[PATCH 18/20] KVM: Keep track of which cpus have virtualization enabled

Avi Kivity
2007-07-08T11:54:47Z

By keeping track of which cpus have virtualization enabled, we
prevent double-enable or double-disable during hotplug, which is a
very fatal oops.

Signed-off-by: Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
---
drivers/kvm/kvm_main.c | 45 +++++++++++++++++++++++++++++++++------------
1 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index ea02719..3226ad4 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -50,8 +50,12 @@ MODULE_LICENSE("GPL");
static DEFINE_SPINLOCK(kvm_lock);
static LIST_HEAD(vm_list);

+static cpumask_t cpus_hardware_enabled;
+
struct kvm_arch_ops *kvm_arch_ops;

+static void hardware_disable(void *ignored);
+
#define STAT_OFFSET(x) offsetof(struct kvm_vcpu, stat.x)

static struct kvm_stats_debugfs_item {
@@ -2930,7 +2934,7 @@ static int kvm_reboot(struct notifier_block *notifier, unsigned long val,
* in vmx root mode.
*/
printk(KERN_INFO "kvm: exiting hardware virtualization\n");
- on_each_cpu(kvm_arch_ops->hardware_disable, NULL, 0, 1);
+ on_each_cpu(hardware_disable, NULL, 0, 1);
}
return NOTIFY_OK;
}
@@ -2973,6 +2977,27 @@ static void decache_vcpus_on_cpu(int cpu)
spin_unlock(&kvm_lock);
}

+static void hardware_enable(void *junk)
+{
+ int cpu = raw_smp_processor_id();
+
+ if (cpu_isset(cpu, cpus_hardware_enabled))
+ return;
+ cpu_set(cpu, cpus_hardware_enabled);
+ kvm_arch_ops->hardware_enable(NULL);
+}
+
+static void hardware_disable(void *junk)
+{
+ int cpu = raw_smp_processor_id();
+
+ if (!cpu_isset(cpu, cpus_hardware_enabled))
+ return;
+ cpu_clear(cpu, cpus_hardware_enabled);
+ decache_vcpus_on_cpu(cpu);
+ kvm_arch_ops->hardware_disable(NULL);
+}
+
static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
void *v)
{
@@ -2985,16 +3010,13 @@ static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
case CPU_UP_CANCELED_FROZEN:
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);
+ smp_call_function_single(cpu, hardware_disable, NULL, 0, 1);
break;
case CPU_ONLINE:
case CPU_ONLINE_FROZEN:
printk(KERN_INFO "kvm: enabling virtualization on CPU%d\n",
cpu);
- smp_call_function_single(cpu, kvm_arch_ops->hardware_enable,
- NULL, 0, 1);
+ smp_call_function_single(cpu, hardware_enable, NULL, 0, 1);
break;
}
return NOTIFY_OK;
@@ -3088,14 +3110,13 @@ static void kvm_exit_debug(void)

static int kvm_suspend(struct sys_device *dev, pm_message_t state)
{
- decache_vcpus_on_cpu(raw_smp_processor_id());
- on_each_cpu(kvm_arch_ops->hardware_disable, NULL, 0, 1);
+ on_each_cpu(hardware_disable, NULL, 0, 0);
return 0;
}

static int kvm_resume(struct sys_device *dev)
{
- on_each_cpu(kvm_arch_ops->hardware_enable, NULL, 0, 1);
+ on_each_cpu(hardware_disable, NULL, 0, 0);
return 0;
}

@@ -3136,7 +3157,7 @@ int kvm_init_arch(struct kvm_arch_ops *ops, struct module *module)
if (r < 0)
goto out;

- on_each_cpu(kvm_arch_ops->hardware_enable, NULL, 0, 1);
+ on_each_cpu(hardware_enable, NULL, 0, 1);
r = register_cpu_notifier(&kvm_cpu_notifier);
if (r)
goto out_free_1;
@@ -3168,7 +3189,7 @@ out_free_2:
unregister_reboot_notifier(&kvm_reboot_notifier);
unregister_cpu_notifier(&kvm_cpu_notifier);
out_free_1:
- on_each_cpu(kvm_arch_ops->hardware_disable, NULL, 0, 1);
+ on_each_cpu(hardware_disable, NULL, 0, 1);
kvm_arch_ops->hardware_unsetup();
out:
kvm_arch_ops = NULL;
@@ -3182,7 +3203,7 @@ void kvm_exit_arch(void)
sysdev_class_unregister(&kvm_sysdev_class);
unregister_reboot_notifier(&kvm_reboot_notifier);
unregister_cpu_notifier(&kvm_cpu_notifier);
- on_each_cpu(kvm_arch_ops->hardware_disable, NULL, 0, 1);
+ on_each_cpu(hardware_disable, NULL, 0, 1);
kvm_arch_ops->hardware_unsetup();
kvm_arch_ops = NULL;
}