linux/drivers/xen/xenbus/xenbus_probe_frontend.c
Konrad Rzeszutek Wilk 3066616ce2 xen/xenbus: Add quirk to deal with misconfigured backends.
A rather annoying and common case is when booting a PVonHVM guest
and exposing the PV KBD and PV VFB - as broken toolstacks don't
always initialize the backends correctly.

Normally The HVM guest is using the VGA driver and the emulated
keyboard for this (though upstream version of QEMU implements
PV KBD, but still uses a VGA driver). We provide a very basic
two-stage wait mechanism - where we wait for 30 seconds for all
devices, and then for 270 for all them except the two mentioned.

That allows us to wait for the essential devices, like network
or disk for the full 6 minutes.

To trigger this, put this in your guest config:

vfb = [ 'vnc=1, vnclisten=0.0.0.0 ,vncunused=1']

instead of this:
vnc=1
vnclisten="0.0.0.0"

CC: stable@kernel.org
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
[v3: Split delay in non-essential (30 seconds) and essential
 devices per Ian and Stefano suggestion]
[v4: Added comments per Stefano suggestion]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-04-19 12:45:01 -04:00

461 lines
12 KiB
C

#define DPRINTK(fmt, args...) \
pr_debug("xenbus_probe (%s:%d) " fmt ".\n", \
__func__, __LINE__, ##args)
#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/proc_fs.h>
#include <linux/notifier.h>
#include <linux/kthread.h>
#include <linux/mutex.h>
#include <linux/io.h>
#include <linux/module.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/xen/hypervisor.h>
#include <xen/xenbus.h>
#include <xen/events.h>
#include <xen/page.h>
#include <xen/platform_pci.h>
#include "xenbus_comms.h"
#include "xenbus_probe.h"
/* device/<type>/<id> => <type>-<id> */
static int frontend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
{
nodename = strchr(nodename, '/');
if (!nodename || strlen(nodename + 1) >= XEN_BUS_ID_SIZE) {
printk(KERN_WARNING "XENBUS: bad frontend %s\n", nodename);
return -EINVAL;
}
strlcpy(bus_id, nodename + 1, XEN_BUS_ID_SIZE);
if (!strchr(bus_id, '/')) {
printk(KERN_WARNING "XENBUS: bus_id %s no slash\n", bus_id);
return -EINVAL;
}
*strchr(bus_id, '/') = '-';
return 0;
}
/* device/<typename>/<name> */
static int xenbus_probe_frontend(struct xen_bus_type *bus, const char *type,
const char *name)
{
char *nodename;
int err;
/* ignore console/0 */
if (!strncmp(type, "console", 7) && !strncmp(name, "0", 1)) {
DPRINTK("Ignoring buggy device entry console/0");
return 0;
}
nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, name);
if (!nodename)
return -ENOMEM;
DPRINTK("%s", nodename);
err = xenbus_probe_node(bus, type, nodename);
kfree(nodename);
return err;
}
static int xenbus_uevent_frontend(struct device *_dev,
struct kobj_uevent_env *env)
{
struct xenbus_device *dev = to_xenbus_device(_dev);
if (add_uevent_var(env, "MODALIAS=xen:%s", dev->devicetype))
return -ENOMEM;
return 0;
}
static void backend_changed(struct xenbus_watch *watch,
const char **vec, unsigned int len)
{
xenbus_otherend_changed(watch, vec, len, 1);
}
static const struct dev_pm_ops xenbus_pm_ops = {
.suspend = xenbus_dev_suspend,
.resume = xenbus_dev_resume,
.freeze = xenbus_dev_suspend,
.thaw = xenbus_dev_cancel,
.restore = xenbus_dev_resume,
};
static struct xen_bus_type xenbus_frontend = {
.root = "device",
.levels = 2, /* device/type/<id> */
.get_bus_id = frontend_bus_id,
.probe = xenbus_probe_frontend,
.otherend_changed = backend_changed,
.bus = {
.name = "xen",
.match = xenbus_match,
.uevent = xenbus_uevent_frontend,
.probe = xenbus_dev_probe,
.remove = xenbus_dev_remove,
.shutdown = xenbus_dev_shutdown,
.dev_attrs = xenbus_dev_attrs,
.pm = &xenbus_pm_ops,
},
};
static void frontend_changed(struct xenbus_watch *watch,
const char **vec, unsigned int len)
{
DPRINTK("");
xenbus_dev_changed(vec[XS_WATCH_PATH], &xenbus_frontend);
}
/* We watch for devices appearing and vanishing. */
static struct xenbus_watch fe_watch = {
.node = "device",
.callback = frontend_changed,
};
static int read_backend_details(struct xenbus_device *xendev)
{
return xenbus_read_otherend_details(xendev, "backend-id", "backend");
}
static int is_device_connecting(struct device *dev, void *data, bool ignore_nonessential)
{
