summaryrefslogtreecommitdiffstats
path: root/drivers/s390/kvm/kvm_virtio.c
blob: 47a7e6200b262f660c4471cc8c23bfccd32203c2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
/*
 * kvm_virtio.c - virtio for kvm on s390
 *
 * Copyright IBM Corp. 2008
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License (version 2 only)
 * as published by the Free Software Foundation.
 *
 *    Author(s): Christian Borntraeger <borntraeger@de.ibm.com>
 */

#include <linux/init.h>
#include <linux/bootmem.h>
#include <linux/err.h>
#include <linux/virtio.h>
#include <linux/virtio_config.h>
#include <linux/interrupt.h>
#include <linux/virtio_ring.h>
#include <linux/pfn.h>
#include <asm/io.h>
#include <asm/kvm_para.h>
#include <asm/kvm_virtio.h>
#include <asm/setup.h>
#include <asm/s390_ext.h>

#define VIRTIO_SUBCODE_64 0x0D00

/*
 * The pointer to our (page) of device descriptions.
 */
static void *kvm_devices;

/*
 * Unique numbering for kvm devices.
 */
static unsigned int dev_index;

struct kvm_device {
	struct virtio_device vdev;
	struct kvm_device_desc *desc;
};

#define to_kvmdev(vd) container_of(vd, struct kvm_device, vdev)

/*
 * memory layout:
 * - kvm_device_descriptor
 *        struct kvm_device_desc
 * - configuration
 *        struct kvm_vqconfig
 * - feature bits
 * - config space
 */
static struct kvm_vqconfig *kvm_vq_config(const struct kvm_device_desc *desc)
{
	return (struct kvm_vqconfig *)(desc + 1);
}

static u8 *kvm_vq_features(const struct kvm_device_desc *desc)
{
	return (u8 *)(kvm_vq_config(desc) + desc->num_vq);
}

static u8 *kvm_vq_configspace(const struct kvm_device_desc *desc)
{
	return kvm_vq_features(desc) + desc->feature_len * 2;
}

/*
 * The total size of the config page used by this device (incl. desc)
 */
static unsigned desc_size(const struct kvm_device_desc *desc)
{
	return sizeof(*desc)
		+ desc->num_vq * sizeof(struct kvm_vqconfig)
		+ desc->feature_len * 2
		+ desc->config_len;
}

/*
 * This tests (and acknowleges) a feature bit.
 */
static bool kvm_feature(struct virtio_device *vdev, unsigned fbit)
{
	struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
	u8 *features;

	if (fbit / 8 > desc->feature_len)
		return false;

	features = kvm_vq_features(desc);
	if (!(features[fbit / 8] & (1 << (fbit % 8))))
		return false;

	/*
	 * We set the matching bit in the other half of the bitmap to tell the
	 * Host we want to use this feature.
	 */
	features[desc->feature_len + fbit / 8] |= (1 << (fbit % 8));
	return true;
}

/*
 * Reading and writing elements in config space
 */
static void kvm_get(struct virtio_device *vdev, unsigned int offset,
		   void *buf, unsigned len)
{
	struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;

	BUG_ON(offset + len > desc->config_len);
	memcpy(buf, kvm_vq_configspace(desc) + offset, len);
}

static void kvm_set(struct virtio_device *vdev, unsigned int offset,
		   const void *buf, unsigned len)
{
	struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;

	BUG_ON(offset + len > desc->config_len);
	memcpy(kvm_vq_configspace(desc) + offset, buf, len);
}

/*
 * The operations to get and set the status word just access
 * the status field of the device descriptor. set_status will also
 * make a hypercall to the host, to tell about status changes
 */
static u8 kvm_get_status(struct virtio_device *vdev)
{
	return to_kvmdev(vdev)->desc->status;
}

static void kvm_set_status(struct virtio_device *vdev, u8 status)
{
	BUG_ON(!status);
	to_kvmdev(vdev)->desc->status = status;
	kvm_hypercall1(KVM_S390_VIRTIO_SET_STATUS,
		       (unsigned long) to_kvmdev(vdev)->desc);
}

/*
 * To reset the device, we use the KVM_VIRTIO_RESET hypercall, using the
 * descriptor address. The Host will zero the status and all the
 * features.
 */
static void kvm_reset(struct virtio_device *vdev)
{
	kvm_hypercall1(KVM_S390_VIRTIO_RESET,
		       (unsigned long) to_kvmdev(vdev)->desc);
}

