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Subject[patch 17/21] Xen-paravirt: Add the Xen virtual console driver.
This provides a bootstrap and ongoing emergency console which is
intended to be available from very early during boot and at all times
thereafter, in contrast with alternatives such as UDP-based syslogd,
or logging in via ssh. The protocol is based on a simple shared-memory
ring buffer.

Signed-off-by: Ian Pratt <ian.pratt@xensource.com>
Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: Alan <alan@lxorguk.ukuu.org.uk>

---
arch/i386/kernel/early_printk.c | 2
drivers/Makefile | 3
drivers/xen/Makefile | 1
drivers/xen/console/Makefile | 2
drivers/xen/console/console.c | 585 +++++++++++++++++++++++++++++++++++
drivers/xen/console/xencons_ring.c | 144 ++++++++
include/xen/xencons.h | 14
init/main.c | 2
8 files changed, 753 insertions(+)
===================================================================
--- a/arch/i386/kernel/early_printk.c
+++ b/arch/i386/kernel/early_printk.c
@@ -1,2 +1,4 @@

+#ifndef CONFIG_XEN
#include "../../x86_64/kernel/early_printk.c"
+#endif
===================================================================
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -14,6 +14,9 @@ obj-$(CONFIG_ACPI) += acpi/
# was used and do nothing if so
obj-$(CONFIG_PNP) += pnp/
obj-$(CONFIG_ARM_AMBA) += amba/
+
+# Xen is the default console when running as a guest
+obj-$(CONFIG_XEN) += xen/

# char/ comes before serial/ etc so that the VT console is the boot-time
# default.
===================================================================
--- /dev/null
+++ b/drivers/xen/Makefile
@@ -0,0 +1,1 @@
+obj-y += console/
===================================================================
--- /dev/null
+++ b/drivers/xen/console/Makefile
@@ -0,0 +1,2 @@
+
+obj-y := console.o xencons_ring.o
===================================================================
--- /dev/null
+++ b/drivers/xen/console/console.c
@@ -0,0 +1,585 @@
+/******************************************************************************
+ * console.c
+ *
+ * Virtual console driver.
+ *
+ * Copyright (c) 2002-2004, K A Fraser.
+ *
+ * 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.
+ */
+
+#include <linux/version.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/serial.h>
+#include <linux/major.h>
+#include <linux/ptrace.h>
+#include <linux/ioport.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/console.h>
+#include <linux/bootmem.h>
+#include <linux/sysrq.h>
+#include <linux/vt.h>
+
+#include <asm/io.h>
+#include <asm/irq.h>
+#include <asm/uaccess.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/event_channel.h>
+#include <asm/xen/hypervisor.h>
+#include <xen/events.h>
+#include <xen/xencons.h>
+
+MODULE_LICENSE("Dual BSD/GPL");
+
+static int xc_disabled = 0;
+static int xc_num = -1;
+
+/* /dev/xvc0 device number allocated by lanana.org. */
+#define XEN_XVC_MAJOR 204
+#define XEN_XVC_MINOR 191
+
+#ifdef CONFIG_MAGIC_SYSRQ
+static unsigned long sysrq_requested;
+#endif
+
+static int __init xencons_setup(char *str)
+{
+ if (!strcmp(str, "off"))
+ xc_disabled = 1;
+ return 1;
+}
+__setup("xencons=", xencons_setup);
+
+/* The kernel and user-land drivers share a common transmit buffer. */
+static unsigned int wbuf_size = 4096;
+#define WBUF_MASK(_i) ((_i)&(wbuf_size-1))
+static char *wbuf;
+static unsigned int wc, wp; /* write_cons, write_prod */
+
+static int __init xencons_bufsz_setup(char *str)
+{
+ unsigned int goal;
+ goal = simple_strtoul(str, NULL, 0);
+ if (goal) {
+ goal = roundup_pow_of_two(goal);
+ if (wbuf_size < goal)
+ wbuf_size = goal;
+ }
+ return 1;
+}
+__setup("xencons_bufsz=", xencons_bufsz_setup);
+
+/* This lock protects accesses to the common transmit buffer. */
+static DEFINE_SPINLOCK(xencons_lock);
+
+/* Common transmit-kick routine. */
+static void __xencons_tx_flush(void);
+
+static struct tty_driver *xencons_driver;
+
+/******************** Kernel console driver ********************************/
+
+static void kcons_write(struct console *c, const char *s, unsigned int count)
+{
+ int i = 0;
+ unsigned long flags;
+
+ spin_lock_irqsave(&xencons_lock, flags);
+
+ while (i < count) {
+ for (; i < count; i++) {
+ if ((wp - wc) >= (wbuf_size - 1))
+ break;
+ if ((wbuf[WBUF_MASK(wp++)] = s[i]) == '\n')
+ wbuf[WBUF_MASK(wp++)] = '\r';
+ }
+
+ __xencons_tx_flush();
+ }
+
+ spin_unlock_irqrestore(&xencons_lock, flags);
+}
+
+static void kcons_write_dom0(struct console *c, const char *s, unsigned int count)
+{
+ while (count > 0) {
+ int rc;
+ rc = HYPERVISOR_console_io(CONSOLEIO_write, count, (char *)s);
+ if (rc <= 0)
+ break;
+ count -= rc;
+ s += rc;
+ }
+}
+
+void early_printk(const char *fmt, ...)
