On Tue, 4 Jul 2017 11:27:44 +0200
Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> 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.
I'll add that too
> 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;
> >>>
> >>
> >
>
