Root/drivers/xen/pcpu.c

1/******************************************************************************
2 * pcpu.c
3 * Management physical cpu in dom0, get pcpu info and provide sys interface
4 *
5 * Copyright (c) 2012 Intel Corporation
6 * Author: Liu, Jinsong <jinsong.liu@intel.com>
7 * Author: Jiang, Yunhong <yunhong.jiang@intel.com>
8 *
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License version 2
11 * as published by the Free Software Foundation; or, when distributed
12 * separately from the Linux kernel or incorporated into other
13 * software packages, subject to the following license:
14 *
15 * Permission is hereby granted, free of charge, to any person obtaining a copy
16 * of this source file (the "Software"), to deal in the Software without
17 * restriction, including without limitation the rights to use, copy, modify,
18 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
19 * and to permit persons to whom the Software is furnished to do so, subject to
20 * the following conditions:
21 *
22 * The above copyright notice and this permission notice shall be included in
23 * all copies or substantial portions of the Software.
24 *
25 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
26 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
27 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
28 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
29 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
30 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
31 * IN THE SOFTWARE.
32 */
33
34#include <linux/interrupt.h>
35#include <linux/spinlock.h>
36#include <linux/cpu.h>
37#include <linux/stat.h>
38#include <linux/capability.h>
39
40#include <xen/xen.h>
41#include <xen/xenbus.h>
42#include <xen/events.h>
43#include <xen/interface/platform.h>
44#include <asm/xen/hypervisor.h>
45#include <asm/xen/hypercall.h>
46
47#define XEN_PCPU "xen_cpu: "
48
49/*
50 * @cpu_id: Xen physical cpu logic number
51 * @flags: Xen physical cpu status flag
52 * - XEN_PCPU_FLAGS_ONLINE: cpu is online
53 * - XEN_PCPU_FLAGS_INVALID: cpu is not present
54 */
55struct pcpu {
56    struct list_head list;
57    struct device dev;
58    uint32_t cpu_id;
59    uint32_t flags;
60};
61
62static struct bus_type xen_pcpu_subsys = {
63    .name = "xen_cpu",
64    .dev_name = "xen_cpu",
65};
66
67static DEFINE_MUTEX(xen_pcpu_lock);
68
69static LIST_HEAD(xen_pcpus);
70
71static int xen_pcpu_down(uint32_t cpu_id)
72{
73    struct xen_platform_op op = {
74        .cmd = XENPF_cpu_offline,
75        .interface_version = XENPF_INTERFACE_VERSION,
76        .u.cpu_ol.cpuid = cpu_id,
77    };
78
79    return HYPERVISOR_dom0_op(&op);
80}
81
82static int xen_pcpu_up(uint32_t cpu_id)
83{
84    struct xen_platform_op op = {
85        .cmd = XENPF_cpu_online,
86        .interface_version = XENPF_INTERFACE_VERSION,
87        .u.cpu_ol.cpuid = cpu_id,
88    };
89
90    return HYPERVISOR_dom0_op(&op);
91}
92
93static ssize_t show_online(struct device *dev,
94               struct device_attribute *attr,