+{
+ va_list args;
+ int printk_len;
+ static char printk_buf[1024];
+
+ /* Emit the output into the temporary buffer */
+ va_start(args, fmt);
+ printk_len = vsnprintf(printk_buf, sizeof(printk_buf), fmt, args);
+ va_end(args);
+
+ /* Send the processed output directly to Xen. */
+ kcons_write_dom0(NULL, printk_buf, printk_len);
+}
+
+static struct console early_xen_console = {
+ .name = "earlyxen",
+ .write = kcons_write_dom0,
+ .flags = CON_PRINTBUFFER,
+ .index = -1,
+};
+
+static int early_console_initialized = 0;
+
+int __init setup_early_printk(char *opt)
+{
+ early_console_initialized = 1;
+ register_console(&early_xen_console);
+
+ return 0;
+}
+
+void __init disable_early_printk(void)
+{
+ if (!early_console_initialized)
+ return;
+ printk("disabling early console\n");
+ unregister_console(&early_xen_console);
+ early_console_initialized = 0;
+}
+
+static struct tty_driver *kcons_device(struct console *c, int *index)
+{
+ *index = 0;
+ return xencons_driver;
+}
+
+static struct console kcons_info = {
+ .name = "xvc",
+ .device = kcons_device,
+ .flags = CON_PRINTBUFFER | CON_ENABLED,
+ .index = -1,
+};
+
+static int __init xen_console_init(void)
+{
+ if (!is_running_on_xen())
+ goto out;
+ if (xc_disabled)
+ goto out;
+
+ if (is_initial_xendomain()) {
+ kcons_info.write = kcons_write_dom0;
+ } else {
+ if (!xen_start_info->console.domU.evtchn)
+ goto out;
+ kcons_info.write = kcons_write;
+ }
+ if (xc_num == -1)
+ xc_num = 0;
+
+ wbuf = alloc_bootmem(wbuf_size);
+
+ register_console(&kcons_info);
+
+out:
+ return 0;
+}
+console_initcall(xen_console_init);
+
+/*** Forcibly flush console data before dying. ***/
+void xencons_force_flush(void)
+{
+ int sz;
+
+ /* Emergency console is synchronous, so there's nothing to flush. */
+ if (!is_running_on_xen() ||
+ is_initial_xendomain() ||
+ !xen_start_info->console.domU.evtchn)
+ return;
+
+ /* Spin until console data is flushed through to the daemon. */
+ while (wc != wp) {
+ int sent = 0;
+ if ((sz = wp - wc) == 0)
+ continue;
+ sent = xencons_ring_send(&wbuf[WBUF_MASK(wc)], sz);
+ if (sent > 0)
+ wc += sent;
+ }
+}
+
+
+/******************** User-space console driver (/dev/console) ************/
+
+#define DRV(_d) (_d)
+
+static struct ktermios *xencons_termios[1];
+static struct ktermios *xencons_termios_locked[1];
+static struct tty_struct *xencons_tty;
+static int xencons_priv_irq;
+static char x_char;
+
+void xencons_rx(char *buf, unsigned len)
+{
+ int i;
+ unsigned long flags;
+
+ spin_lock_irqsave(&xencons_lock, flags);
+ if (xencons_tty == NULL)
+ goto out;
+
+ for (i = 0; i < len; i++) {
+#ifdef CONFIG_MAGIC_SYSRQ
+ if (sysrq_on()) {
+ if (buf[i] == '\x0f') { /* ^O */
+ sysrq_requested = jiffies;
+ continue; /* don't print the sysrq key */
+ } else if (sysrq_requested) {
+ unsigned long sysrq_timeout =
+ sysrq_requested + HZ*2;
+ sysrq_requested = 0;
+ if (time_before(jiffies, sysrq_timeout)) {
+ spin_unlock_irqrestore(
+ &xencons_lock, flags);
+ handle_sysrq(
+ buf[i], xencons_tty);
+ spin_lock_irqsave(
+ &xencons_lock, flags);
+ continue;
+ }
+ }
+ }
+#endif
+ tty_insert_flip_char(xencons_tty, buf[i], TTY_NORMAL);
+ }
+ tty_flip_buffer_push(xencons_tty);
+
+ out:
+ spin_unlock_irqrestore(&xencons_lock, flags);
+}
+
+static void __xencons_tx_flush(void)
+{
+ int sent, sz, work_done = 0;