struct xenbus_device *xendev = to_xenbus_device(dev);
struct device_driver *drv = data;
struct xenbus_driver *xendrv;
/*
* A device with no driver will never connect. We care only about
* devices which should currently be in the process of connecting.
*/
if (!dev->driver)
return 0;
/* Is this search limited to a particular driver? */
if (drv && (dev->driver != drv))
return 0;
if (ignore_nonessential) {
/* With older QEMU, for PVonHVM guests the guest config files
* could contain: vfb = [ 'vnc=1, vnclisten=0.0.0.0']
* which is nonsensical as there is no PV FB (there can be
* a PVKB) running as HVM guest. */
if ((strncmp(xendev->nodename, "device/vkbd", 11) == 0))
return 0;
if ((strncmp(xendev->nodename, "device/vfb", 10) == 0))
return 0;
}
xendrv = to_xenbus_driver(dev->driver);
return (xendev->state < XenbusStateConnected ||
(xendev->state == XenbusStateConnected &&
xendrv->is_ready && !xendrv->is_ready(xendev)));
}
static int essential_device_connecting(struct device *dev, void *data)
{
return is_device_connecting(dev, data, true /* ignore PV[KBB+FB] */);
}
static int non_essential_device_connecting(struct device *dev, void *data)
{
return is_device_connecting(dev, data, false);
}
static int exists_essential_connecting_device(struct device_driver *drv)
{
return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
essential_device_connecting);
}
static int exists_non_essential_connecting_device(struct device_driver *drv)
{
return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
non_essential_device_connecting);
}
static int print_device_status(struct device *dev, void *data)
{
struct xenbus_device *xendev = to_xenbus_device(dev);
struct device_driver *drv = data;
/* Is this operation limited to a particular driver? */
if (drv && (dev->driver != drv))
return 0;
if (!dev->driver) {
/* Information only: is this too noisy? */
printk(KERN_INFO "XENBUS: Device with no driver: %s\n",
xendev->nodename);
} else if (xendev->state < XenbusStateConnected) {
enum xenbus_state rstate = XenbusStateUnknown;
if (xendev->otherend)
rstate = xenbus_read_driver_state(xendev->otherend);
printk(KERN_WARNING "XENBUS: Timeout connecting "
"to device: %s (local state %d, remote state %d)\n",
xendev->nodename, xendev->state, rstate);
}
return 0;
}
/* We only wait for device setup after most initcalls have run. */
static int ready_to_wait_for_devices;
static bool wait_loop(unsigned long start, unsigned int max_delay,
unsigned int *seconds_waited)
{
if (time_after(jiffies, start + (*seconds_waited+5)*HZ)) {
if (!*seconds_waited)
printk(KERN_WARNING "XENBUS: Waiting for "
"devices to initialise: ");
*seconds_waited += 5;
printk("%us...", max_delay - *seconds_waited);
if (*seconds_waited == max_delay)
return true;
}
schedule_timeout_interruptible(HZ/10);
return false;
}
/*
* On a 5-minute timeout, wait for all devices currently configured. We need
* to do this to guarantee that the filesystems and / or network devices
* needed for boot are available, before we can allow the boot to proceed.
*
* This needs to be on a late_initcall, to happen after the frontend device
* drivers have been initialised, but before the root fs is mounted.
*
* A possible improvement here would be to have the tools add a per-device
* flag to the store entry, indicating whether it is needed at boot time.
* This would allow people who knew what they were doing to accelerate their
* boot slightly, but of course needs tools or manual intervention to set up
* those flags correctly.
*/
static void wait_for_devices(struct xenbus_driver *xendrv)
{
unsigned long start = jiffies;
struct device_driver *drv = xendrv ? &xendrv->driver : NULL;
unsigned int seconds_waited = 0;
if (!ready_to_wait_for_devices || !xen_domain())
return;
while (exists_non_essential_connecting_device(drv))
if (wait_loop(start, 30, &seconds_waited))
break;
/* Skips PVKB and PVFB check.*/
while (exists_essential_connecting_device(drv))
if (wait_loop(start, 270, &seconds_waited))
break;
if (seconds_waited)
printk("\n");
bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
print_device_status);
}
int xenbus_register_frontend(struct xenbus_driver *drv)
{
int ret;
drv->read_otherend_details = read_backend_details;
ret = xenbus_register_driver_common(drv, &xenbus_frontend);
if (ret)
