/******************************************************************************
   * mcelog.c
   * Driver for receiving and transferring machine check error infomation
   *
   * Copyright (c) 2012 Intel Corporation
   * Author: Liu, Jinsong <jinsong.liu@intel.com>
   * Author: Jiang, Yunhong <yunhong.jiang@intel.com>
   * Author: Ke, Liping <liping.ke@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_mcelog: " fmt
  
  #include <linux/init.h>
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/slab.h>
  #include <linux/fs.h>
  #include <linux/device.h>
  #include <linux/miscdevice.h>
  #include <linux/uaccess.h>
  #include <linux/capability.h>
  #include <linux/poll.h>
  #include <linux/sched.h>
  
  #include <xen/interface/xen.h>
  #include <xen/events.h>
  #include <xen/interface/vcpu.h>
  #include <xen/xen.h>
  #include <asm/xen/hypercall.h>
  #include <asm/xen/hypervisor.h>
  
  static struct mc_info g_mi;
  static struct mcinfo_logical_cpu *g_physinfo;
  static uint32_t ncpus;
  
  static DEFINE_MUTEX(mcelog_lock);
  
  static struct xen_mce_log xen_mcelog = {
  	.signature	= XEN_MCE_LOG_SIGNATURE,
  	.len		= XEN_MCE_LOG_LEN,
  	.recordlen	= sizeof(struct xen_mce),
  };
  
  static DEFINE_SPINLOCK(xen_mce_chrdev_state_lock);
  static int xen_mce_chrdev_open_count;	/* #times opened */
  static int xen_mce_chrdev_open_exclu;	/* already open exclusive? */
  
  static DECLARE_WAIT_QUEUE_HEAD(xen_mce_chrdev_wait);
  
  static int xen_mce_chrdev_open(struct inode *inode, struct file *file)
  {
  	spin_lock(&xen_mce_chrdev_state_lock);
  
  	if (xen_mce_chrdev_open_exclu ||
  	    (xen_mce_chrdev_open_count && (file->f_flags & O_EXCL))) {
  		spin_unlock(&xen_mce_chrdev_state_lock);
  
  		return -EBUSY;
  	}
  
  	if (file->f_flags & O_EXCL)
  		xen_mce_chrdev_open_exclu = 1;
  	xen_mce_chrdev_open_count++;
  
  	spin_unlock(&xen_mce_chrdev_state_lock);
  
  	return nonseekable_open(inode, file);
  }
  
  static int xen_mce_chrdev_release(struct inode *inode, struct file *file)
  {
  	spin_lock(&xen_mce_chrdev_state_lock);
  
  	xen_mce_chrdev_open_count--;
  	xen_mce_chrdev_open_exclu = 0;
  
  	spin_unlock(&xen_mce_chrdev_state_lock);
  
  	return 0;
  }
  
  static ssize_t xen_mce_chrdev_read(struct file *filp, char __user *ubuf,
  				size_t usize, loff_t *off)
  {
  	char __user *buf = ubuf;
  	unsigned num;
  	int i, err;
  
  	mutex_lock(&mcelog_lock);
  
  	num = xen_mcelog.next;
  
  	/* Only supports full reads right now */
  	err = -EINVAL;
  	if (*off != 0 || usize < XEN_MCE_LOG_LEN*sizeof(struct xen_mce))
  		goto out;
  
  	err = 0;
  	for (i = 0; i < num; i++) {
  		struct xen_mce *m = &xen_mcelog.entry[i];
  
  		err |= copy_to_user(buf, m, sizeof(*m));
  		buf += sizeof(*m);
  	}
  
  	memset(xen_mcelog.entry, 0, num * sizeof(struct xen_mce));
  	xen_mcelog.next = 0;
  
  	if (err)
  		err = -EFAULT;
  
  out:
  	mutex_unlock(&mcelog_lock);
  
  	return err ? err : buf - ubuf;
  }
  
  static unsigned int xen_mce_chrdev_poll(struct file *file, poll_table *wait)
  {
  	poll_wait(file, &xen_mce_chrdev_wait, wait);
  
  	if (xen_mcelog.next)
  		return POLLIN | POLLRDNORM;
  
  	return 0;
  }
  
  static long xen_mce_chrdev_ioctl(struct file *f, unsigned int cmd,
  				unsigned long arg)
  {
  	int __user *p = (int __user *)arg;
  