+
+ if (x_char) {
+ if (is_initial_xendomain())
+ kcons_write_dom0(NULL, &x_char, 1);
+ else
+ while (x_char)
+ if (xencons_ring_send(&x_char, 1) == 1)
+ break;
+ x_char = 0;
+ work_done = 1;
+ }
+
+ while (wc != wp) {
+ sz = wp - wc;
+ if (sz > (wbuf_size - WBUF_MASK(wc)))
+ sz = wbuf_size - WBUF_MASK(wc);
+ if (is_initial_xendomain()) {
+ kcons_write_dom0(NULL, &wbuf[WBUF_MASK(wc)], sz);
+ wc += sz;
+ } else {
+ sent = xencons_ring_send(&wbuf[WBUF_MASK(wc)], sz);
+ if (sent == 0)
+ break;
+ wc += sent;
+ }
+ work_done = 1;
+ }
+
+ if (work_done && (xencons_tty != NULL)) {
+ wake_up_interruptible(&xencons_tty->write_wait);
+ tty_wakeup(xencons_tty);
+ }
+}
+
+void xencons_tx(void)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&xencons_lock, flags);
+ __xencons_tx_flush();
+ spin_unlock_irqrestore(&xencons_lock, flags);
+}
+
+/* Privileged receive callback and transmit kicker. */
+static irqreturn_t xencons_priv_interrupt(int irq, void *dev_id)
+{
+ static char rbuf[16];
+ int l;
+
+ while ((l = HYPERVISOR_console_io(CONSOLEIO_read, 16, rbuf)) > 0)
+ xencons_rx(rbuf, l);
+
+ xencons_tx();
+
+ return IRQ_HANDLED;
+}
+
+static int xencons_write_room(struct tty_struct *tty)
+{
+ return wbuf_size - (wp - wc);
+}
+
+static int xencons_chars_in_buffer(struct tty_struct *tty)
+{
+ return wp - wc;
+}
+
+static void xencons_send_xchar(struct tty_struct *tty, char ch)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&xencons_lock, flags);
+ x_char = ch;
+ __xencons_tx_flush();
+ spin_unlock_irqrestore(&xencons_lock, flags);
+}
+
+static void xencons_throttle(struct tty_struct *tty)
+{
+ if (I_IXOFF(tty))
+ xencons_send_xchar(tty, STOP_CHAR(tty));
+}
+
+static void xencons_unthrottle(struct tty_struct *tty)
+{
+ if (I_IXOFF(tty)) {
+ if (x_char != 0)
+ x_char = 0;
+ else
+ xencons_send_xchar(tty, START_CHAR(tty));
+ }
+}
+
+static void xencons_flush_buffer(struct tty_struct *tty)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&xencons_lock, flags);
+ wc = wp = 0;
+ spin_unlock_irqrestore(&xencons_lock, flags);
+}
+
+static inline int __xencons_put_char(unsigned char ch)
+{
+ if ((wp - wc) == wbuf_size)
+ return 0;
+ wbuf[WBUF_MASK(wp++)] = ch;
+ return 1;
+}
+
+static int xencons_write(
+ struct tty_struct *tty,
+ const unsigned char *buf,
+ int count)
+{
+ int i;
+ unsigned long flags;
+
+ spin_lock_irqsave(&xencons_lock, flags);
+
+ for (i = 0; i < count; i++)
+ if (!__xencons_put_char(buf[i]))
+ break;
+
+ if (i != 0)
+ __xencons_tx_flush();
+
+ spin_unlock_irqrestore(&xencons_lock, flags);
+
+ return i;
+}
+
+static void xencons_put_char(struct tty_struct *tty, unsigned char ch)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&xencons_lock, flags);
+ (void)__xencons_put_char(ch);
+ spin_unlock_irqrestore(&xencons_lock, flags);
+}
+
+static void xencons_flush_chars(struct tty_struct *tty)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&xencons_lock, flags);
+ __xencons_tx_flush();
+ spin_unlock_irqrestore(&xencons_lock, flags);
+}
+
+static void xencons_wait_until_sent(struct tty_struct *tty, int timeout)
+{
+ unsigned long orig_jiffies = jiffies;
+
+ while (DRV(tty->driver)->chars_in_buffer(tty)) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_timeout(1);
+ if (signal_pending(current))
+ break;