return ret;
/* If this driver is loaded as a module wait for devices to attach. */
wait_for_devices(drv);
return 0;
}
EXPORT_SYMBOL_GPL(xenbus_register_frontend);
static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
static int backend_state;
static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
const char **v, unsigned int l)
{
xenbus_scanf(XBT_NIL, v[XS_WATCH_PATH], "", "%i", &backend_state);
printk(KERN_DEBUG "XENBUS: backend %s %s\n",
v[XS_WATCH_PATH], xenbus_strstate(backend_state));
wake_up(&backend_state_wq);
}
static void xenbus_reset_wait_for_backend(char *be, int expected)
{
long timeout;
timeout = wait_event_interruptible_timeout(backend_state_wq,
backend_state == expected, 5 * HZ);
if (timeout <= 0)
printk(KERN_INFO "XENBUS: backend %s timed out.\n", be);
}
/*
* Reset frontend if it is in Connected or Closed state.
* Wait for backend to catch up.
* State Connected happens during kdump, Closed after kexec.
*/
static void xenbus_reset_frontend(char *fe, char *be, int be_state)
{
struct xenbus_watch be_watch;
printk(KERN_DEBUG "XENBUS: backend %s %s\n",
be, xenbus_strstate(be_state));
memset(&be_watch, 0, sizeof(be_watch));
be_watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", be);
if (!be_watch.node)
return;
be_watch.callback = xenbus_reset_backend_state_changed;
backend_state = XenbusStateUnknown;
printk(KERN_INFO "XENBUS: triggering reconnect on %s\n", be);
register_xenbus_watch(&be_watch);
/* fall through to forward backend to state XenbusStateInitialising */
switch (be_state) {
case XenbusStateConnected:
xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosing);
xenbus_reset_wait_for_backend(be, XenbusStateClosing);
case XenbusStateClosing:
xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed);
xenbus_reset_wait_for_backend(be, XenbusStateClosed);
case XenbusStateClosed:
xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateInitialising);
xenbus_reset_wait_for_backend(be, XenbusStateInitWait);
}
unregister_xenbus_watch(&be_watch);
printk(KERN_INFO "XENBUS: reconnect done on %s\n", be);
kfree(be_watch.node);
}
static void xenbus_check_frontend(char *class, char *dev)
{
int be_state, fe_state, err;
char *backend, *frontend;
frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
if (!frontend)
return;
err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &fe_state);
if (err != 1)
goto out;
switch (fe_state) {
case XenbusStateConnected:
case XenbusStateClosed:
printk(KERN_DEBUG "XENBUS: frontend %s %s\n",
frontend, xenbus_strstate(fe_state));
backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
if (!backend || IS_ERR(backend))
goto out;
err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &be_state);
if (err == 1)
xenbus_reset_frontend(frontend, backend, be_state);
kfree(backend);
break;
default:
break;
}
out:
kfree(frontend);
}
static void xenbus_reset_state(void)
{
char **devclass, **dev;
int devclass_n, dev_n;
int i, j;
devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
if (IS_ERR(devclass))
return;
for (i = 0; i < devclass_n; i++) {
dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
if (IS_ERR(dev))
continue;
for (j = 0; j < dev_n; j++)
xenbus_check_frontend(devclass[i], dev[j]);
kfree(dev);
}
kfree(devclass);
}
static int frontend_probe_and_watch(struct notifier_block *notifier,
unsigned long event,
void *data)
{
/* reset devices in Connected or Closed state */
if (xen_hvm_domain())
xenbus_reset_state();
/* Enumerate devices in xenstore and watch for changes. */
xenbus_probe_devices(&xenbus_frontend);
register_xenbus_watch(&fe_watch);
return NOTIFY_DONE;
}
static int __init xenbus_probe_frontend_init(void)
{
static struct notifier_block xenstore_notifier = {
.notifier_call = frontend_probe_and_watch
};
int err;
DPRINTK("");
/* Register ourselves with the kernel bus subsystem */
err = bus_register(&xenbus_frontend.bus);
if (err)
return err;
register_xenstore_notifier(&xenstore_notifier);
return 0;
}
subsys_initcall(xenbus_probe_frontend_init);
#ifndef MODULE
static int __init boot_wait_for_devices(void)
{
if (xen_hvm_domain() && !xen_platform_pci_unplug)
return -ENODEV;
ready_to_wait_for_devices = 1;
wait_for_devices(NULL);
return 0;
}
late_initcall(boot_wait_for_devices);
#endif
MODULE_LICENSE("GPL");