pcpu.c

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/******************************************************************************
 * pcpu.c
 * Management physical cpu in dom0, get pcpu info and provide sys interface
 *
 * Copyright (c) 2012 Intel Corporation
 * Author: Liu, Jinsong <[email protected]>
 * Author: Jiang, Yunhong <[email protected]>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/cpu.h>
#include <linux/stat.h>
#include <linux/capability.h>

#include <xen/xen.h>
#include <xen/xenbus.h>
#include <xen/events.h>
#include <xen/interface/platform.h>
#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>

#define XEN_PCPU "xen_cpu: "

/*
 * @cpu_id: Xen physical cpu logic number
 * @flags: Xen physical cpu status flag
 * - XEN_PCPU_FLAGS_ONLINE: cpu is online
 * - XEN_PCPU_FLAGS_INVALID: cpu is not present
 */
struct pcpu {
    struct list_head list;
    struct device dev;
    uint32_t cpu_id;
    uint32_t flags;
};

static struct bus_type xen_pcpu_subsys = {
    .name = "xen_cpu",
    .dev_name = "xen_cpu",
};

static DEFINE_MUTEX(xen_pcpu_lock);

static LIST_HEAD(xen_pcpus);

static int xen_pcpu_down(uint32_t cpu_id)
{
    struct xen_platform_op op = {
        .cmd            = XENPF_cpu_offline,
        .interface_version  = XENPF_INTERFACE_VERSION,
        .u.cpu_ol.cpuid     = cpu_id,
    };

    return HYPERVISOR_dom0_op(&op);
}

static int xen_pcpu_up(uint32_t cpu_id)
{
    struct xen_platform_op op = {
        .cmd            = XENPF_cpu_online,
        .interface_version  = XENPF_INTERFACE_VERSION,
        .u.cpu_ol.cpuid     = cpu_id,
    };

    return HYPERVISOR_dom0_op(&op);
}

static ssize_t show_online(struct device *dev,
               struct device_attribute *attr,
               char *buf)
{
    struct pcpu *cpu = container_of(dev, struct pcpu, dev);

    return sprintf(buf, "%u\n", !!(cpu->flags & XEN_PCPU_FLAGS_ONLINE));
}

static ssize_t __ref store_online(struct device *dev,
                  struct device_attribute *attr,
                  const char *buf, size_t count)
{
    struct pcpu *pcpu = container_of(dev, struct pcpu, dev);
    unsigned long long val;
    ssize_t ret;

    if (!capable(CAP_SYS_ADMIN))
        return -EPERM;

    if (kstrtoull(buf, 0, &val) < 0)
        return -EINVAL;

    switch (val) {
    case 0:
        ret = xen_pcpu_down(pcpu->cpu_id);
        break;
    case 1:
        ret = xen_pcpu_up(pcpu->cpu_id);
        break;
    default:
        ret = -EINVAL;
    }

    if (ret >= 0)
        ret = count;
    return ret;
}
static DEVICE_ATTR(online, S_IRUGO | S_IWUSR, show_online, store_online);

static bool xen_pcpu_online(uint32_t flags)
{
    return !!(flags & XEN_PCPU_FLAGS_ONLINE);
}

static void pcpu_online_status(struct xenpf_pcpuinfo *info,
                   struct pcpu *pcpu)
{
    if (xen_pcpu_online(info->flags) &&
       !xen_pcpu_online(pcpu->flags)) {
        /* the pcpu is onlined */
        pcpu->flags |= XEN_PCPU_FLAGS_ONLINE;
        kobject_uevent(&pcpu->dev.kobj, KOBJ_ONLINE);
    } else if (!xen_pcpu_online(info->flags) &&
            xen_pcpu_online(pcpu->flags)) {
        /* The pcpu is offlined */
        pcpu->flags &= ~XEN_PCPU_FLAGS_ONLINE;
        kobject_uevent(&pcpu->dev.kobj, KOBJ_OFFLINE);
    }
}

static struct pcpu *get_pcpu(uint32_t cpu_id)
{
    struct pcpu *pcpu;

    list_for_each_entry(pcpu, &xen_pcpus, list) {
        if (pcpu->cpu_id == cpu_id)
            return pcpu;
    }

    return NULL;
}

static void pcpu_release(struct device *dev)
{
    struct pcpu *pcpu = container_of(dev, struct pcpu, dev);

    list_del(&pcpu->list);
    kfree(pcpu);
}

static void unregister_and_remove_pcpu(struct pcpu *pcpu)
{
    struct device *dev;

    if (!pcpu)
        return;

    dev = &pcpu->dev;
    if (dev->id)
        device_remove_file(dev, &dev_attr_online);

