drivers/tty/hvc/hvc_xen.c - kernel/msm-4.9 - Gitiles

 /*
  * xen console driver interface to hvc_console.c
  *
  * (c) 2007 Gerd Hoffmann <kraxel@suse.de>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  */

 #include <linux/console.h>
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/irq.h>
 #include <linux/init.h>
 #include <linux/types.h>
 #include <linux/list.h>

 #include <asm/io.h>
 #include <asm/xen/hypervisor.h>

 #include <xen/xen.h>
 #include <xen/interface/xen.h>
 #include <xen/hvm.h>
 #include <xen/grant_table.h>
 #include <xen/page.h>
 #include <xen/events.h>
 #include <xen/interface/io/console.h>
 #include <xen/interface/sched.h>
 #include <xen/hvc-console.h>
 #include <xen/xenbus.h>

 #include "hvc_console.h"

 #define HVC_COOKIE   0x58656e /* "Xen" in hex */

 struct xencons_info {
 	struct list_head list;
 	struct xenbus_device *xbdev;
 	struct xencons_interface *intf;
 	unsigned int evtchn;
 	struct hvc_struct *hvc;
 	int irq;
 	int vtermno;
 	grant_ref_t gntref;
 };

 static LIST_HEAD(xenconsoles);
 static DEFINE_SPINLOCK(xencons_lock);

 /* ------------------------------------------------------------------ */

 static struct xencons_info *vtermno_to_xencons(int vtermno)
 {
 	struct xencons_info *entry, *n, *ret = NULL;

 	if (list_empty(&xenconsoles))
 			return NULL;

 	list_for_each_entry_safe(entry, n, &xenconsoles, list) {
 		if (entry->vtermno == vtermno) {
 			ret  = entry;
 			break;
 		}
 	}

 	return ret;
 }

 static inline int xenbus_devid_to_vtermno(int devid)
 {
 	return devid + HVC_COOKIE;
 }

 static inline void notify_daemon(struct xencons_info *cons)
 {
 	/* Use evtchn: this is called early, before irq is set up. */
 	notify_remote_via_evtchn(cons->evtchn);
 }

 static int __write_console(struct xencons_info *xencons,
 		const char *data, int len)
 {
 	XENCONS_RING_IDX cons, prod;
 	struct xencons_interface *intf = xencons->intf;
 	int sent = 0;

 	cons = intf->out_cons;
 	prod = intf->out_prod;
 	mb();			/* update queue values before going on */
 	BUG_ON((prod - cons) > sizeof(intf->out));

 	while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
 		intf->out[MASK_XENCONS_IDX(prod++, intf->out)] = data[sent++];

 	wmb();			/* write ring before updating pointer */
 	intf->out_prod = prod;

 	if (sent)
 		notify_daemon(xencons);
 	return sent;
 }

 static int domU_write_console(uint32_t vtermno, const char *data, int len)
 {
 	int ret = len;
 	struct xencons_info *cons = vtermno_to_xencons(vtermno);
 	if (cons == NULL)
 		return -EINVAL;

 	/*
 	 * Make sure the whole buffer is emitted, polling if
 	 * necessary.  We don't ever want to rely on the hvc daemon
 	 * because the most interesting console output is when the
 	 * kernel is crippled.
 	 */
 	while (len) {
 		int sent = __write_console(cons, data, len);

 		data += sent;
 		len -= sent;

 		if (unlikely(len))
 			HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 	}

 	return ret;
 }

 static int domU_read_console(uint32_t vtermno, char *buf, int len)
 {
 	struct xencons_interface *intf;
 	XENCONS_RING_IDX cons, prod;
 	int recv = 0;
 	struct xencons_info *xencons = vtermno_to_xencons(vtermno);
 	if (xencons == NULL)
 		return -EINVAL;
 	intf = xencons->intf;

 	cons = intf->in_cons;
 	prod = intf->in_prod;
 	mb();			/* get pointers before reading ring */
 	BUG_ON((prod - cons) > sizeof(intf->in));

 	while (cons != prod && recv < len)
 		buf[recv++] = intf->in[MASK_XENCONS_IDX(cons++, intf->in)];

 	mb();			/* read ring before consuming */
 	intf->in_cons = cons;

 	notify_daemon(xencons);
 	return recv;
 }

 static struct hv_ops domU_hvc_ops = {
 	.get_chars = domU_read_console,
 	.put_chars = domU_write_console,
 	.notifier_add = notifier_add_irq,
 	.notifier_del = notifier_del_irq,
 	.notifier_hangup = notifier_hangup_irq,
 };

 static int dom0_read_console(uint32_t vtermno, char *buf, int len)
 {
 	return HYPERVISOR_console_io(CONSOLEIO_read, len, buf);
 }

