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xen: honour VCPU availability on boot 

If a VM is booted with offline VCPUs then unplug them during boot. Determining
the availability of a VCPU requires access to XenStore which is not available
at the point smp_prepare_cpus() is called, therefore we bring up all VCPUS
initially and unplug the offline ones as soon as XenStore becomes available.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
This commit is contained in:
Ian Campbell 2009-04-02 13:24:28 +01:00 committed by Jeremy Fitzhardinge
parent 2b2a733447
commit d745562cc4
1 changed files with 30 additions and 10 deletions
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40
drivers/xen/cpu_hotplug.c
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@ -21,29 +21,41 @@ static void disable_hotplug_cpu(int cpu)
set_cpu_present(cpu, false);
}
static void vcpu_hotplug(unsigned int cpu)
static int vcpu_online(unsigned int cpu)
{
int err;
char dir[32], state[32];
if (!cpu_possible(cpu))
return;
sprintf(dir, "cpu/%u", cpu);
err = xenbus_scanf(XBT_NIL, dir, "availability", "%s", state);
if (err != 1) {
printk(KERN_ERR "XENBUS: Unable to read cpu state\n");
return;
return err;
}
if (strcmp(state, "online") == 0) {
if (strcmp(state, "online") == 0)
return 1;
else if (strcmp(state, "offline") == 0)
return 0;
printk(KERN_ERR "XENBUS: unknown state(%s) on CPU%d\n", state, cpu);
return -EINVAL;
}
static void vcpu_hotplug(unsigned int cpu)
{
if (!cpu_possible(cpu))
return;
switch (vcpu_online(cpu)) {
case 1:
enable_hotplug_cpu(cpu);
} else if (strcmp(state, "offline") == 0) {
break;
case 0:
(void)cpu_down(cpu);
disable_hotplug_cpu(cpu);
} else {
printk(KERN_ERR "XENBUS: unknown state(%s) on CPU%d\n",
state, cpu);
break;
default:
break;
}
}
@ -64,12 +76,20 @@ static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
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) {
(void)cpu_down(cpu);
cpu_clear(cpu, cpu_present_map);
}
}
return NOTIFY_DONE;
}