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.
>
> 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 <imbre...@linux.vnet.ibm.com>
>> ---
>> 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;
>>
>