 /*
  * Either for a dom0 to write to the system console, or a domU with a
  * debug version of Xen
  */
 static int dom0_write_console(uint32_t vtermno, const char *str, int len)
 {
 	int rc = HYPERVISOR_console_io(CONSOLEIO_write, len, (char *)str);
 	if (rc < 0)
 		return 0;

 	return len;
 }

 static struct hv_ops dom0_hvc_ops = {
 	.get_chars = dom0_read_console,
 	.put_chars = dom0_write_console,
 	.notifier_add = notifier_add_irq,
 	.notifier_del = notifier_del_irq,
 	.notifier_hangup = notifier_hangup_irq,
 };

 static int xen_hvm_console_init(void)
 {
 	int r;
 	uint64_t v = 0;
 	unsigned long mfn;
 	struct xencons_info *info;

 	if (!xen_hvm_domain())
 		return -ENODEV;

 	info = vtermno_to_xencons(HVC_COOKIE);
 	if (!info) {
 		info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
 		if (!info)
 			return -ENOMEM;
 	} else if (info->intf != NULL) {
 		/* already configured */
 		return 0;
 	}
 	/*
 	 * If the toolstack (or the hypervisor) hasn't set these values, the
 	 * default value is 0. Even though mfn = 0 and evtchn = 0 are
 	 * theoretically correct values, in practice they never are and they
 	 * mean that a legacy toolstack hasn't initialized the pv console correctly.
 	 */
 	r = hvm_get_parameter(HVM_PARAM_CONSOLE_EVTCHN, &v);
 	if (r < 0 || v == 0)
 		goto err;
 	info->evtchn = v;
 	v = 0;
 	r = hvm_get_parameter(HVM_PARAM_CONSOLE_PFN, &v);
 	if (r < 0 || v == 0)
 		goto err;
 	mfn = v;
 	info->intf = xen_remap(mfn << PAGE_SHIFT, PAGE_SIZE);
 	if (info->intf == NULL)
 		goto err;
 	info->vtermno = HVC_COOKIE;

 	spin_lock(&xencons_lock);
 	list_add_tail(&info->list, &xenconsoles);
 	spin_unlock(&xencons_lock);

 	return 0;
 err:
 	kfree(info);
 	return -ENODEV;
 }

 static int xen_pv_console_init(void)
 {
 	struct xencons_info *info;

 	if (!xen_pv_domain())
 		return -ENODEV;

 	if (!xen_start_info->console.domU.evtchn)
 		return -ENODEV;

 	info = vtermno_to_xencons(HVC_COOKIE);
 	if (!info) {
 		info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
 		if (!info)
 			return -ENOMEM;
 	} else if (info->intf != NULL) {
 		/* already configured */
 		return 0;
 	}
 	info->evtchn = xen_start_info->console.domU.evtchn;
 	info->intf = mfn_to_virt(xen_start_info->console.domU.mfn);
 	info->vtermno = HVC_COOKIE;

 	spin_lock(&xencons_lock);
 	list_add_tail(&info->list, &xenconsoles);
 	spin_unlock(&xencons_lock);

 	return 0;
 }

 static int xen_initial_domain_console_init(void)
 {
 	struct xencons_info *info;

 	if (!xen_initial_domain())
 		return -ENODEV;

 	info = vtermno_to_xencons(HVC_COOKIE);
 	if (!info) {
 		info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
 		if (!info)
 			return -ENOMEM;
 	}

 	info->irq = bind_virq_to_irq(VIRQ_CONSOLE, 0);
 	info->vtermno = HVC_COOKIE;

 	spin_lock(&xencons_lock);
 	list_add_tail(&info->list, &xenconsoles);
 	spin_unlock(&xencons_lock);

 	return 0;
 }

 void xen_console_resume(void)
 {
 	struct xencons_info *info = vtermno_to_xencons(HVC_COOKIE);
 	if (info != NULL && info->irq)
 		rebind_evtchn_irq(info->evtchn, info->irq);
 }

 static void xencons_disconnect_backend(struct xencons_info *info)
 {
 	if (info->irq > 0)
 		unbind_from_irqhandler(info->irq, NULL);
 	info->irq = 0;
 	if (info->evtchn > 0)
 		xenbus_free_evtchn(info->xbdev, info->evtchn);
 	info->evtchn = 0;
 	if (info->gntref > 0)
 		gnttab_free_grant_references(info->gntref);
 	info->gntref = 0;
 	if (info->hvc != NULL)
 		hvc_remove(info->hvc);
 	info->hvc = NULL;
 }

 static void xencons_free(struct xencons_info *info)
 {
 	free_page((unsigned long)info->intf);
 	info->intf = NULL;
 	info->vtermno = 0;
 	kfree(info);
 }

 static int xen_console_remove(struct xencons_info *info)
 {
 	xencons_disconnect_backend(info);
 	spin_lock(&xencons_lock);
 	list_del(&info->list);
 	spin_unlock(&xencons_lock);
 	if (info->xbdev != NULL)
 		xencons_free(info);
 	else {
 		if (xen_hvm_domain())
 			iounmap(info->intf);
 		kfree(info);
 	}
 	return 0;
 }

