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linux-next/drivers/xen/cpu_hotplug.c
Boris Ostrovsky c54b071c19 xen/cpuhotplug: Fix initial CPU offlining for PV(H) guests
Commit a926f81d2f ("xen/cpuhotplug: Replace cpu_up/down() with
device_online/offline()") replaced cpu_down() with device_offline()
call which requires that the CPU has been registered before. This
registration, however, happens later from topology_init() which
is called as subsys_initcall(). setup_vcpu_hotplug_event(), on the
other hand, is invoked earlier, during arch_initcall().

As result, booting a PV(H) guest with vcpus < maxvcpus causes a crash.

Move setup_vcpu_hotplug_event() (and therefore setup_cpu_watcher()) to
late_initcall(). In addition, instead of performing all offlining steps
in setup_cpu_watcher() simply call disable_hotplug_cpu().

Fixes: a926f81d2f (xen/cpuhotplug: Replace cpu_up/down() with device_online/offline()"
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/1588976923-3667-1-git-send-email-boris.ostrovsky@oracle.com
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2020-05-21 13:01:45 -05:00

122 lines
2.3 KiB
C

// SPDX-License-Identifier: GPL-2.0
#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
#include <linux/notifier.h>
#include <xen/xen.h>
#include <xen/xenbus.h>
#include <asm/xen/hypervisor.h>
#include <asm/cpu.h>
static void enable_hotplug_cpu(int cpu)
{
if (!cpu_present(cpu))
xen_arch_register_cpu(cpu);
set_cpu_present(cpu, true);
}
static void disable_hotplug_cpu(int cpu)
{
if (!cpu_is_hotpluggable(cpu))
return;
lock_device_hotplug();
if (cpu_online(cpu))
device_offline(get_cpu_device(cpu));
if (!cpu_online(cpu) && cpu_present(cpu)) {
xen_arch_unregister_cpu(cpu);
set_cpu_present(cpu, false);
}
unlock_device_hotplug();
}
static int vcpu_online(unsigned int cpu)
{
int err;
char dir[16], state[16];
sprintf(dir, "cpu/%u", cpu);
err = xenbus_scanf(XBT_NIL, dir, "availability", "%15s", state);
if (err != 1) {
if (!xen_initial_domain())
pr_err("Unable to read cpu state\n");
return err;
}
if (strcmp(state, "online") == 0)
return 1;
else if (strcmp(state, "offline") == 0)
return 0;
pr_err("unknown state(%s) on CPU%d\n", state, cpu);
return -EINVAL;
}
static void vcpu_hotplug(unsigned int cpu)
{
if (cpu >= nr_cpu_ids || !cpu_possible(cpu))
return;
switch (vcpu_online(cpu)) {
case 1:
enable_hotplug_cpu(cpu);
break;
case 0:
disable_hotplug_cpu(cpu);
break;
default:
break;
}
}
static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
const char *path, const char *token)
{
unsigned int cpu;
char *cpustr;
cpustr = strstr(path, "cpu/");
if (cpustr != NULL) {
sscanf(cpustr, "cpu/%u", &cpu);
vcpu_hotplug(cpu);
}
}
static int setup_cpu_watcher(struct notifier_block *notifier,
unsigned long event, void *data)
{
int cpu;
static struct xenbus_watch cpu_watch = {
.node = "cpu",
.callback = handle_vcpu_hotplug_event};
(void)register_xenbus_watch(&cpu_watch);
for_each_possible_cpu(cpu) {
if (vcpu_online(cpu) == 0)
disable_hotplug_cpu(cpu);
}
return NOTIFY_DONE;
}
static int __init setup_vcpu_hotplug_event(void)
{
static struct notifier_block xsn_cpu = {
.notifier_call = setup_cpu_watcher };
#ifdef CONFIG_X86
if (!xen_pv_domain() && !xen_pvh_domain())
#else
if (!xen_domain())
#endif
return -ENODEV;
register_xenstore_notifier(&xsn_cpu);
return 0;
}
late_initcall(setup_vcpu_hotplug_event);