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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