    /* pcpu remove would be implicitly done */
    device_unregister(dev);
}

static int register_pcpu(struct pcpu *pcpu)
{
    struct device *dev;
    int err = -EINVAL;

    if (!pcpu)
        return err;

    dev = &pcpu->dev;
    dev->bus = &xen_pcpu_subsys;
    dev->id = pcpu->cpu_id;
    dev->release = pcpu_release;

    err = device_register(dev);
    if (err) {
        pcpu_release(dev);
        return err;
    }

    /*
     * Xen never offline cpu0 due to several restrictions
     * and assumptions. This basically doesn't add a sys control
     * to user, one cannot attempt to offline BSP.
     */
    if (dev->id) {
        err = device_create_file(dev, &dev_attr_online);
        if (err) {
            device_unregister(dev);
            return err;
        }
    }

    return 0;
}

static struct pcpu *create_and_register_pcpu(struct xenpf_pcpuinfo *info)
{
    struct pcpu *pcpu;
    int err;

    if (info->flags & XEN_PCPU_FLAGS_INVALID)
        return ERR_PTR(-ENODEV);

    pcpu = kzalloc(sizeof(struct pcpu), GFP_KERNEL);
    if (!pcpu)
        return ERR_PTR(-ENOMEM);

    INIT_LIST_HEAD(&pcpu->list);
    pcpu->cpu_id = info->xen_cpuid;
    pcpu->flags = info->flags;

    /* Need hold on xen_pcpu_lock before pcpu list manipulations */
    list_add_tail(&pcpu->list, &xen_pcpus);

    err = register_pcpu(pcpu);
    if (err) {
        pr_warning(XEN_PCPU "Failed to register pcpu%u\n",
               info->xen_cpuid);
        return ERR_PTR(-ENOENT);
    }

    return pcpu;
}

/*
 * Caller should hold the xen_pcpu_lock
 */
static int sync_pcpu(uint32_t cpu, uint32_t *max_cpu)
{
    int ret;
    struct pcpu *pcpu = NULL;
    struct xenpf_pcpuinfo *info;
    struct xen_platform_op op = {
        .cmd                   = XENPF_get_cpuinfo,
        .interface_version     = XENPF_INTERFACE_VERSION,
        .u.pcpu_info.xen_cpuid = cpu,
    };

    ret = HYPERVISOR_dom0_op(&op);
    if (ret)
        return ret;

    info = &op.u.pcpu_info;
    if (max_cpu)
        *max_cpu = info->max_present;

    pcpu = get_pcpu(cpu);

    /*
     * Only those at cpu present map has its sys interface.
     */
    if (info->flags & XEN_PCPU_FLAGS_INVALID) {
        if (pcpu)
            unregister_and_remove_pcpu(pcpu);
        return 0;
    }

    if (!pcpu) {
        pcpu = create_and_register_pcpu(info);
        if (IS_ERR_OR_NULL(pcpu))
            return -ENODEV;
    } else
        pcpu_online_status(info, pcpu);

    return 0;
}

/*
 * Sync dom0's pcpu information with xen hypervisor's
 */
static int xen_sync_pcpus(void)
{
    /*
     * Boot cpu always have cpu_id 0 in xen
     */
    uint32_t cpu = 0, max_cpu = 0;
    int err = 0;
    struct pcpu *pcpu, *tmp;

    mutex_lock(&xen_pcpu_lock);

    while (!err && (cpu <= max_cpu)) {
        err = sync_pcpu(cpu, &max_cpu);
        cpu++;
    }

    if (err)
        list_for_each_entry_safe(pcpu, tmp, &xen_pcpus, list)
            unregister_and_remove_pcpu(pcpu);

    mutex_unlock(&xen_pcpu_lock);

    return err;
}

static void xen_pcpu_work_fn(struct work_struct *work)
{
    xen_sync_pcpus();
}
static DECLARE_WORK(xen_pcpu_work, xen_pcpu_work_fn);

static irqreturn_t xen_pcpu_interrupt(int irq, void *dev_id)
{
    schedule_work(&xen_pcpu_work);
    return IRQ_HANDLED;
}

static int __init xen_pcpu_init(void)
{
    int irq, ret;

    if (!xen_initial_domain())
        return -ENODEV;

    irq = bind_virq_to_irqhandler(VIRQ_PCPU_STATE, 0,
                      xen_pcpu_interrupt, 0,
                      "xen-pcpu", NULL);
    if (irq < 0) {
        pr_warning(XEN_PCPU "Failed to bind pcpu virq\n");
        return irq;
    }

    ret = subsys_system_register(&xen_pcpu_subsys, NULL);
    if (ret) {
        pr_warning(XEN_PCPU "Failed to register pcpu subsys\n");
        goto err1;
    }

    ret = xen_sync_pcpus();
    if (ret) {
        pr_warning(XEN_PCPU "Failed to sync pcpu info\n");
        goto err2;
    }

    return 0;

err2:
    bus_unregister(&xen_pcpu_subsys);
err1:
    unbind_from_irqhandler(irq, NULL);
    return ret;
}
arch_initcall(xen_pcpu_init);