/*
 * When the virtio_ring code wants to notify the Host, it calls us here and we
 * make a hypercall.  We hand the address  of the virtqueue so the Host
 * knows which virtqueue we're talking about.
 */
static void kvm_notify(struct virtqueue *vq)
{
	struct kvm_vqconfig *config = vq->priv;

	kvm_hypercall1(KVM_S390_VIRTIO_NOTIFY, config->address);
}

/*
 * This routine finds the first virtqueue described in the configuration of
 * this device and sets it up.
 */
static struct virtqueue *kvm_find_vq(struct virtio_device *vdev,
				    unsigned index,
				    void (*callback)(struct virtqueue *vq))
{
	struct kvm_device *kdev = to_kvmdev(vdev);
	struct kvm_vqconfig *config;
	struct virtqueue *vq;
	int err;

	if (index >= kdev->desc->num_vq)
		return ERR_PTR(-ENOENT);

	config = kvm_vq_config(kdev->desc)+index;

	err = vmem_add_mapping(config->address,
			       vring_size(config->num, PAGE_SIZE));
	if (err)
		goto out;

	vq = vring_new_virtqueue(config->num, vdev, (void *) config->address,
				 kvm_notify, callback);
	if (!vq) {
		err = -ENOMEM;
		goto unmap;
	}

	/*
	 * register a callback token
	 * The host will sent this via the external interrupt parameter
	 */
	config->token = (u64) vq;

	vq->priv = config;
	return vq;
unmap:
	vmem_remove_mapping(config->address,
			    vring_size(config->num, PAGE_SIZE));
out:
	return ERR_PTR(err);
}

static void kvm_del_vq(struct virtqueue *vq)
{
	struct kvm_vqconfig *config = vq->priv;

	vring_del_virtqueue(vq);
	vmem_remove_mapping(config->address,
			    vring_size(config->num, PAGE_SIZE));
}

/*
 * The config ops structure as defined by virtio config
 */
static struct virtio_config_ops kvm_vq_configspace_ops = {
	.feature = kvm_feature,
	.get = kvm_get,
	.set = kvm_set,
	.get_status = kvm_get_status,
	.set_status = kvm_set_status,
	.reset = kvm_reset,
	.find_vq = kvm_find_vq,
	.del_vq = kvm_del_vq,
};

/*
 * The root device for the kvm virtio devices.
 * This makes them appear as /sys/devices/kvm_s390/0,1,2 not /sys/devices/0,1,2.
 */
static struct device kvm_root = {
	.parent = NULL,
	.bus_id = "kvm_s390",
};

/*
 * adds a new device and register it with virtio
 * appropriate drivers are loaded by the device model
 */
static void add_kvm_device(struct kvm_device_desc *d)
{
	struct kvm_device *kdev;

	kdev = kzalloc(sizeof(*kdev), GFP_KERNEL);
	if (!kdev) {
		printk(KERN_EMERG "Cannot allocate kvm dev %u\n",
		       dev_index++);
		return;
	}

	kdev->vdev.dev.parent = &kvm_root;
	kdev->vdev.index = dev_index++;
	kdev->vdev.id.device = d->type;
	kdev->vdev.config = &kvm_vq_configspace_ops;
	kdev->desc = d;

	if (register_virtio_device(&kdev->vdev) != 0) {
		printk(KERN_ERR "Failed to register kvm device %u\n",
		       kdev->vdev.index);
		kfree(kdev);
	}
}

/*
 * scan_devices() simply iterates through the device page.
 * The type 0 is reserved to mean "end of devices".
 */
static void scan_devices(void)
{
	unsigned int i;
	struct kvm_device_desc *d;

	for (i = 0; i < PAGE_SIZE; i += desc_size(d)) {
		d = kvm_devices + i;

		if (d->type == 0)
			break;

		add_kvm_device(d);
	}
}

/*
 * we emulate the request_irq behaviour on top of s390 extints
 */
static void kvm_extint_handler(u16 code)
{
	void *data = (void *) *(long *) __LC_PFAULT_INTPARM;
	u16 subcode = S390_lowcore.cpu_addr;

	if ((subcode & 0xff00) != VIRTIO_SUBCODE_64)
		return;

	vring_interrupt(0, data);
}

/*
 * Init function for virtio
 * devices are in a single page above top of "normal" mem
 */
static int __init kvm_devices_init(void)
{
	int rc;

	if (!MACHINE_IS_KVM)
		return -ENODEV;

	rc = device_register(&kvm_root);
	if (rc) {
		printk(KERN_ERR "Could not register kvm_s390 root device");
		return rc;
	}

	rc = vmem_add_mapping(PFN_PHYS(max_pfn), PAGE_SIZE);
	if (rc) {
		device_unregister(&kvm_root);
		return rc;
	}

	kvm_devices = (void *) PFN_PHYS(max_pfn);

	ctl_set_bit(0, 9);
	register_external_interrupt(0x2603, kvm_extint_handler);

	scan_devices();
	return 0;
}

/*
 * We do this after core stuff, but before the drivers.
 */
postcore_initcall(kvm_devices_init);
OpenPOWER on IntegriCloud