LXR linux/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#define pr_fmt(fmt) "xen_cpu: " fmt
  35
  36#include <linux/interrupt.h>
  37#include <linux/spinlock.h>
  38#include <linux/cpu.h>
  39#include <linux/stat.h>
  40#include <linux/capability.h>
  41
  42#include <xen/xen.h>
  43#include <xen/xenbus.h>
  44#include <xen/events.h>
  45#include <xen/interface/platform.h>
  46#include <asm/xen/hypervisor.h>
  47#include <asm/xen/hypercall.h>
  48
  49
  50/*
  51 * @cpu_id: Xen physical cpu logic number
  52 * @flags: Xen physical cpu status flag
  53 * - XEN_PCPU_FLAGS_ONLINE: cpu is online
  54 * - XEN_PCPU_FLAGS_INVALID: cpu is not present
  55 */
  56struct pcpu {
  57        struct list_head list;
  58        struct device dev;
  59        uint32_t cpu_id;
  60        uint32_t flags;
  61};
  62
  63static struct bus_type xen_pcpu_subsys = {
  64        .name = "xen_cpu",
  65        .dev_name = "xen_cpu",
  66};
  67
  68static DEFINE_MUTEX(xen_pcpu_lock);
  69
  70static LIST_HEAD(xen_pcpus);
  71
  72static int xen_pcpu_down(uint32_t cpu_id)
  73{
  74        struct xen_platform_op op = {
  75                .cmd                    = XENPF_cpu_offline,
  76                .interface_version      = XENPF_INTERFACE_VERSION,
  77                .u.cpu_ol.cpuid         = cpu_id,
  78        };
  79
  80        return HYPERVISOR_dom0_op(&op);
  81}
  82
  83static int xen_pcpu_up(uint32_t cpu_id)
  84{
  85        struct xen_platform_op op = {
  86                .cmd                    = XENPF_cpu_online,
  87                .interface_version      = XENPF_INTERFACE_VERSION,
  88                .u.cpu_ol.cpuid         = cpu_id,
  89        };
  90
  91        return HYPERVISOR_dom0_op(&op);
  92}
  93
  94static ssize_t show_online(struct device *dev,
  95                           struct device_attribute *attr,
  96                           char *buf)
  97{
  98        struct pcpu *cpu = container_of(dev, struct pcpu, dev);
  99
 100        return sprintf(buf, "%u\n", !!(cpu->flags & XEN_PCPU_FLAGS_ONLINE));
 101}
 102
 103static ssize_t __ref store_online(struct device *dev,
 104                                  struct device_attribute *attr,
 105                                  const char *buf, size_t count)
 106{
 107        struct pcpu *pcpu = container_of(dev, struct pcpu, dev);
 108        unsigned long long val;
 109        ssize_t ret;
 110
 111        if (!capable(CAP_SYS_ADMIN))
 112                return -EPERM;
 113
 114        if (kstrtoull(buf, 0, &val) < 0)
 115                return -EINVAL;
 116
 117        switch (val) {
 118        case 0:
 119                ret = xen_pcpu_down(pcpu->cpu_id);
 120                break;
 121        case 1:
 122                ret = xen_pcpu_up(pcpu->cpu_id);
 123                break;
 124        default:
 125                ret = -EINVAL;
 126        }
 127
 128        if (ret >= 0)
 129                ret = count;
 130        return ret;
 131}
 132static DEVICE_ATTR(online, S_IRUGO | S_IWUSR, show_online, store_online);
 133
 134static bool xen_pcpu_online(uint32_t flags)
 135{
 136        return !!(flags & XEN_PCPU_FLAGS_ONLINE);
 137}
 138
 139static void pcpu_online_status(struct xenpf_pcpuinfo *info,
 140                               struct pcpu *pcpu)
 141{
 142        if (xen_pcpu_online(info->flags) &&
 143           !xen_pcpu_online(pcpu->flags)) {