 #ifdef CONFIG_HVC_XEN_FRONTEND
 static struct xenbus_driver xencons_driver;

 static int xencons_remove(struct xenbus_device *dev)
 {
 	return xen_console_remove(dev_get_drvdata(&dev->dev));
 }

 static int xencons_connect_backend(struct xenbus_device *dev,
 				  struct xencons_info *info)
 {
 	int ret, evtchn, devid, ref, irq;
 	struct xenbus_transaction xbt;
 	grant_ref_t gref_head;
 	unsigned long mfn;

 	ret = xenbus_alloc_evtchn(dev, &evtchn);
 	if (ret)
 		return ret;
 	info->evtchn = evtchn;
 	irq = bind_evtchn_to_irq(evtchn);
 	if (irq < 0)
 		return irq;
 	info->irq = irq;
 	devid = dev->nodename[strlen(dev->nodename) - 1] - '0';
 	info->hvc = hvc_alloc(xenbus_devid_to_vtermno(devid),
 			irq, &domU_hvc_ops, 256);
 	if (IS_ERR(info->hvc))
 		return PTR_ERR(info->hvc);
 	if (xen_pv_domain())
 		mfn = virt_to_mfn(info->intf);
 	else
 		mfn = __pa(info->intf) >> PAGE_SHIFT;
 	ret = gnttab_alloc_grant_references(1, &gref_head);
 	if (ret < 0)
 		return ret;
 	info->gntref = gref_head;
 	ref = gnttab_claim_grant_reference(&gref_head);
 	if (ref < 0)
 		return ref;
 	gnttab_grant_foreign_access_ref(ref, info->xbdev->otherend_id,
 			mfn, 0);

  again:
 	ret = xenbus_transaction_start(&xbt);
 	if (ret) {
 		xenbus_dev_fatal(dev, ret, "starting transaction");
 		return ret;
 	}
 	ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", ref);
 	if (ret)
 		goto error_xenbus;
 	ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
 			    evtchn);
 	if (ret)
 		goto error_xenbus;
 	ret = xenbus_printf(xbt, dev->nodename, "type", "ioemu");
 	if (ret)
 		goto error_xenbus;
 	ret = xenbus_transaction_end(xbt, 0);
 	if (ret) {
 		if (ret == -EAGAIN)
 			goto again;
 		xenbus_dev_fatal(dev, ret, "completing transaction");
 		return ret;
 	}

 	xenbus_switch_state(dev, XenbusStateInitialised);
 	return 0;

  error_xenbus:
 	xenbus_transaction_end(xbt, 1);
 	xenbus_dev_fatal(dev, ret, "writing xenstore");
 	return ret;
 }

 static int xencons_probe(struct xenbus_device *dev,
 				  const struct xenbus_device_id *id)
 {
 	int ret, devid;
 	struct xencons_info *info;

 	devid = dev->nodename[strlen(dev->nodename) - 1] - '0';
 	if (devid == 0)
 		return -ENODEV;

 	info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
 	if (!info)
 		return -ENOMEM;
 	dev_set_drvdata(&dev->dev, info);
 	info->xbdev = dev;
 	info->vtermno = xenbus_devid_to_vtermno(devid);
 	info->intf = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
 	if (!info->intf)
 		goto error_nomem;

 	ret = xencons_connect_backend(dev, info);
 	if (ret < 0)
 		goto error;
 	spin_lock(&xencons_lock);
 	list_add_tail(&info->list, &xenconsoles);
 	spin_unlock(&xencons_lock);

 	return 0;

  error_nomem:
 	ret = -ENOMEM;
 	xenbus_dev_fatal(dev, ret, "allocating device memory");
  error:
 	xencons_disconnect_backend(info);
 	xencons_free(info);
 	return ret;
 }

 static int xencons_resume(struct xenbus_device *dev)
 {
 	struct xencons_info *info = dev_get_drvdata(&dev->dev);

 	xencons_disconnect_backend(info);
 	memset(info->intf, 0, PAGE_SIZE);
 	return xencons_connect_backend(dev, info);
 }

