On Tue, 4 Jul 2017 11:23:36 +0200
Paolo Bonzini <pbonzini@xxxxxxxxxx> 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.
>
> 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).
I'll add those
> 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;
> >
>
