/******************************************************************************
 * pcpu.c
 * Management physical cpu in dom0, get pcpu info and provide sys interface
 *
 * Copyright (c) 2012 Intel Corporation
 * Author: Liu, Jinsong <jinsong.liu@intel.com>
 * Author: Jiang, Yunhong <yunhong.jiang@intel.com>
 *
 * 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.
 */

#define pr_fmt(fmt) "xen_cpu: " fmt

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


/*
 * @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_platform_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_platform_op(&op);
}

static ssize_t online_show(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 online_store(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_RW(online);

static struct attribute *pcpu_dev_attrs[] = {
        &dev_attr_online.attr,
        NULL
};

static umode_t pcpu_dev_is_visible(struct kobject *kobj,
                                   struct attribute *attr, int idx)
{
        struct device *dev = kobj_to_dev(kobj);
        /*
         * 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.
         */
        return dev->id ? attr->mode : 0;
}

static const struct attribute_group pcpu_dev_group = {
        .attrs = pcpu_dev_attrs,
        .is_visible = pcpu_dev_is_visible,
};

static const struct attribute_group *pcpu_dev_groups[] = {
        &pcpu_dev_group,
        NULL
};

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;
        /* 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;
        dev->groups = pcpu_dev_groups;

        err = device_register(dev);
        if (err) {
                pcpu_release(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_warn("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_platform_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) {
                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_warn("Failed to bind pcpu virq\n");
                return irq;
        }

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

        ret = xen_sync_pcpus();
        if (ret) {
                pr_warn("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);