 144                /* the pcpu is onlined */
 145                pcpu->flags |= XEN_PCPU_FLAGS_ONLINE;
 146                kobject_uevent(&pcpu->dev.kobj, KOBJ_ONLINE);
 147        } else if (!xen_pcpu_online(info->flags) &&
 148                    xen_pcpu_online(pcpu->flags)) {
 149                /* The pcpu is offlined */
 150                pcpu->flags &= ~XEN_PCPU_FLAGS_ONLINE;
 151                kobject_uevent(&pcpu->dev.kobj, KOBJ_OFFLINE);
 152        }
 153}
 154
 155static struct pcpu *get_pcpu(uint32_t cpu_id)
 156{
 157        struct pcpu *pcpu;
 158
 159        list_for_each_entry(pcpu, &xen_pcpus, list) {
 160                if (pcpu->cpu_id == cpu_id)
 161                        return pcpu;
 162        }
 163
 164        return NULL;
 165}
 166
 167static void pcpu_release(struct device *dev)
 168{
 169        struct pcpu *pcpu = container_of(dev, struct pcpu, dev);
 170
 171        list_del(&pcpu->list);
 172        kfree(pcpu);
 173}
 174
 175static void unregister_and_remove_pcpu(struct pcpu *pcpu)
 176{
 177        struct device *dev;
 178
 179        if (!pcpu)
 180                return;
 181
 182        dev = &pcpu->dev;
 183        if (dev->id)
 184                device_remove_file(dev, &dev_attr_online);
 185
 186        /* pcpu remove would be implicitly done */
 187        device_unregister(dev);
 188}
 189
 190static int register_pcpu(struct pcpu *pcpu)
 191{
 192        struct device *dev;
 193        int err = -EINVAL;
 194
 195        if (!pcpu)
 196                return err;
 197
 198        dev = &pcpu->dev;
 199        dev->bus = &xen_pcpu_subsys;
 200        dev->id = pcpu->cpu_id;
 201        dev->release = pcpu_release;
 202
 203        err = device_register(dev);
 204        if (err) {
 205                pcpu_release(dev);
 206                return err;
 207        }
 208
 209        /*
 210         * Xen never offline cpu0 due to several restrictions
 211         * and assumptions. This basically doesn't add a sys control
 212         * to user, one cannot attempt to offline BSP.
 213         */
 214        if (dev->id) {
 215                err = device_create_file(dev, &dev_attr_online);
 216                if (err) {
 217                        device_unregister(dev);
 218                        return err;
 219                }
 220        }
 221
 222        return 0;
 223}
 224
 225static struct pcpu *create_and_register_pcpu(struct xenpf_pcpuinfo *info)
 226{
 227        struct pcpu *pcpu;
 228        int err;
 229
 230        if (info->flags & XEN_PCPU_FLAGS_INVALID)
 231                return ERR_PTR(-ENODEV);
 232
 233        pcpu = kzalloc(sizeof(struct pcpu), GFP_KERNEL);
 234        if (!pcpu)
 235                return ERR_PTR(-ENOMEM);
 236
 237        INIT_LIST_HEAD(&pcpu->list);
 238        pcpu->cpu_id = info->xen_cpuid;
 239        pcpu->flags = info->flags;
 240
 241        /* Need hold on xen_pcpu_lock before pcpu list manipulations */
 242        list_add_tail(&pcpu->list, &xen_pcpus);
 243
 244        err = register_pcpu(pcpu);
 245        if (err) {
 246                pr_warn("Failed to register pcpu%u\n", 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                unregister_and_remove_pcpu(pcpu);
 282                return 0;
 283        }
 284
 285        if (!pcpu) {
 286                pcpu = create_and_register_pcpu(info);
 287                if (IS_ERR_OR_NULL(pcpu))