 static void xencons_backend_changed(struct xenbus_device *dev,
 				   enum xenbus_state backend_state)
 {
 	switch (backend_state) {
 	case XenbusStateReconfiguring:
 	case XenbusStateReconfigured:
 	case XenbusStateInitialising:
 	case XenbusStateInitialised:
 	case XenbusStateUnknown:
 		break;

 	case XenbusStateInitWait:
 		break;

 	case XenbusStateConnected:
 		xenbus_switch_state(dev, XenbusStateConnected);
 		break;

 	case XenbusStateClosed:
 		if (dev->state == XenbusStateClosed)
 			break;
 		/* Missed the backend's CLOSING state -- fallthrough */
 	case XenbusStateClosing:
 		xenbus_frontend_closed(dev);
 		break;
 	}
 }

 static const struct xenbus_device_id xencons_ids[] = {
 	{ "console" },
 	{ "" }
 };


 static DEFINE_XENBUS_DRIVER(xencons, "xenconsole",
 	.probe = xencons_probe,
 	.remove = xencons_remove,
 	.resume = xencons_resume,
 	.otherend_changed = xencons_backend_changed,
 );
 #endif /* CONFIG_HVC_XEN_FRONTEND */

 static int __init xen_hvc_init(void)
 {
 	int r;
 	struct xencons_info *info;
 	const struct hv_ops *ops;

 	if (!xen_domain())
 		return -ENODEV;

 	if (xen_initial_domain()) {
 		ops = &dom0_hvc_ops;
 		r = xen_initial_domain_console_init();
 		if (r < 0)
 			return r;
 		info = vtermno_to_xencons(HVC_COOKIE);
 	} else {
 		ops = &domU_hvc_ops;
 		if (xen_hvm_domain())
 			r = xen_hvm_console_init();
 		else
 			r = xen_pv_console_init();
 		if (r < 0)
 			return r;

 		info = vtermno_to_xencons(HVC_COOKIE);
 		info->irq = bind_evtchn_to_irq(info->evtchn);
 	}
 	if (info->irq < 0)
 		info->irq = 0; /* NO_IRQ */
 	else
 		irq_set_noprobe(info->irq);

 	info->hvc = hvc_alloc(HVC_COOKIE, info->irq, ops, 256);
 	if (IS_ERR(info->hvc)) {
 		r = PTR_ERR(info->hvc);
 		spin_lock(&xencons_lock);
 		list_del(&info->list);
 		spin_unlock(&xencons_lock);
 		if (info->irq)
 			unbind_from_irqhandler(info->irq, NULL);
 		kfree(info);
 		return r;
 	}

 	r = 0;
 #ifdef CONFIG_HVC_XEN_FRONTEND
 	r = xenbus_register_frontend(&xencons_driver);
 #endif
 	return r;
 }

 static void __exit xen_hvc_fini(void)
 {
 	struct xencons_info *entry, *next;

 	if (list_empty(&xenconsoles))
 			return;

 	list_for_each_entry_safe(entry, next, &xenconsoles, list) {
 		xen_console_remove(entry);
 	}
 }

 static int xen_cons_init(void)
 {
 	const struct hv_ops *ops;

 	if (!xen_domain())
 		return 0;

 	if (xen_initial_domain())
 		ops = &dom0_hvc_ops;
 	else {
 		int r;
 		ops = &domU_hvc_ops;

 		if (xen_hvm_domain())
 			r = xen_hvm_console_init();
 		else
 			r = xen_pv_console_init();
 		if (r < 0)
 			return r;
 	}

 	hvc_instantiate(HVC_COOKIE, 0, ops);
 	return 0;
 }


 module_init(xen_hvc_init);
 module_exit(xen_hvc_fini);
 console_initcall(xen_cons_init);

 #ifdef CONFIG_EARLY_PRINTK
 static void xenboot_write_console(struct console *console, const char *string,
 				  unsigned len)
 {
 	unsigned int linelen, off = 0;
 	const char *pos;

 	if (!xen_pv_domain())
 		return;

 	dom0_write_console(0, string, len);

 	if (xen_initial_domain())
 		return;

 	domU_write_console(0, "(early) ", 8);
 	while (off < len && NULL != (pos = strchr(string+off, '\n'))) {
 		linelen = pos-string+off;
 		if (off + linelen > len)
 			break;
 		domU_write_console(0, string+off, linelen);
 		domU_write_console(0, "\r\n", 2);
 		off += linelen + 1;
 	}
 	if (off < len)
 		domU_write_console(0, string+off, len-off);
 }

 struct console xenboot_console = {
 	.name		= "xenboot",
 	.write		= xenboot_write_console,
 	.flags		= CON_PRINTBUFFER | CON_BOOT | CON_ANYTIME,
 	.index		= -1,
 };
 #endif	/* CONFIG_EARLY_PRINTK */

 void xen_raw_console_write(const char *str)
 {
 	dom0_write_console(0, str, strlen(str));
 }

 void xen_raw_printk(const char *fmt, ...)
 {
 	static char buf[512];
 	va_list ap;

 	va_start(ap, fmt);
 	vsnprintf(buf, sizeof(buf), fmt, ap);
 	va_end(ap);

 	xen_raw_console_write(buf);
 }
	/*
	* xen console driver interface to hvc_console.c
	*
	* (c) 2007 Gerd Hoffmann <kraxel@suse.de>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	*/

