On 04/07/2017 11:25, Christian Borntraeger wrote:
> On 07/04/2017 11:23 AM, Paolo Bonzini wrote:
>>
>>
>> On 04/07/2017 11:03, Claudio Imbrenda wrote:
>>> This patch adds a few lines to the KVM common code to fire a
>>> KOBJ_CHANGE uevent whenever a KVM VM is created or destroyed. The event
>>> carries two environment variables:
>>> KVM_VM_CREATED which indicates how many times a new VM has been created,
>>> KVM_VM_COUNT which indicates how many VMs are currently active.
>>
>> I'm not sure why KVM_VM_CREATED is useful, KVM_VM_COUNT can be a bit
>> more interesting though not much.
>
> I am certainly interested in an trigger from "kvm was never used" to "kvm was used",
> so having something like KVM_VM_CREATED has a value for me.
Fair enough, that's a good use. Please add it to the commit message,
however.
Paolo
>> But since we are at it, let's also add a PID. That one is the really
>> useful one, because it gives you something to look at in debugfs.
>> Another possibility is to add the debugfs directory name directly
>> (KVM_VM_STATS_PATH or something like that).
>>
>> Paolo
>>
>>> Specific udev rules can be then set up in userspace to deal with the
>>> creation or destruction of VMs as needed.
>>>
>>> Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxxxxxxx>
>>> ---
>>> virt/kvm/kvm_main.c | 25 +++++++++++++++++++++++++
>>> 1 file changed, 25 insertions(+)
>>>
>>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>>> index 6e3b12c..f67aa59 100644
>>> --- a/virt/kvm/kvm_main.c
>>> +++ b/virt/kvm/kvm_main.c
>>> @@ -130,6 +130,10 @@ EXPORT_SYMBOL_GPL(kvm_rebooting);
>>>
>>> static bool largepages_enabled = true;
>>>
>>> +static void kvm_uevent_notify_change(u64 created, u64 active);
>>> +static u64 kvm_createvm_count;
>>> +static u64 kvm_active_vms;
>>> +
>>> bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
>>> {
>>> if (pfn_valid(pfn))
>>> @@ -627,6 +631,7 @@ static struct kvm *kvm_create_vm(unsigned long type)
>>> {
>>> int r, i;
>>> struct kvm *kvm = kvm_arch_alloc_vm();
>>> + u64 activevms, createdvms;
>>>
>>> if (!kvm)
>>> return ERR_PTR(-ENOMEM);
>>> @@ -686,9 +691,12 @@ static struct kvm *kvm_create_vm(unsigned long type)
>>>
>>> spin_lock(&kvm_lock);
>>> list_add(&kvm->vm_list, &vm_list);
>>> + createdvms = ++kvm_createvm_count;
>>> + activevms = ++kvm_active_vms;
>>> spin_unlock(&kvm_lock);
>>>
>>> preempt_notifier_inc();
>>> + kvm_uevent_notify_change(createdvms, activevms);
>>>
>>> return kvm;
>>>
>>> @@ -739,11 +747,14 @@ static void kvm_destroy_vm(struct kvm *kvm)
>>> {
>>> int i;
>>> struct mm_struct *mm = kvm->mm;
>>> + u64 activevms, createdvms;
>>>
>>> kvm_destroy_vm_debugfs(kvm);
>>> kvm_arch_sync_events(kvm);
>>> spin_lock(&kvm_lock);
>>> list_del(&kvm->vm_list);
>>> + activevms = --kvm_active_vms;
>>> + createdvms = kvm_createvm_count;
>>> spin_unlock(&kvm_lock);
>>> kvm_free_irq_routing(kvm);
>>> for (i = 0; i < KVM_NR_BUSES; i++) {
>>> @@ -767,6 +778,7 @@ static void kvm_destroy_vm(struct kvm *kvm)
>>> preempt_notifier_dec();
>>> hardware_disable_all();
>>> mmdrop(mm);
>>> + kvm_uevent_notify_change(createdvms, activevms);
>>> }
>>>
>>> void kvm_get_kvm(struct kvm *kvm)
>>> @@ -3864,6 +3876,19 @@ static const struct file_operations *stat_fops[] = {
>>> [KVM_STAT_VM] = &vm_stat_fops,
>>> };
>>>
>>> +static void kvm_uevent_notify_change(u64 created, u64 active)
>>> +{
>>> + char createvm_buf[40];
>>> + char activevm_buf[40];
>>> + char *ptr[3] = {createvm_buf, activevm_buf, NULL};
>>> +
>>> + if (!kvm_dev.this_device)
>>> + return;
>>> + snprintf(createvm_buf, 40, "KVM_VM_CREATED=%llu", created);
>>> + snprintf(activevm_buf, 40, "KVM_VM_ACTIVE=%llu", active);
>>> + kobject_uevent_env(&kvm_dev.this_device->kobj, KOBJ_CHANGE, ptr);
>>> +}
>>> +
>>> static int kvm_init_debug(void)
>>> {
>>> int r = -EEXIST;
>>>
>>
>
