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[Xen-devel] [patch 33/44] xen: use the hvc console infrastructure for Xe

To: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] [patch 33/44] xen: use the hvc console infrastructure for Xen console
From: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
Date: Mon, 16 Jul 2007 16:16:09 -0700
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Andi Kleen <ak@xxxxxxx>, lkml <linux-kernel@xxxxxxxxxxxxxxx>, Chris Wright <chrisw@xxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Olof Johansson <olof@xxxxxxxxx>, Ingo Molnar <mingo@xxxxxxx>
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Implement a Xen back-end for hvc console.

* * *
Add early printk support via hvc console, enable using
"earlyprintk=xen" on the kernel command line.

From: Gerd Hoffmann <kraxel@xxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
Acked-by: Ingo Molnar <mingo@xxxxxxx>
Acked-by: Olof Johansson <olof@xxxxxxxxx>

---
 arch/i386/xen/events.c            |    3 
 arch/x86_64/kernel/early_printk.c |    5 +
 drivers/char/Kconfig              |    8 +
 drivers/char/Makefile             |    1 
 drivers/char/hvc_xen.c            |  159 +++++++++++++++++++++++++++++++++++++
 include/xen/events.h              |    1 
 include/xen/hvc-console.h         |    6 +
 7 files changed, 182 insertions(+), 1 deletion(-)

===================================================================
--- a/arch/i386/xen/events.c
+++ b/arch/i386/xen/events.c
@@ -244,7 +244,7 @@ static int find_unbound_irq(void)
        return irq;
 }
 
-static int bind_evtchn_to_irq(unsigned int evtchn)
+int bind_evtchn_to_irq(unsigned int evtchn)
 {
        int irq;
 
@@ -269,6 +269,7 @@ static int bind_evtchn_to_irq(unsigned i
 
        return irq;
 }
+EXPORT_SYMBOL_GPL(bind_evtchn_to_irq);
 
 static int bind_ipi_to_irq(unsigned int ipi, unsigned int cpu)
 {
===================================================================
--- a/arch/x86_64/kernel/early_printk.c
+++ b/arch/x86_64/kernel/early_printk.c
@@ -6,6 +6,7 @@
 #include <asm/io.h>
 #include <asm/processor.h>
 #include <asm/fcntl.h>
+#include <xen/hvc-console.h>
 
 /* Simple VGA output */
 
@@ -242,6 +243,10 @@ static int __init setup_early_printk(cha
                simnow_init(buf + 6);
                early_console = &simnow_console;
                keep_early = 1;
+#ifdef CONFIG_HVC_XEN
+       } else if (!strncmp(buf, "xen", 3)) {
+               early_console = &xenboot_console;
+#endif
        }
 
        if (keep_early)
===================================================================
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -653,6 +653,14 @@ config HVC_BEAT
        help
          Toshiba's Cell Reference Set Beat Console device driver
 