	#include <linux/console.h>
	#include <linux/delay.h>
	#include <linux/err.h>
	#include <linux/irq.h>
	#include <linux/init.h>
	#include <linux/types.h>
	#include <linux/list.h>

	#include <asm/io.h>
	#include <asm/xen/hypervisor.h>

	#include <xen/xen.h>
	#include <xen/interface/xen.h>
	#include <xen/hvm.h>
	#include <xen/grant_table.h>
	#include <xen/page.h>
	#include <xen/events.h>
	#include <xen/interface/io/console.h>
	#include <xen/interface/sched.h>
	#include <xen/hvc-console.h>
	#include <xen/xenbus.h>

	#include "hvc_console.h"

	#define HVC_COOKIE 0x58656e /* "Xen" in hex */

	struct xencons_info {
	struct list_head list;
	struct xenbus_device *xbdev;
	struct xencons_interface *intf;
	unsigned int evtchn;
	struct hvc_struct *hvc;
	int irq;
	int vtermno;
	grant_ref_t gntref;
	};

	static LIST_HEAD(xenconsoles);
	static DEFINE_SPINLOCK(xencons_lock);

	/* ------------------------------------------------------------------ */

	static struct xencons_info *vtermno_to_xencons(int vtermno)
	{
	struct xencons_info entry, n, *ret = NULL;

	if (list_empty(&xenconsoles))
	return NULL;

	list_for_each_entry_safe(entry, n, &xenconsoles, list) {
	if (entry->vtermno == vtermno) {
	ret = entry;
	break;
	}
	}

	return ret;
	}

	static inline int xenbus_devid_to_vtermno(int devid)
	{
	return devid + HVC_COOKIE;
	}

	static inline void notify_daemon(struct xencons_info *cons)
	{
	/* Use evtchn: this is called early, before irq is set up. */
	notify_remote_via_evtchn(cons->evtchn);
	}

	static int __write_console(struct xencons_info *xencons,
	const char *data, int len)
	{
	XENCONS_RING_IDX cons, prod;
	struct xencons_interface *intf = xencons->intf;
	int sent = 0;

	cons = intf->out_cons;
	prod = intf->out_prod;
	mb(); /* update queue values before going on */
	BUG_ON((prod - cons) > sizeof(intf->out));

	while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
	intf->out[MASK_XENCONS_IDX(prod++, intf->out)] = data[sent++];

	wmb(); /* write ring before updating pointer */
	intf->out_prod = prod;

	if (sent)
	notify_daemon(xencons);
	return sent;
	}

	static int domU_write_console(uint32_t vtermno, const char *data, int len)
	{
	int ret = len;
	struct xencons_info *cons = vtermno_to_xencons(vtermno);
	if (cons == NULL)
	return -EINVAL;

	/*
	* Make sure the whole buffer is emitted, polling if
	* necessary. We don't ever want to rely on the hvc daemon
	* because the most interesting console output is when the
	* kernel is crippled.
	*/
	while (len) {
	int sent = __write_console(cons, data, len);

	data += sent;
	len -= sent;

	if (unlikely(len))
	HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
	}

	return ret;
	}

	static int domU_read_console(uint32_t vtermno, char *buf, int len)
	{
	struct xencons_interface *intf;
	XENCONS_RING_IDX cons, prod;
	int recv = 0;
	struct xencons_info *xencons = vtermno_to_xencons(vtermno);
	if (xencons == NULL)
	return -EINVAL;
	intf = xencons->intf;

	cons = intf->in_cons;
	prod = intf->in_prod;
	mb(); /* get pointers before reading ring */
	BUG_ON((prod - cons) > sizeof(intf->in));

	while (cons != prod && recv < len)
	buf[recv++] = intf->in[MASK_XENCONS_IDX(cons++, intf->in)];

	mb(); /* read ring before consuming */
	intf->in_cons = cons;

	notify_daemon(xencons);
	return recv;
	}

	static struct hv_ops domU_hvc_ops = {
	.get_chars = domU_read_console,
	.put_chars = domU_write_console,
	.notifier_add = notifier_add_irq,
	.notifier_del = notifier_del_irq,
	.notifier_hangup = notifier_hangup_irq,
	};

	static int dom0_read_console(uint32_t vtermno, char *buf, int len)
	{
	return HYPERVISOR_console_io(CONSOLEIO_read, len, buf);
	}