  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;
  
  	switch (cmd) {
  	case MCE_GET_RECORD_LEN:
  		return put_user(sizeof(struct xen_mce), p);
  	case MCE_GET_LOG_LEN:
  		return put_user(XEN_MCE_LOG_LEN, p);
  	case MCE_GETCLEAR_FLAGS: {
  		unsigned flags;
  
  		do {
  			flags = xen_mcelog.flags;
  		} while (cmpxchg(&xen_mcelog.flags, flags, 0) != flags);
  
  		return put_user(flags, p);
  	}
  	default:
  		return -ENOTTY;
  	}
  }
  
  static const struct file_operations xen_mce_chrdev_ops = {
  	.open			= xen_mce_chrdev_open,
  	.release		= xen_mce_chrdev_release,
  	.read			= xen_mce_chrdev_read,
  	.poll			= xen_mce_chrdev_poll,
  	.unlocked_ioctl		= xen_mce_chrdev_ioctl,
  	.llseek			= no_llseek,
  };
  
  static struct miscdevice xen_mce_chrdev_device = {
  	MISC_MCELOG_MINOR,
  	"mcelog",
  	&xen_mce_chrdev_ops,
  };
  
  /*
   * Caller should hold the mcelog_lock
   */
  static void xen_mce_log(struct xen_mce *mce)
  {
  	unsigned entry;
  
  	entry = xen_mcelog.next;
  
  	/*
  	 * When the buffer fills up discard new entries.
  	 * Assume that the earlier errors are the more
  	 * interesting ones:
  	 */
  	if (entry >= XEN_MCE_LOG_LEN) {
  		set_bit(XEN_MCE_OVERFLOW,
  			(unsigned long *)&xen_mcelog.flags);
  		return;
  	}
  
  	memcpy(xen_mcelog.entry + entry, mce, sizeof(struct xen_mce));
  
  	xen_mcelog.next++;
  }
  
  static int convert_log(struct mc_info *mi)
  {
  	struct mcinfo_common *mic;
  	struct mcinfo_global *mc_global;
  	struct mcinfo_bank *mc_bank;
  	struct xen_mce m;
  	uint32_t i;
  
  	mic = NULL;
  	x86_mcinfo_lookup(&mic, mi, MC_TYPE_GLOBAL);
  	if (unlikely(!mic)) {
  		pr_warn("Failed to find global error info
  ");
  		return -ENODEV;
  	}
  
  	memset(&m, 0, sizeof(struct xen_mce));
  
  	mc_global = (struct mcinfo_global *)mic;
  	m.mcgstatus = mc_global->mc_gstatus;
  	m.apicid = mc_global->mc_apicid;
  
  	for (i = 0; i < ncpus; i++)
  		if (g_physinfo[i].mc_apicid == m.apicid)
  			break;
  	if (unlikely(i == ncpus)) {
  		pr_warn("Failed to match cpu with apicid %d
  ", m.apicid);
  		return -ENODEV;
  	}
  
  	m.socketid = g_physinfo[i].mc_chipid;
  	m.cpu = m.extcpu = g_physinfo[i].mc_cpunr;
  	m.cpuvendor = (__u8)g_physinfo[i].mc_vendor;
  	m.mcgcap = g_physinfo[i].mc_msrvalues[__MC_MSR_MCGCAP].value;
  
  	mic = NULL;
  	x86_mcinfo_lookup(&mic, mi, MC_TYPE_BANK);
  	if (unlikely(!mic)) {
  		pr_warn("Fail to find bank error info
  ");
  		return -ENODEV;
  	}
  
  	do {
  		if ((!mic) || (mic->size == 0) ||
  		    (mic->type != MC_TYPE_GLOBAL   &&
  		     mic->type != MC_TYPE_BANK     &&
  		     mic->type != MC_TYPE_EXTENDED &&
  		     mic->type != MC_TYPE_RECOVERY))
  			break;
  
  		if (mic->type == MC_TYPE_BANK) {
  			mc_bank = (struct mcinfo_bank *)mic;
  			m.misc = mc_bank->mc_misc;
  			m.status = mc_bank->mc_status;
  			m.addr = mc_bank->mc_addr;
  			m.tsc = mc_bank->mc_tsc;
  			m.bank = mc_bank->mc_bank;
  			m.finished = 1;
  			/*log this record*/
  			xen_mce_log(&m);
  		}
  		mic = x86_mcinfo_next(mic);
  	} while (1);
  
  	return 0;
  }
  
  static int mc_queue_handle(uint32_t flags)
  {
  	struct xen_mc mc_op;
  	int ret = 0;
  