95               char *buf)
96{
97    struct pcpu *cpu = container_of(dev, struct pcpu, dev);
98
99    return sprintf(buf, "%u\n", !!(cpu->flags & XEN_PCPU_FLAGS_ONLINE));
100}
101
102static ssize_t __ref store_online(struct device *dev,
103                  struct device_attribute *attr,
104                  const char *buf, size_t count)
105{
106    struct pcpu *pcpu = container_of(dev, struct pcpu, dev);
107    unsigned long long val;
108    ssize_t ret;
109
110    if (!capable(CAP_SYS_ADMIN))
111        return -EPERM;
112
113    if (kstrtoull(buf, 0, &val) < 0)
114        return -EINVAL;
115
116    switch (val) {
117    case 0:
118        ret = xen_pcpu_down(pcpu->cpu_id);
119        break;
120    case 1:
121        ret = xen_pcpu_up(pcpu->cpu_id);
122        break;
123    default:
124        ret = -EINVAL;
125    }
126
127    if (ret >= 0)
128        ret = count;
129    return ret;
130}
131static DEVICE_ATTR(online, S_IRUGO | S_IWUSR, show_online, store_online);
132
133static bool xen_pcpu_online(uint32_t flags)
134{
135    return !!(flags & XEN_PCPU_FLAGS_ONLINE);
136}
137
138static void pcpu_online_status(struct xenpf_pcpuinfo *info,
139                   struct pcpu *pcpu)
140{
141    if (xen_pcpu_online(info->flags) &&
142       !xen_pcpu_online(pcpu->flags)) {
143        /* the pcpu is onlined */
144        pcpu->flags |= XEN_PCPU_FLAGS_ONLINE;
145        kobject_uevent(&pcpu->dev.kobj, KOBJ_ONLINE);
146    } else if (!xen_pcpu_online(info->flags) &&
147            xen_pcpu_online(pcpu->flags)) {
148        /* The pcpu is offlined */
149        pcpu->flags &= ~XEN_PCPU_FLAGS_ONLINE;
150        kobject_uevent(&pcpu->dev.kobj, KOBJ_OFFLINE);
151    }
152}
153
154static struct pcpu *get_pcpu(uint32_t cpu_id)
155{
156    struct pcpu *pcpu;
157
158    list_for_each_entry(pcpu, &xen_pcpus, list) {
159        if (pcpu->cpu_id == cpu_id)
160            return pcpu;
161    }
162
163    return NULL;
164}
165
166static void pcpu_release(struct device *dev)
167{
168    struct pcpu *pcpu = container_of(dev, struct pcpu, dev);
169
170    list_del(&pcpu->list);
171    kfree(pcpu);
172}
173
174static void unregister_and_remove_pcpu(struct pcpu *pcpu)
175{
176    struct device *dev;
177
178    if (!pcpu)
179        return;
180
181    dev = &pcpu->dev;
182    if (dev->id)
183        device_remove_file(dev, &dev_attr_online);
184
185    /* pcpu remove would be implicitly done */
186    device_unregister(dev);
187}
188
189static int register_pcpu(struct pcpu *pcpu)
190{
191    struct device *dev;
192    int err = -EINVAL;
193
194    if (!pcpu)
195        return err;
196
197    dev = &pcpu->dev;
198    dev->bus = &xen_pcpu_subsys;
199    dev->id = pcpu->cpu_id;
200    dev->release = pcpu_release;
201
202    err = device_register(dev);
203    if (err) {
204        pcpu_release(dev);
205        return err;
206    }
207
208    /*
209     * Xen never offline cpu0 due to several restrictions
210     * and assumptions. This basically doesn't add a sys control
211     * to user, one cannot attempt to offline BSP.
