linux/drivers/xen/manage.c
Jakub Kądziołka ff32baa1f3 xen: don't hang when resuming PCI device
If a xen domain with at least two VCPUs has a PCI device attached which
enters the D3hot state during suspend, the kernel may hang while
resuming, depending on the core on which an async resume task gets
scheduled.

The bug occurs because xen's do_suspend calls dpm_resume_start while
only the timer of the boot CPU has been resumed (when xen_suspend called
syscore_resume), before calling xen_arch_suspend to resume the timers of
the other CPUs. This breaks pci_dev_d3_sleep.

Thus this patch moves the call to xen_arch_resume before the call to
dpm_resume_start, eliminating the hangs and restoring the stack-like
structure of the suspend/restore procedure.

Signed-off-by: Jakub Kądziołka <niedzejkob@invisiblethingslab.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220323012103.2537-1-niedzejkob@invisiblethingslab.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2022-03-25 14:22:15 -05:00

391 lines
8.3 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Handle extern requests for shutdown, reboot and sysrq
*/
#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/reboot.h>
#include <linux/sysrq.h>
#include <linux/stop_machine.h>
#include <linux/freezer.h>
#include <linux/syscore_ops.h>
#include <linux/export.h>
#include <xen/xen.h>
#include <xen/xenbus.h>
#include <xen/grant_table.h>
#include <xen/events.h>
#include <xen/hvc-console.h>
#include <xen/page.h>
#include <xen/xen-ops.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>
enum shutdown_state {
SHUTDOWN_INVALID = -1,
SHUTDOWN_POWEROFF = 0,
SHUTDOWN_SUSPEND = 2,
/* Code 3 is SHUTDOWN_CRASH, which we don't use because the domain can only
report a crash, not be instructed to crash!
HALT is the same as POWEROFF, as far as we're concerned. The tools use
the distinction when we return the reason code to them. */
SHUTDOWN_HALT = 4,
};
/* Ignore multiple shutdown requests. */
static enum shutdown_state shutting_down = SHUTDOWN_INVALID;
struct suspend_info {
int cancelled;
};
static RAW_NOTIFIER_HEAD(xen_resume_notifier);
void xen_resume_notifier_register(struct notifier_block *nb)
{
raw_notifier_chain_register(&xen_resume_notifier, nb);
}
EXPORT_SYMBOL_GPL(xen_resume_notifier_register);
void xen_resume_notifier_unregister(struct notifier_block *nb)
{
raw_notifier_chain_unregister(&xen_resume_notifier, nb);
}
EXPORT_SYMBOL_GPL(xen_resume_notifier_unregister);
#ifdef CONFIG_HIBERNATE_CALLBACKS
static int xen_suspend(void *data)
{
struct suspend_info *si = data;
int err;
BUG_ON(!irqs_disabled());
err = syscore_suspend();
if (err) {
pr_err("%s: system core suspend failed: %d\n", __func__, err);
return err;
}
gnttab_suspend();
xen_manage_runstate_time(-1);
xen_arch_pre_suspend();
si->cancelled = HYPERVISOR_suspend(xen_pv_domain()
? virt_to_gfn(xen_start_info)
: 0);
xen_arch_post_suspend(si->cancelled);
xen_manage_runstate_time(si->cancelled ? 1 : 0);
gnttab_resume();
if (!si->cancelled) {
xen_irq_resume();
xen_timer_resume();
}
syscore_resume();
return 0;
}
static void do_suspend(void)
{
int err;
struct suspend_info si;
shutting_down = SHUTDOWN_SUSPEND;
err = freeze_processes();
if (err) {
pr_err("%s: freeze processes failed %d\n", __func__, err);
goto out;
}
err = freeze_kernel_threads();
if (err) {
pr_err("%s: freeze kernel threads failed %d\n", __func__, err);
goto out_thaw;
}
err = dpm_suspend_start(PMSG_FREEZE);
if (err) {
pr_err("%s: dpm_suspend_start %d\n", __func__, err);
goto out_thaw;
}
printk(KERN_DEBUG "suspending xenstore...\n");
xs_suspend();
err = dpm_suspend_end(PMSG_FREEZE);
if (err) {
pr_err("dpm_suspend_end failed: %d\n", err);
si.cancelled = 0;
goto out_resume;
}
xen_arch_suspend();
si.cancelled = 1;
err = stop_machine(xen_suspend, &si, cpumask_of(0));
/* Resume console as early as possible. */
if (!si.cancelled)
xen_console_resume();
raw_notifier_call_chain(&xen_resume_notifier, 0, NULL);
xen_arch_resume();
dpm_resume_start(si.cancelled ? PMSG_THAW : PMSG_RESTORE);
if (err) {
pr_err("failed to start xen_suspend: %d\n", err);
si.cancelled = 1;
}
out_resume:
if (!si.cancelled)
xs_resume();
else
xs_suspend_cancel();
dpm_resume_end(si.cancelled ? PMSG_THAW : PMSG_RESTORE);
out_thaw:
thaw_processes();
out:
shutting_down = SHUTDOWN_INVALID;
}
#endif /* CONFIG_HIBERNATE_CALLBACKS */
struct shutdown_handler {
#define SHUTDOWN_CMD_SIZE 11
const char command[SHUTDOWN_CMD_SIZE];
bool flag;
void (*cb)(void);