+ if (timeout && time_after(jiffies, orig_jiffies + timeout))
+ break;
+ }
+
+ set_current_state(TASK_RUNNING);
+}
+
+static int xencons_open(struct tty_struct *tty, struct file *filp)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&xencons_lock, flags);
+ tty->driver_data = NULL;
+ if (xencons_tty == NULL)
+ xencons_tty = tty;
+ __xencons_tx_flush();
+ spin_unlock_irqrestore(&xencons_lock, flags);
+
+ return 0;
+}
+
+static void xencons_close(struct tty_struct *tty, struct file *filp)
+{
+ unsigned long flags;
+
+ mutex_lock(&tty_mutex);
+
+ if (tty->count != 1) {
+ mutex_unlock(&tty_mutex);
+ return;
+ }
+
+ /* Prevent other threads from re-opening this tty. */
+ set_bit(TTY_CLOSING, &tty->flags);
+ mutex_unlock(&tty_mutex);
+
+ tty->closing = 1;
+ tty_wait_until_sent(tty, 0);
+ if (DRV(tty->driver)->flush_buffer != NULL)
+ DRV(tty->driver)->flush_buffer(tty);
+ if (tty->ldisc.flush_buffer != NULL)
+ tty->ldisc.flush_buffer(tty);
+ tty->closing = 0;
+ spin_lock_irqsave(&xencons_lock, flags);
+ xencons_tty = NULL;
+ spin_unlock_irqrestore(&xencons_lock, flags);
+}
+
+static struct tty_operations xencons_ops = {
+ .open = xencons_open,
+ .close = xencons_close,
+ .write = xencons_write,
+ .write_room = xencons_write_room,
+ .put_char = xencons_put_char,
+ .flush_chars = xencons_flush_chars,
+ .chars_in_buffer = xencons_chars_in_buffer,
+ .send_xchar = xencons_send_xchar,
+ .flush_buffer = xencons_flush_buffer,
+ .throttle = xencons_throttle,
+ .unthrottle = xencons_unthrottle,
+ .wait_until_sent = xencons_wait_until_sent,
+};
+
+static int __init xencons_init(void)
+{
+ int rc;
+
+ if (!is_running_on_xen())
+ return -ENODEV;
+
+ if (xc_disabled)
+ return 0;
+
+ if (!is_initial_xendomain()) {
+ rc = xencons_ring_init();
+ if (rc)
+ return rc;
+ }
+
+ xencons_driver = alloc_tty_driver(1);
+ if (xencons_driver == NULL)
+ return -ENOMEM;
+
+ DRV(xencons_driver)->name = "xvc";
+ DRV(xencons_driver)->major = XEN_XVC_MAJOR;
+ DRV(xencons_driver)->minor_start = XEN_XVC_MINOR;
+ DRV(xencons_driver)->name_base = xc_num;
+ DRV(xencons_driver)->type = TTY_DRIVER_TYPE_SERIAL;
+ DRV(xencons_driver)->subtype = SERIAL_TYPE_NORMAL;
+ DRV(xencons_driver)->init_termios = tty_std_termios;
+ DRV(xencons_driver)->flags =
+ TTY_DRIVER_REAL_RAW |
+ TTY_DRIVER_RESET_TERMIOS |
+ TTY_DRIVER_DYNAMIC_DEV;
+ DRV(xencons_driver)->termios = xencons_termios;
+ DRV(xencons_driver)->termios_locked = xencons_termios_locked;
+
+ tty_set_operations(xencons_driver, &xencons_ops);
+
+ if ((rc = tty_register_driver(DRV(xencons_driver))) != 0) {
+ printk("WARNING: Failed to register Xen virtual "
+ "console driver as '%s%d'\n",
+ DRV(xencons_driver)->name,
+ DRV(xencons_driver)->name_base);
+ put_tty_driver(xencons_driver);
+ xencons_driver = NULL;
+ return rc;
+ }
+
+ if (is_initial_xendomain()) {
+ xencons_priv_irq = bind_virq_to_irqhandler(
+ VIRQ_CONSOLE,
+ 0,
+ xencons_priv_interrupt,
+ 0,
+ "console",
+ NULL);
+ BUG_ON(xencons_priv_irq < 0);
+ }
+
+ printk("Xen virtual console successfully installed as %s%d\n",
+ DRV(xencons_driver)->name, xc_num);
+
+ return 0;
+}
+
+module_init(xencons_init);
===================================================================
--- /dev/null
+++ b/drivers/xen/console/xencons_ring.c
@@ -0,0 +1,144 @@
+/*
+ * 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.