+config HVC_XEN
+       bool "Xen Hypervisor Console support"
+       depends on XEN
+       select HVC_DRIVER
+       default y
+       help
+         Xen virtual console device driver
+
 config HVCS
        tristate "IBM Hypervisor Virtual Console Server support"
        depends on PPC_PSERIES
===================================================================
--- a/drivers/char/Makefile
+++ b/drivers/char/Makefile
@@ -47,6 +47,7 @@ obj-$(CONFIG_HVC_RTAS)                += hvc_rtas.o
 obj-$(CONFIG_HVC_RTAS)         += hvc_rtas.o
 obj-$(CONFIG_HVC_BEAT)         += hvc_beat.o
 obj-$(CONFIG_HVC_DRIVER)       += hvc_console.o
+obj-$(CONFIG_HVC_XEN)          += hvc_xen.o
 obj-$(CONFIG_RAW_DRIVER)       += raw.o
 obj-$(CONFIG_SGI_SNSC)         += snsc.o snsc_event.o
 obj-$(CONFIG_MSPEC)            += mspec.o
===================================================================
--- /dev/null
+++ b/drivers/char/hvc_xen.c
@@ -0,0 +1,159 @@
+/*
+ * xen console driver interface to hvc_console.c
+ *
+ * (c) 2007 Gerd Hoffmann <kraxel@xxxxxxx>
+ *
+ * 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/init.h>
+#include <linux/types.h>
+
+#include <asm/xen/hypervisor.h>
+#include <xen/page.h>
+#include <xen/events.h>
+#include <xen/interface/io/console.h>
+#include <xen/hvc-console.h>
+
+#include "hvc_console.h"
+
+#define HVC_COOKIE   0x58656e /* "Xen" in hex */
+
+static struct hvc_struct *hvc;
+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);
+}
+
+static int write_console(uint32_t vtermno, const char *data, int len)
+{
+       struct xencons_interface *intf = xencons_interface();
+       XENCONS_RING_IDX cons, prod;
+       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;
+
+       notify_daemon();
+       return sent;
+}
+
+static int read_console(uint32_t vtermno, char *buf, int len)
+{
+       struct xencons_interface *intf = xencons_interface();
+       XENCONS_RING_IDX cons, prod;
+       int recv = 0;
+
+       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();
+       return recv;
+}
+
+static struct hv_ops hvc_ops = {
+       .get_chars = read_console,
+       .put_chars = write_console,
+};
+
+static int __init xen_init(void)
+{
+       struct hvc_struct *hp;
+
+       if (!is_running_on_xen())
+               return 0;
+
+       xencons_irq = bind_evtchn_to_irq(xen_start_info->console.domU.evtchn);
+       if (xencons_irq < 0)
+               xencons_irq = 0 /* NO_IRQ */;
+       hp = hvc_alloc(HVC_COOKIE, xencons_irq, &hvc_ops, 256);
+       if (IS_ERR(hp))
+               return PTR_ERR(hp);
+
+       hvc = hp;
+       return 0;
+}
+
+static void __exit xen_fini(void)
+{
+       if (hvc)
+               hvc_remove(hvc);
+}
+
+static int xen_cons_init(void)
+{
+       if (!is_running_on_xen())
+               return 0;
+
+       hvc_instantiate(HVC_COOKIE, 0, &hvc_ops);
+       return 0;
+}
+
+module_init(xen_init);
+module_exit(xen_fini);
+console_initcall(xen_cons_init);
+
+static void xenboot_write_console(struct console *console, const char *string,
+                                 unsigned len)
+{
+       unsigned int linelen, off = 0;
+       const char *pos;
+
+       while (off < len && NULL != (pos = strchr(string+off, '\n'))) {
+               linelen = pos-string+off;
+               if (off + linelen > len)
+                       break;
+               write_console(0, string+off, linelen);
+               write_console(0, "\r\n", 2);
+               off += linelen + 1;
+       }
+       if (off < len)
+               write_console(0, string+off, len-off);
+}
+
+struct console xenboot_console = {
+       .name           = "xenboot",
+       .write          = xenboot_write_console,
+       .flags          = CON_PRINTBUFFER | CON_BOOT,
+};
===================================================================
--- a/include/xen/events.h
+++ b/include/xen/events.h
@@ -13,6 +13,7 @@ enum ipi_vector {
        XEN_NR_IPIS,
 };
 
+int bind_evtchn_to_irq(unsigned int evtchn);
 int bind_evtchn_to_irqhandler(unsigned int evtchn,
                              irq_handler_t handler,
                              unsigned long irqflags, const char *devname,
===================================================================
--- /dev/null
+++ b/include/xen/hvc-console.h
@@ -0,0 +1,6 @@
+#ifndef XEN_HVC_CONSOLE_H
+#define XEN_HVC_CONSOLE_H
+
+extern struct console xenboot_console;
+
+#endif /* XEN_HVC_CONSOLE_H */

-- 


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