Mailing List Archive

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>
---
drivers/xen/cpu_hotplug.c | 40 ++++++++++++++++++++++++++++++----------
1 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c
index 974f56d..411cb1f 100644
--- a/drivers/xen/cpu_hotplug.c
+++ b/drivers/xen/cpu_hotplug.c
@@ -21,29 +21,41 @@ static void disable_hotplug_cpu(int cpu)
cpu_clear(cpu, cpu_present_map);
}

-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;
}

--
1.5.6.5


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