	/*
	* Either for a dom0 to write to the system console, or a domU with a
	* debug version of Xen
	*/
	static int dom0_write_console(uint32_t vtermno, const char *str, int len)
	{
	int rc = HYPERVISOR_console_io(CONSOLEIO_write, len, (char *)str);
	if (rc < 0)
	return 0;

	return len;
	}

	static struct hv_ops dom0_hvc_ops = {
	.get_chars = dom0_read_console,
	.put_chars = dom0_write_console,
	.notifier_add = notifier_add_irq,
	.notifier_del = notifier_del_irq,
	.notifier_hangup = notifier_hangup_irq,
	};

	static int xen_hvm_console_init(void)
	{
	int r;
	uint64_t v = 0;
	unsigned long mfn;
	struct xencons_info *info;

	if (!xen_hvm_domain())
	return -ENODEV;

	info = vtermno_to_xencons(HVC_COOKIE);
	if (!info) {
	info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
	if (!info)
	return -ENOMEM;
	} else if (info->intf != NULL) {
	/* already configured */
	return 0;
	}
	/*
	* If the toolstack (or the hypervisor) hasn't set these values, the
	* default value is 0. Even though mfn = 0 and evtchn = 0 are
	* theoretically correct values, in practice they never are and they
	* mean that a legacy toolstack hasn't initialized the pv console correctly.
	*/
	r = hvm_get_parameter(HVM_PARAM_CONSOLE_EVTCHN, &v);
	if (r < 0 \|\| v == 0)
	goto err;
	info->evtchn = v;
	v = 0;
	r = hvm_get_parameter(HVM_PARAM_CONSOLE_PFN, &v);
	if (r < 0 \|\| v == 0)
	goto err;
	mfn = v;
	info->intf = xen_remap(mfn << PAGE_SHIFT, PAGE_SIZE);
	if (info->intf == NULL)
	goto err;
	info->vtermno = HVC_COOKIE;

	spin_lock(&xencons_lock);
	list_add_tail(&info->list, &xenconsoles);
	spin_unlock(&xencons_lock);

	return 0;
	err:
	kfree(info);
	return -ENODEV;
	}

	static int xen_pv_console_init(void)
	{
	struct xencons_info *info;

	if (!xen_pv_domain())
	return -ENODEV;

	if (!xen_start_info->console.domU.evtchn)
	return -ENODEV;

	info = vtermno_to_xencons(HVC_COOKIE);
	if (!info) {
	info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
	if (!info)
	return -ENOMEM;
	} else if (info->intf != NULL) {
	/* already configured */
	return 0;
	}
	info->evtchn = xen_start_info->console.domU.evtchn;
	info->intf = mfn_to_virt(xen_start_info->console.domU.mfn);
	info->vtermno = HVC_COOKIE;

	spin_lock(&xencons_lock);
	list_add_tail(&info->list, &xenconsoles);
	spin_unlock(&xencons_lock);

	return 0;
	}

	static int xen_initial_domain_console_init(void)
	{
	struct xencons_info *info;

	if (!xen_initial_domain())
	return -ENODEV;

	info = vtermno_to_xencons(HVC_COOKIE);
	if (!info) {
	info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
	if (!info)
	return -ENOMEM;
	}

	info->irq = bind_virq_to_irq(VIRQ_CONSOLE, 0);
	info->vtermno = HVC_COOKIE;

	spin_lock(&xencons_lock);
	list_add_tail(&info->list, &xenconsoles);
	spin_unlock(&xencons_lock);

	return 0;
	}

	void xen_console_resume(void)
	{
	struct xencons_info *info = vtermno_to_xencons(HVC_COOKIE);
	if (info != NULL && info->irq)
	rebind_evtchn_irq(info->evtchn, info->irq);
	}

	static void xencons_disconnect_backend(struct xencons_info *info)
	{
	if (info->irq > 0)
	unbind_from_irqhandler(info->irq, NULL);
	info->irq = 0;
	if (info->evtchn > 0)
	xenbus_free_evtchn(info->xbdev, info->evtchn);
	info->evtchn = 0;
	if (info->gntref > 0)
	gnttab_free_grant_references(info->gntref);
	info->gntref = 0;
	if (info->hvc != NULL)
	hvc_remove(info->hvc);
	info->hvc = NULL;
	}

	static void xencons_free(struct xencons_info *info)
	{
	free_page((unsigned long)info->intf);
	info->intf = NULL;
	info->vtermno = 0;
	kfree(info);
	}

	static int xen_console_remove(struct xencons_info *info)
	{
	xencons_disconnect_backend(info);
	spin_lock(&xencons_lock);
	list_del(&info->list);
	spin_unlock(&xencons_lock);
	if (info->xbdev != NULL)
	xencons_free(info);
	else {
	if (xen_hvm_domain())
	iounmap(info->intf);
	kfree(info);
	}
	return 0;
	}

