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/******************************************************************************
 * 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 __poll_t xen_mce_chrdev_poll(struct file *file, poll_table *wait)
{
	poll_wait(file, &xen_mce_chrdev_wait, wait);

	if (xen_mcelog.next)
		return EPOLLIN | EPOLLRDNORM;

	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\n");
		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\n", 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\n");
		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;
	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\n",
			       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\n");

			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\n");
				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\n");

	/* nonurgent mc_info */
	err = mc_queue_handle(XEN_MC_NONURGENT);
	if (err)
		pr_err("Failed to handle nonurgent mc_info queue\n");

	/* 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;
	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\n");
		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\n");
		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\n");
		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;

	pr_info("/dev/mcelog registered by Xen\n");

	return 0;

deregister:
	misc_deregister(&xen_mce_chrdev_device);
	return ret;
}
device_initcall(xen_late_init_mcelog);