[PATCH] KVM breaks CPU hotplug

Shaohua Li
2007-03-26T08:48:13Z

When testing CPU hotplug, I found cpu can't be onlined with kvm enabled
sometimes. The reason is smp_call_function_single is a nop if the thread
is running on the target cpu. I think CPU_ONLINE case doesn't require
the fix as the online CPU isn't plugged into sheduler yet.

Signed-off-by: Shaohua Li <shaohua.li-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index dc7a8c7..806a931 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -2360,6 +2360,7 @@ static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
void *v)
{
int cpu = (long)v;
+ int this_cpu;

switch (val) {
case CPU_DOWN_PREPARE:
@@ -2367,8 +2368,13 @@ static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
printk(KERN_INFO "kvm: disabling virtualization on CPU%d\n",
cpu);
decache_vcpus_on_cpu(cpu);
- smp_call_function_single(cpu, kvm_arch_ops->hardware_disable,
- NULL, 0, 1);
+ this_cpu = get_cpu();
+ if (this_cpu == cpu)
+ kvm_arch_ops->hardware_disable(NULL);
+ else
+ smp_call_function_single(cpu,
+ kvm_arch_ops->hardware_disable, NULL, 0, 1);
+ put_cpu();
break;
case CPU_ONLINE:
printk(KERN_INFO "kvm: enabling virtualization on CPU%d\n",