	#ifdef CONFIG_HVC_XEN_FRONTEND
	static struct xenbus_driver xencons_driver;

	static int xencons_remove(struct xenbus_device *dev)
	{
	return xen_console_remove(dev_get_drvdata(&dev->dev));
	}

	static int xencons_connect_backend(struct xenbus_device *dev,
	struct xencons_info *info)
	{
	int ret, evtchn, devid, ref, irq;
	struct xenbus_transaction xbt;
	grant_ref_t gref_head;
	unsigned long mfn;

	ret = xenbus_alloc_evtchn(dev, &evtchn);
	if (ret)
	return ret;
	info->evtchn = evtchn;
	irq = bind_evtchn_to_irq(evtchn);
	if (irq < 0)
	return irq;
	info->irq = irq;
	devid = dev->nodename[strlen(dev->nodename) - 1] - '0';
	info->hvc = hvc_alloc(xenbus_devid_to_vtermno(devid),
	irq, &domU_hvc_ops, 256);
	if (IS_ERR(info->hvc))
	return PTR_ERR(info->hvc);
	if (xen_pv_domain())
	mfn = virt_to_mfn(info->intf);
	else
	mfn = __pa(info->intf) >> PAGE_SHIFT;
	ret = gnttab_alloc_grant_references(1, &gref_head);
	if (ret < 0)
	return ret;
	info->gntref = gref_head;
	ref = gnttab_claim_grant_reference(&gref_head);
	if (ref < 0)
	return ref;
	gnttab_grant_foreign_access_ref(ref, info->xbdev->otherend_id,
	mfn, 0);

	again:
	ret = xenbus_transaction_start(&xbt);
	if (ret) {
	xenbus_dev_fatal(dev, ret, "starting transaction");
	return ret;
	}
	ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", ref);
	if (ret)
	goto error_xenbus;
	ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
	evtchn);
	if (ret)
	goto error_xenbus;
	ret = xenbus_printf(xbt, dev->nodename, "type", "ioemu");
	if (ret)
	goto error_xenbus;
	ret = xenbus_transaction_end(xbt, 0);
	if (ret) {
	if (ret == -EAGAIN)
	goto again;
	xenbus_dev_fatal(dev, ret, "completing transaction");
	return ret;
	}

	xenbus_switch_state(dev, XenbusStateInitialised);
	return 0;

	error_xenbus:
	xenbus_transaction_end(xbt, 1);
	xenbus_dev_fatal(dev, ret, "writing xenstore");
	return ret;
	}

	static int xencons_probe(struct xenbus_device *dev,
	const struct xenbus_device_id *id)
	{
	int ret, devid;
	struct xencons_info *info;

	devid = dev->nodename[strlen(dev->nodename) - 1] - '0';
	if (devid == 0)
	return -ENODEV;

	info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
	if (!info)
	return -ENOMEM;
	dev_set_drvdata(&dev->dev, info);
	info->xbdev = dev;
	info->vtermno = xenbus_devid_to_vtermno(devid);
	info->intf = (void *)__get_free_page(GFP_KERNEL \| __GFP_ZERO);
	if (!info->intf)
	goto error_nomem;

	ret = xencons_connect_backend(dev, info);
	if (ret < 0)
	goto error;
	spin_lock(&xencons_lock);
	list_add_tail(&info->list, &xenconsoles);
	spin_unlock(&xencons_lock);

	return 0;

	error_nomem:
	ret = -ENOMEM;
	xenbus_dev_fatal(dev, ret, "allocating device memory");
	error:
	xencons_disconnect_backend(info);
	xencons_free(info);
	return ret;
	}

	static int xencons_resume(struct xenbus_device *dev)
	{
	struct xencons_info *info = dev_get_drvdata(&dev->dev);

	xencons_disconnect_backend(info);
	memset(info->intf, 0, PAGE_SIZE);
	return xencons_connect_backend(dev, info);
	}

	static void xencons_backend_changed(struct xenbus_device *dev,
	enum xenbus_state backend_state)
	{
	switch (backend_state) {
	case XenbusStateReconfiguring:
	case XenbusStateReconfigured:
	case XenbusStateInitialising:
	case XenbusStateInitialised:
	case XenbusStateUnknown:
	break;

