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.
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;
>
