Avi Kivity wrote:
> On 06/15/2009 02:30 PM, Alexander Graf wrote:
>> X86 CPUs need to have some magic happening to enable the virtualization
>> extensions on them. This magic can result in unpleasant results for
>> users, like blocking other VMMs from working (vmx) or using invalid TLB
>> entries (svm).
>>
>> Currently KVM activates virtualization when the respective kernel module
>> is loaded. This blocks us from autoloading KVM modules without breaking
>> other VMMs.
>>
>> To circumvent this problem at least a bit, this patch introduces on
>> demand activation of virtualization. This means, that instead
>> virtualization is enabled on creation of the first virtual machine
>> and disabled on destruction of the last one.
>>
>> So using this, KVM can be easily autoloaded, while keeping other
>> hypervisors usable.
>>
>> +static int hardware_enable_all(void)
>> +{
>> + int r = 0;
>> +
>> + spin_lock(&kvm_lock);
>> +
>> + kvm_usage_count++;
>> + if (kvm_usage_count == 1) {
>> + atomic_set(&hardware_enable_failed, 1);
>> + on_each_cpu(hardware_enable, NULL, 1);
>> +
>> + if (!atomic_dec_and_test(&hardware_enable_failed))
>> + r = -EBUSY;
>> + }
>>
>
> That's a little obfuscated. I suggest atomic_set(..., p) and
> atomic_read(...).
Ah, I was more searching for an atomic_test :-).
>> static int kvm_cpu_hotplug(struct notifier_block *notifier,
>> unsigned long val,
>> void *v)
>> {
>> int cpu = (long)v;
>>
>> + if (!kvm_usage_count)
>> + return NOTIFY_OK;
>> +
>> val&= ~CPU_TASKS_FROZEN;
>> switch (val) {
>> case CPU_DYING:
>> @@ -2513,13 +2571,15 @@ static void kvm_exit_debug(void)
>>
>> static int kvm_suspend(struct sys_device *dev, pm_message_t state)
>> {
>> - hardware_disable(NULL);
>> + if (kvm_usage_count)
>> + hardware_disable(NULL);
>> return 0;
>> }
>>
>> static int kvm_resume(struct sys_device *dev)
>> {
>> - hardware_enable(NULL);
>> + if (kvm_usage_count)
>> + hardware_enable(NULL);
>> return 0;
>> }
>>
>>
> +
>
> Please tell me you tested suspend/resume with/without VMs and cpu
> hotunplug/hotplug.
I tested cpu hotplugging. On the last round I tested suspend/resume, but
this time I couldn't because my machine can't do suspend :-(.
So I'll try hard and find a machine I can test it on for the next round.
Alex
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