	case XenbusStateInitWait:
	break;

	case XenbusStateConnected:
	xenbus_switch_state(dev, XenbusStateConnected);
	break;

	case XenbusStateClosed:
	if (dev->state == XenbusStateClosed)
	break;
	/* Missed the backend's CLOSING state -- fallthrough */
	case XenbusStateClosing:
	xenbus_frontend_closed(dev);
	break;
	}
	}

	static const struct xenbus_device_id xencons_ids[] = {
	{ "console" },
	{ "" }
	};


	static DEFINE_XENBUS_DRIVER(xencons, "xenconsole",
	.probe = xencons_probe,
	.remove = xencons_remove,
	.resume = xencons_resume,
	.otherend_changed = xencons_backend_changed,
	);
	#endif /* CONFIG_HVC_XEN_FRONTEND */

	static int __init xen_hvc_init(void)
	{
	int r;
	struct xencons_info *info;
	const struct hv_ops *ops;

	if (!xen_domain())
	return -ENODEV;

	if (xen_initial_domain()) {
	ops = &dom0_hvc_ops;
	r = xen_initial_domain_console_init();
	if (r < 0)
	return r;
	info = vtermno_to_xencons(HVC_COOKIE);
	} else {
	ops = &domU_hvc_ops;
	if (xen_hvm_domain())
	r = xen_hvm_console_init();
	else
	r = xen_pv_console_init();
	if (r < 0)
	return r;

	info = vtermno_to_xencons(HVC_COOKIE);
	info->irq = bind_evtchn_to_irq(info->evtchn);
	}
	if (info->irq < 0)
	info->irq = 0; /* NO_IRQ */
	else
	irq_set_noprobe(info->irq);

	info->hvc = hvc_alloc(HVC_COOKIE, info->irq, ops, 256);
	if (IS_ERR(info->hvc)) {
	r = PTR_ERR(info->hvc);
	spin_lock(&xencons_lock);
	list_del(&info->list);
	spin_unlock(&xencons_lock);
	if (info->irq)
	unbind_from_irqhandler(info->irq, NULL);
	kfree(info);
	return r;
	}

	r = 0;
	#ifdef CONFIG_HVC_XEN_FRONTEND
	r = xenbus_register_frontend(&xencons_driver);
	#endif
	return r;
	}

	static void __exit xen_hvc_fini(void)
	{
	struct xencons_info entry, next;

	if (list_empty(&xenconsoles))
	return;

	list_for_each_entry_safe(entry, next, &xenconsoles, list) {
	xen_console_remove(entry);
	}
	}

	static int xen_cons_init(void)
	{
	const struct hv_ops *ops;

	if (!xen_domain())
	return 0;

	if (xen_initial_domain())
	ops = &dom0_hvc_ops;
	else {
	int r;
	ops = &domU_hvc_ops;

	if (xen_hvm_domain())
	r = xen_hvm_console_init();
	else
	r = xen_pv_console_init();
	if (r < 0)
	return r;
	}

	hvc_instantiate(HVC_COOKIE, 0, ops);
	return 0;
	}


	module_init(xen_hvc_init);
	module_exit(xen_hvc_fini);
	console_initcall(xen_cons_init);

	#ifdef CONFIG_EARLY_PRINTK
	static void xenboot_write_console(struct console console, const char string,
	unsigned len)
	{
	unsigned int linelen, off = 0;
	const char *pos;

	if (!xen_pv_domain())
	return;

	dom0_write_console(0, string, len);

	if (xen_initial_domain())
	return;

	domU_write_console(0, "(early) ", 8);
	while (off < len && NULL != (pos = strchr(string+off, '\n'))) {
	linelen = pos-string+off;
	if (off + linelen > len)
	break;
	domU_write_console(0, string+off, linelen);
	domU_write_console(0, "\r\n", 2);
	off += linelen + 1;
	}
	if (off < len)
	domU_write_console(0, string+off, len-off);
	}

	struct console xenboot_console = {
	.name = "xenboot",
	.write = xenboot_write_console,
	.flags = CON_PRINTBUFFER \| CON_BOOT \| CON_ANYTIME,
	.index = -1,
	};
	#endif /* CONFIG_EARLY_PRINTK */

	void xen_raw_console_write(const char *str)
	{
	dom0_write_console(0, str, strlen(str));
	}

	void xen_raw_printk(const char *fmt, ...)
	{
	static char buf[512];
	va_list ap;

	va_start(ap, fmt);
	vsnprintf(buf, sizeof(buf), fmt, ap);
	va_end(ap);

	xen_raw_console_write(buf);
	}