &kv->group_list, node) {
185  			if (kvg->vfio_group != vfio_group)
186  				continue;
187  
188  			list_del(&kvg->node);
189  			kvm_vfio_group_put_external_user(kvg->vfio_group);
190  			kfree(kvg);
191  			ret = 0;
192  			break;
193  		}
194  
195  		kvm_arch_end_assignment(dev->kvm);
196  
197  		mutex_unlock(&kv->lock);
198  
199  		kvm_vfio_group_put_external_user(vfio_group);
200  
201  		kvm_vfio_update_coherency(dev);
202  
203  		return ret;
204  	}
205  
206  	return -ENXIO;
207  }
208  
209  static int kvm_vfio_set_attr(struct kvm_device *dev,
210  			     struct kvm_device_attr *attr)
211  {
212  	switch (attr->group) {
213  	case KVM_DEV_VFIO_GROUP:
214  		return kvm_vfio_set_group(dev, attr->attr, attr->addr);
215  	}
216  
217  	return -ENXIO;
218  }
219  
220  static int kvm_vfio_has_attr(struct kvm_device *dev,
221  			     struct kvm_device_attr *attr)
222  {
223  	switch (attr->group) {
224  	case KVM_DEV_VFIO_GROUP:
225  		switch (attr->attr) {
226  		case KVM_DEV_VFIO_GROUP_ADD:
227  		case KVM_DEV_VFIO_GROUP_DEL:
228  			return 0;
229  		}
230  
231  		break;
232  	}
233  
234  	return -ENXIO;
235  }
236  
237  static void kvm_vfio_destroy(struct kvm_device *dev)
238  {
239  	struct kvm_vfio *kv = dev->private;
240  	struct kvm_vfio_group *kvg, *tmp;
241  
242  	list_for_each_entry_safe(kvg, tmp, &kv->group_list, node) {
243  		kvm_vfio_group_put_external_user(kvg->vfio_group);
244  		list_del(&kvg->node);
245  		kfree(kvg);
246  		kvm_arch_end_assignment(dev->kvm);
247  	}
248  
249  	kvm_vfio_update_coherency(dev);
250  
251  	kfree(kv);
252  	kfree(dev); /* alloc by kvm_ioctl_create_device, free by .destroy */
253  }
254  
255  static int kvm_vfio_create(struct kvm_device *dev, u32 type);
256  
257  static struct kvm_device_ops kvm_vfio_ops = {
258  	.name = "kvm-vfio",
259  	.create = kvm_vfio_create,
260  	.destroy = kvm_vfio_destroy,
261  	.set_attr = kvm_vfio_set_attr,
262  	.has_attr = kvm_vfio_has_attr,
263  };
264  
265  static int kvm_vfio_create(struct kvm_device *dev, u32 type)
266  {
267  	struct kvm_device *tmp;
268  	struct kvm_vfio *kv;
269  
270  	/* Only one VFIO "device" per VM */
271  	list_for_each_entry(tmp, &dev->kvm->devices, vm_node)
272  		if (tmp->ops == &kvm_vfio_ops)
273  			return -EBUSY;
274  
275  	kv = kzalloc(sizeof(*kv), GFP_KERNEL);
276  	if (!kv)
277  		return -ENOMEM;
278  
279  	INIT_LIST_HEAD(&kv->group_list);
280  	mutex_init(&kv->lock);
281  
282  	dev->private = kv;
283  
284  	return 0;
285  }
286  
287  int kvm_vfio_ops_init(void)
288  {
289  	return kvm_register_device_ops(&kvm_vfio_ops, KVM_DEV_TYPE_VFIO);
290  }
291  
292  void kvm_vfio_ops_exit(void)
293  {
294  	kvm_unregister_device_ops(KVM_DEV_TYPE_VFIO);
295  }
296