linux/drivers/char/hvc_xen.c
Jeremy Fitzhardinge 7825cf10e3 xen/hvc: make sure console output is always emitted, with explicit polling
We never want to rely on the hvc workqueue to emit output, because the
most interesting output is when the kernel is broken.  This will
improve oops/crash/console message for better debugging.

Instead, we force-poll until all output is emitted.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stable Kernel <stable@kernel.org>
2009-11-03 11:05:51 -08:00

237 lines
5.4 KiB
C

/*
* 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/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 unsigned long console_pfn = ~0ul;
static inline struct xencons_interface *xencons_interface(void)
{
if (console_pfn == ~0ul)
return mfn_to_virt(xen_start_info->console.domU.mfn);
else
return __va(console_pfn << PAGE_SHIFT);
}
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(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 write_console(uint32_t vtermno, const char *data, int len)
{
int ret = len;
/*
* 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(data, len);
data += sent;
len -= sent;
if (unlikely(len))
HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
}
return ret;
}
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,
.notifier_add = notifier_add_irq,
.notifier_del = notifier_del_irq,
.notifier_hangup = notifier_hangup_irq,
};
static int __init xen_init(void)
{
struct hvc_struct *hp;
if (!xen_pv_domain() ||
xen_initial_domain() ||
!xen_start_info->console.domU.evtchn)
return -ENODEV;
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;
console_pfn = mfn_to_pfn(xen_start_info->console.domU.mfn);
return 0;
}
void xen_console_resume(void)
{
if (xencons_irq)
rebind_evtchn_irq(xen_start_info->console.domU.evtchn, xencons_irq);
}
static void __exit xen_fini(void)
{
if (hvc)
hvc_remove(hvc);
}
static int xen_cons_init(void)
{
if (!xen_pv_domain())
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 raw_console_write(const char *str, int len)
{
while(len > 0) {
int rc = HYPERVISOR_console_io(CONSOLEIO_write, len, (char *)str);
if (rc <= 0)
break;
str += rc;
len -= rc;
}
}
#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;
raw_console_write(string, len);
write_console(0, "(early) ", 8);
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 | CON_ANYTIME,
};
#endif /* CONFIG_EARLY_PRINTK */
void xen_raw_console_write(const char *str)
{
raw_console_write(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);
}