+ */
+
+#include <linux/version.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/serial.h>
+#include <linux/major.h>
+#include <linux/ptrace.h>
+#include <linux/ioport.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+
+#include <asm/xen/hypervisor.h>
+#include <linux/wait.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <linux/err.h>
+#include <xen/interface/io/console.h>
+#include <xen/events.h>
+#include <xen/xencons.h>
+#include <xen/page.h>
+
+static int xencons_irq;
+
+static inline struct xencons_interface *xencons_interface(void)
+{
+ return mfn_to_virt(xen_start_info->console.domU.mfn);
+}
+
+static inline void notify_daemon(void)
+{
+ /* Use evtchn: this is called early, before irq is set up. */
+ notify_remote_via_evtchn(xen_start_info->console.domU.evtchn);
+}
+
+int xencons_ring_send(const char *data, unsigned len)
+{
+ int sent = 0;
+ struct xencons_interface *intf = xencons_interface();
+ XENCONS_RING_IDX cons, prod;
+
+ cons = intf->out_cons;
+ prod = intf->out_prod;
+ mb();
+ 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();
+ intf->out_prod = prod;
+
+ notify_daemon();
+
+ return sent;
+}
+
+static irqreturn_t handle_input(int irq, void *unused)
+{
+ struct xencons_interface *intf = xencons_interface();
+ XENCONS_RING_IDX cons, prod;
+
+ cons = intf->in_cons;
+ prod = intf->in_prod;
+ mb();
+ BUG_ON((prod - cons) > sizeof(intf->in));
+
+ while (cons != prod) {
+ xencons_rx(intf->in+MASK_XENCONS_IDX(cons,intf->in), 1);
+ cons++;
+ }
+
+ mb();
+ intf->in_cons = cons;
+
+ notify_daemon();
+
+ xencons_tx();
+
+ return IRQ_HANDLED;
+}
+
+int xencons_ring_init(void)
+{
+ int irq;
+
+ if (xencons_irq)
+ unbind_from_irqhandler(xencons_irq, NULL);
+ xencons_irq = 0;
+
+ if (!is_running_on_xen() ||
+ is_initial_xendomain() ||
+ !xen_start_info->console.domU.evtchn)
+ return -ENODEV;
+
+ irq = bind_evtchn_to_irqhandler(
+ xen_start_info->console.domU.evtchn,
+ handle_input, 0, "xencons", NULL);
+ if (irq < 0) {
+ printk(KERN_ERR "XEN console request irq failed %i\n", irq);
+ return irq;
+ }
+
+ xencons_irq = irq;
+
+ /* In case we have in-flight data after save/restore... */
+ notify_daemon();
+
+ return 0;
+}
+
+void xencons_resume(void)
+{
+ (void)xencons_ring_init();
+}
===================================================================
--- /dev/null
+++ b/include/xen/xencons.h
@@ -0,0 +1,14 @@
+#ifndef __ASM_XENCONS_H__
+#define __ASM_XENCONS_H__
+
+void xencons_force_flush(void);
+void xencons_resume(void);
+
+/* Interrupt work hooks. Receive data, or kick data out. */
+void xencons_rx(char *buf, unsigned len);
+void xencons_tx(void);
+
+int xencons_ring_init(void);
+int xencons_ring_send(const char *data, unsigned len);
+
+#endif /* __ASM_XENCONS_H__ */
===================================================================
--- a/init/main.c
+++ b/init/main.c
@@ -495,6 +495,8 @@ asmlinkage void __init start_kernel(void
unwind_init();
lockdep_init();

+ //setup_early_printk(NULL);
+
local_irq_disable();
early_boot_irqs_off();
early_init_irq_lock_class();
--

-
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