/******************************************************************************
   * 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/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_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
  ", !!(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_warn("Failed to register pcpu%u
  ", 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) {
  		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;
  }
  
  /* Sync with Xen hypervisor after cpu hotadded */
  void xen_pcpu_hotplug_sync(void)
  {
  	schedule_work(&xen_pcpu_work);
  }
  EXPORT_SYMBOL_GPL(xen_pcpu_hotplug_sync);
  
  /*
   * For hypervisor presented cpu, return logic cpu id;
   * For hypervisor non-presented cpu, return -ENODEV.
   */
  int xen_pcpu_id(uint32_t acpi_id)
  {
  	int cpu_id = 0, max_id = 0;
  	struct xen_platform_op op;
  
  	op.cmd = XENPF_get_cpuinfo;
  	while (cpu_id <= max_id) {
  		op.u.pcpu_info.xen_cpuid = cpu_id;
  		if (HYPERVISOR_dom0_op(&op)) {
  			cpu_id++;
  			continue;
  		}
  
  		if (acpi_id == op.u.pcpu_info.acpi_id)
  			return cpu_id;
  		if (op.u.pcpu_info.max_present > max_id)
  			max_id = op.u.pcpu_info.max_present;
  		cpu_id++;
  	}
  
  	return -ENODEV;
  }
  EXPORT_SYMBOL_GPL(xen_pcpu_id);
  
  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
  ");
  		return irq;
  	}
  
  	ret = subsys_system_register(&xen_pcpu_subsys, NULL);
  	if (ret) {
  		pr_warn("Failed to register pcpu subsys
  ");
  		goto err1;
  	}
  
  	ret = xen_sync_pcpus();
  	if (ret) {
  		pr_warn("Failed to sync pcpu info
  ");
  		goto err2;
  	}
  
  	return 0;
  
  err2:
  	bus_unregister(&xen_pcpu_subsys);
  err1:
  	unbind_from_irqhandler(irq, NULL);
  	return ret;
  }
  arch_initcall(xen_pcpu_init);