 288                        return -ENODEV;
 289        } else
 290                pcpu_online_status(info, pcpu);
 291
 292        return 0;
 293}
 294
 295/*
 296 * Sync dom0's pcpu information with xen hypervisor's
 297 */
 298static int xen_sync_pcpus(void)
 299{
 300        /*
 301         * Boot cpu always have cpu_id 0 in xen
 302         */
 303        uint32_t cpu = 0, max_cpu = 0;
 304        int err = 0;
 305        struct pcpu *pcpu, *tmp;
 306
 307        mutex_lock(&xen_pcpu_lock);
 308
 309        while (!err && (cpu <= max_cpu)) {
 310                err = sync_pcpu(cpu, &max_cpu);
 311                cpu++;
 312        }
 313
 314        if (err)
 315                list_for_each_entry_safe(pcpu, tmp, &xen_pcpus, list)
 316                        unregister_and_remove_pcpu(pcpu);
 317
 318        mutex_unlock(&xen_pcpu_lock);
 319
 320        return err;
 321}
 322
 323static void xen_pcpu_work_fn(struct work_struct *work)
 324{
 325        xen_sync_pcpus();
 326}
 327static DECLARE_WORK(xen_pcpu_work, xen_pcpu_work_fn);
 328
 329static irqreturn_t xen_pcpu_interrupt(int irq, void *dev_id)
 330{
 331        schedule_work(&xen_pcpu_work);
 332        return IRQ_HANDLED;
 333}
 334
 335/* Sync with Xen hypervisor after cpu hotadded */
 336void xen_pcpu_hotplug_sync(void)
 337{
 338        schedule_work(&xen_pcpu_work);
 339}
 340EXPORT_SYMBOL_GPL(xen_pcpu_hotplug_sync);
 341
 342/*
 343 * For hypervisor presented cpu, return logic cpu id;
 344 * For hypervisor non-presented cpu, return -ENODEV.
 345 */
 346int xen_pcpu_id(uint32_t acpi_id)
 347{
 348        int cpu_id = 0, max_id = 0;
 349        struct xen_platform_op op;
 350
 351        op.cmd = XENPF_get_cpuinfo;
 352        while (cpu_id <= max_id) {
 353                op.u.pcpu_info.xen_cpuid = cpu_id;
 354                if (HYPERVISOR_dom0_op(&op)) {
 355                        cpu_id++;
 356                        continue;
 357                }
 358
 359                if (acpi_id == op.u.pcpu_info.acpi_id)
 360                        return cpu_id;
 361                if (op.u.pcpu_info.max_present > max_id)
 362                        max_id = op.u.pcpu_info.max_present;
 363                cpu_id++;
 364        }
 365
 366        return -ENODEV;
 367}
 368EXPORT_SYMBOL_GPL(xen_pcpu_id);
 369
 370static int __init xen_pcpu_init(void)
 371{
 372        int irq, ret;
 373
 374        if (!xen_initial_domain())
 375                return -ENODEV;
 376
 377        irq = bind_virq_to_irqhandler(VIRQ_PCPU_STATE, 0,
 378                                      xen_pcpu_interrupt, 0,
 379                                      "xen-pcpu", NULL);
 380        if (irq < 0) {
 381                pr_warn("Failed to bind pcpu virq\n");
 382                return irq;
 383        }
 384
 385        ret = subsys_system_register(&xen_pcpu_subsys, NULL);
 386        if (ret) {
 387                pr_warn("Failed to register pcpu subsys\n");
 388                goto err1;
 389        }
 390
 391        ret = xen_sync_pcpus();
 392        if (ret) {
 393                pr_warn("Failed to sync pcpu info\n");
 394                goto err2;
 395        }
 396
 397        return 0;
 398
 399err2:
 400        bus_unregister(&xen_pcpu_subsys);
 401err1:
 402        unbind_from_irqhandler(irq, NULL);
 403        return ret;
 404}
 405arch_initcall(xen_pcpu_init);
 406