};
static int poweroff_nb(struct notifier_block *cb, unsigned long code, void *unused)
{
switch (code) {
case SYS_DOWN:
case SYS_HALT:
case SYS_POWER_OFF:
shutting_down = SHUTDOWN_POWEROFF;
break;
default:
break;
}
return NOTIFY_DONE;
}
static void do_poweroff(void)
{
switch (system_state) {
case SYSTEM_BOOTING:
case SYSTEM_SCHEDULING:
orderly_poweroff(true);
break;
case SYSTEM_RUNNING:
orderly_poweroff(false);
break;
default:
/* Don't do it when we are halting/rebooting. */
pr_info("Ignoring Xen toolstack shutdown.\n");
break;
}
}
static void do_reboot(void)
{
shutting_down = SHUTDOWN_POWEROFF; /* ? */
ctrl_alt_del();
}
static struct shutdown_handler shutdown_handlers[] = {
{ "poweroff", true, do_poweroff },
{ "halt", false, do_poweroff },
{ "reboot", true, do_reboot },
#ifdef CONFIG_HIBERNATE_CALLBACKS
{ "suspend", true, do_suspend },
#endif
};
static void shutdown_handler(struct xenbus_watch *watch,
const char *path, const char *token)
{
char *str;
struct xenbus_transaction xbt;
int err;
int idx;
if (shutting_down != SHUTDOWN_INVALID)
return;
again:
err = xenbus_transaction_start(&xbt);
if (err)
return;
str = (char *)xenbus_read(xbt, "control", "shutdown", NULL);
/* Ignore read errors and empty reads. */
if (XENBUS_IS_ERR_READ(str)) {
xenbus_transaction_end(xbt, 1);
return;
}
for (idx = 0; idx < ARRAY_SIZE(shutdown_handlers); idx++) {
if (strcmp(str, shutdown_handlers[idx].command) == 0)
break;
}
/* Only acknowledge commands which we are prepared to handle. */
if (idx < ARRAY_SIZE(shutdown_handlers))
xenbus_write(xbt, "control", "shutdown", "");
err = xenbus_transaction_end(xbt, 0);
if (err == -EAGAIN) {
kfree(str);
goto again;
}
if (idx < ARRAY_SIZE(shutdown_handlers)) {
shutdown_handlers[idx].cb();
} else {
pr_info("Ignoring shutdown request: %s\n", str);
shutting_down = SHUTDOWN_INVALID;
}
kfree(str);
}
#ifdef CONFIG_MAGIC_SYSRQ
static void sysrq_handler(struct xenbus_watch *watch, const char *path,
const char *token)
{
char sysrq_key = '\0';
struct xenbus_transaction xbt;
int err;
again:
err = xenbus_transaction_start(&xbt);
if (err)
return;
err = xenbus_scanf(xbt, "control", "sysrq", "%c", &sysrq_key);
if (err < 0) {
/*
* The Xenstore watch fires directly after registering it and
* after a suspend/resume cycle. So ENOENT is no error but
* might happen in those cases. ERANGE is observed when we get
* an empty value (''), this happens when we acknowledge the
* request by writing '\0' below.
*/
if (err != -ENOENT && err != -ERANGE)
pr_err("Error %d reading sysrq code in control/sysrq\n",
err);
xenbus_transaction_end(xbt, 1);
return;
}
if (sysrq_key != '\0') {
err = xenbus_printf(xbt, "control", "sysrq", "%c", '\0');
if (err) {
pr_err("%s: Error %d writing sysrq in control/sysrq\n",
__func__, err);
xenbus_transaction_end(xbt, 1);
return;
}
}
err = xenbus_transaction_end(xbt, 0);
if (err == -EAGAIN)
goto again;
if (sysrq_key != '\0')
handle_sysrq(sysrq_key);
}
static struct xenbus_watch sysrq_watch = {
.node = "control/sysrq",
.callback = sysrq_handler
};
#endif
static struct xenbus_watch shutdown_watch = {
.node = "control/shutdown",
.callback = shutdown_handler
};
static struct notifier_block xen_reboot_nb = {
.notifier_call = poweroff_nb,
};
static int setup_shutdown_watcher(void)
{
int err;
int idx;
#define FEATURE_PATH_SIZE (SHUTDOWN_CMD_SIZE + sizeof("feature-"))
char node[FEATURE_PATH_SIZE];
err = register_xenbus_watch(&shutdown_watch);
if (err) {
pr_err("Failed to set shutdown watcher\n");
return err;
}
#ifdef CONFIG_MAGIC_SYSRQ
err = register_xenbus_watch(&sysrq_watch);
if (err) {
pr_err("Failed to set sysrq watcher\n");
return err;
}
#endif
for (idx = 0; idx < ARRAY_SIZE(shutdown_handlers); idx++) {
if (!shutdown_handlers[idx].flag)
continue;
snprintf(node, FEATURE_PATH_SIZE, "feature-%s",
shutdown_handlers[idx].command);
err = xenbus_printf(XBT_NIL, "control", node, "%u", 1);
if (err) {
pr_err("%s: Error %d writing %s\n", __func__,
err, node);
return err;
}
}
return 0;
}
static int shutdown_event(struct notifier_block *notifier,
unsigned long event,
void *data)
{
setup_shutdown_watcher();
return NOTIFY_DONE;
}
int xen_setup_shutdown_event(void)
{
static struct notifier_block xenstore_notifier = {
.notifier_call = shutdown_event
};
if (!xen_domain())
return -ENODEV;
register_xenstore_notifier(&xenstore_notifier);
register_reboot_notifier(&xen_reboot_nb);
return 0;
}
EXPORT_SYMBOL_GPL(xen_setup_shutdown_event);
subsys_initcall(xen_setup_shutdown_event);