212     */
213    if (dev->id) {
214        err = device_create_file(dev, &dev_attr_online);
215        if (err) {
216            device_unregister(dev);
217            return err;
218        }
219    }
220
221    return 0;
222}
223
224static struct pcpu *create_and_register_pcpu(struct xenpf_pcpuinfo *info)
225{
226    struct pcpu *pcpu;
227    int err;
228
229    if (info->flags & XEN_PCPU_FLAGS_INVALID)
230        return ERR_PTR(-ENODEV);
231
232    pcpu = kzalloc(sizeof(struct pcpu), GFP_KERNEL);
233    if (!pcpu)
234        return ERR_PTR(-ENOMEM);
235
236    INIT_LIST_HEAD(&pcpu->list);
237    pcpu->cpu_id = info->xen_cpuid;
238    pcpu->flags = info->flags;
239
240    /* Need hold on xen_pcpu_lock before pcpu list manipulations */
241    list_add_tail(&pcpu->list, &xen_pcpus);
242
243    err = register_pcpu(pcpu);
244    if (err) {
245        pr_warning(XEN_PCPU "Failed to register pcpu%u\n",
246               info->xen_cpuid);
247        return ERR_PTR(-ENOENT);
248    }
249
250    return pcpu;
251}
252
253/*
254 * Caller should hold the xen_pcpu_lock
255 */
256static int sync_pcpu(uint32_t cpu, uint32_t *max_cpu)
257{
258    int ret;
259    struct pcpu *pcpu = NULL;
260    struct xenpf_pcpuinfo *info;
261    struct xen_platform_op op = {
262        .cmd = XENPF_get_cpuinfo,
263        .interface_version = XENPF_INTERFACE_VERSION,
264        .u.pcpu_info.xen_cpuid = cpu,
265    };
266
267    ret = HYPERVISOR_dom0_op(&op);
268    if (ret)
269        return ret;
270
271    info = &op.u.pcpu_info;
272    if (max_cpu)
273        *max_cpu = info->max_present;
274
275    pcpu = get_pcpu(cpu);
276
277    /*
278     * Only those at cpu present map has its sys interface.
279     */
280    if (info->flags & XEN_PCPU_FLAGS_INVALID) {
281        if (pcpu)
282            unregister_and_remove_pcpu(pcpu);
283        return 0;
284    }
285
286    if (!pcpu) {
287        pcpu = create_and_register_pcpu(info);
288        if (IS_ERR_OR_NULL(pcpu))
289            return -ENODEV;
290    } else
291        pcpu_online_status(info, pcpu);
292
293    return 0;
294}
295
296/*
297 * Sync dom0's pcpu information with xen hypervisor's
298 */
299static int xen_sync_pcpus(void)
300{
301    /*
302     * Boot cpu always have cpu_id 0 in xen
303     */
304    uint32_t cpu = 0, max_cpu = 0;
305    int err = 0;
306    struct pcpu *pcpu, *tmp;
307
308    mutex_lock(&xen_pcpu_lock);
309
310    while (!err && (cpu <= max_cpu)) {
311        err = sync_pcpu(cpu, &max_cpu);
312        cpu++;
313    }
314
315    if (err)
316        list_for_each_entry_safe(pcpu, tmp, &xen_pcpus, list)
317            unregister_and_remove_pcpu(pcpu);
318
319    mutex_unlock(&xen_pcpu_lock);
320
321    return err;
322}
323
324static void xen_pcpu_work_fn(struct work_struct *work)
325{
326    xen_sync_pcpus();
327}
328static DECLARE_WORK(xen_pcpu_work, xen_pcpu_work_fn);
329
330static irqreturn_t xen_pcpu_interrupt(int irq, void *dev_id)
331{
332    schedule_work(&xen_pcpu_work);
333    return IRQ_HANDLED;
334}
335
336static int __init xen_pcpu_init(void)
337{
338    int irq, ret;
339
340    if (!xen_initial_domain())
341        return -ENODEV;
342
343    irq = bind_virq_to_irqhandler(VIRQ_PCPU_STATE, 0,
344                      xen_pcpu_interrupt, 0,
345                      "xen-pcpu", NULL);
346    if (irq < 0) {
347        pr_warning(XEN_PCPU "Failed to bind pcpu virq\n");
348        return irq;
349    }
350
351    ret = subsys_system_register(&xen_pcpu_subsys, NULL);
352    if (ret) {
353        pr_warning(XEN_PCPU "Failed to register pcpu subsys\n");
354        goto err1;
355    }
356
357    ret = xen_sync_pcpus();
358    if (ret) {
359        pr_warning(XEN_PCPU "Failed to sync pcpu info\n");
360        goto err2;
361    }
362
363    return 0;
364
365err2:
366    bus_unregister(&xen_pcpu_subsys);
367err1:
368    unbind_from_irqhandler(irq, NULL);
369    return ret;
370}
371arch_initcall(xen_pcpu_init);
372

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