  	mc_op.cmd = XEN_MC_fetch;
  	mc_op.interface_version = XEN_MCA_INTERFACE_VERSION;
  	set_xen_guest_handle(mc_op.u.mc_fetch.data, &g_mi);
  	do {
  		mc_op.u.mc_fetch.flags = flags;
  		ret = HYPERVISOR_mca(&mc_op);
  		if (ret) {
  			pr_err("Failed to fetch %surgent error log
  ",
  			       flags == XEN_MC_URGENT ? "" : "non");
  			break;
  		}
  
  		if (mc_op.u.mc_fetch.flags & XEN_MC_NODATA ||
  		    mc_op.u.mc_fetch.flags & XEN_MC_FETCHFAILED)
  			break;
  		else {
  			ret = convert_log(&g_mi);
  			if (ret)
  				pr_warn("Failed to convert this error log, continue acking it anyway
  ");
  
  			mc_op.u.mc_fetch.flags = flags | XEN_MC_ACK;
  			ret = HYPERVISOR_mca(&mc_op);
  			if (ret) {
  				pr_err("Failed to ack previous error log
  ");
  				break;
  			}
  		}
  	} while (1);
  
  	return ret;
  }
  
  /* virq handler for machine check error info*/
  static void xen_mce_work_fn(struct work_struct *work)
  {
  	int err;
  
  	mutex_lock(&mcelog_lock);
  
  	/* urgent mc_info */
  	err = mc_queue_handle(XEN_MC_URGENT);
  	if (err)
  		pr_err("Failed to handle urgent mc_info queue, continue handling nonurgent mc_info queue anyway
  ");
  
  	/* nonurgent mc_info */
  	err = mc_queue_handle(XEN_MC_NONURGENT);
  	if (err)
  		pr_err("Failed to handle nonurgent mc_info queue
  ");
  
  	/* wake processes polling /dev/mcelog */
  	wake_up_interruptible(&xen_mce_chrdev_wait);
  
  	mutex_unlock(&mcelog_lock);
  }
  static DECLARE_WORK(xen_mce_work, xen_mce_work_fn);
  
  static irqreturn_t xen_mce_interrupt(int irq, void *dev_id)
  {
  	schedule_work(&xen_mce_work);
  	return IRQ_HANDLED;
  }
  
  static int bind_virq_for_mce(void)
  {
  	int ret;
  	struct xen_mc mc_op;
  
  	memset(&mc_op, 0, sizeof(struct xen_mc));
  
  	/* Fetch physical CPU Numbers */
  	mc_op.cmd = XEN_MC_physcpuinfo;
  	mc_op.interface_version = XEN_MCA_INTERFACE_VERSION;
  	set_xen_guest_handle(mc_op.u.mc_physcpuinfo.info, g_physinfo);
  	ret = HYPERVISOR_mca(&mc_op);
  	if (ret) {
  		pr_err("Failed to get CPU numbers
  ");
  		return ret;
  	}
  
  	/* Fetch each CPU Physical Info for later reference*/
  	ncpus = mc_op.u.mc_physcpuinfo.ncpus;
  	g_physinfo = kcalloc(ncpus, sizeof(struct mcinfo_logical_cpu),
  			     GFP_KERNEL);
  	if (!g_physinfo)
  		return -ENOMEM;
  	set_xen_guest_handle(mc_op.u.mc_physcpuinfo.info, g_physinfo);
  	ret = HYPERVISOR_mca(&mc_op);
  	if (ret) {
  		pr_err("Failed to get CPU info
  ");
  		kfree(g_physinfo);
  		return ret;
  	}
  
  	ret  = bind_virq_to_irqhandler(VIRQ_MCA, 0,
  				       xen_mce_interrupt, 0, "mce", NULL);
  	if (ret < 0) {
  		pr_err("Failed to bind virq
  ");
  		kfree(g_physinfo);
  		return ret;
  	}
  
  	return 0;
  }
  
  static int __init xen_late_init_mcelog(void)
  {
  	int ret;
  
  	/* Only DOM0 is responsible for MCE logging */
  	if (!xen_initial_domain())
  		return -ENODEV;
  
  	/* register character device /dev/mcelog for xen mcelog */
  	ret = misc_register(&xen_mce_chrdev_device);
  	if (ret)
  		return ret;
  
  	ret = bind_virq_for_mce();
  	if (ret)
  		goto deregister;
  
  	return 0;
  
  deregister:
  	misc_deregister(&xen_mce_chrdev_device);
  	return ret;
  }
  device_initcall(xen_late_init_mcelog);