From 286de8f6ac9202f1c9012784639156c6ec386eb8 Mon Sep 17 00:00:00 2001 From: Claudio Imbrenda Date: Wed, 12 Jul 2017 17:56:44 +0200 Subject: [PATCH] KVM: trigger uevents when creating or destroying a VM MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 five environment variables: CREATED indicates how many times a new VM has been created. It is useful for example to trigger specific actions when the first VM is started COUNT indicates how many VMs are currently active. This can be used for logging or monitoring purposes PID has the pid of the KVM process that has been started or stopped. This can be used to perform process-specific tuning. STATS_PATH contains the path in debugfs to the directory with all the runtime statistics for this VM. This is useful for performance monitoring and profiling. EVENT described the type of event, its value can be either "create" or "destroy" 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 Signed-off-by: Radim Krčmář --- virt/kvm/kvm_main.c | 69 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 7766c2b52797..82987d457b8b 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -130,6 +130,12 @@ EXPORT_SYMBOL_GPL(kvm_rebooting); static bool largepages_enabled = true; +#define KVM_EVENT_CREATE_VM 0 +#define KVM_EVENT_DESTROY_VM 1 +static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm); +static unsigned long long kvm_createvm_count; +static unsigned long long kvm_active_vms; + bool kvm_is_reserved_pfn(kvm_pfn_t pfn) { if (pfn_valid(pfn)) @@ -740,6 +746,7 @@ static void kvm_destroy_vm(struct kvm *kvm) int i; struct mm_struct *mm = kvm->mm; + kvm_uevent_notify_change(KVM_EVENT_DESTROY_VM, kvm); kvm_destroy_vm_debugfs(kvm); kvm_arch_sync_events(kvm); spin_lock(&kvm_lock); @@ -3220,6 +3227,7 @@ static int kvm_dev_ioctl_create_vm(unsigned long type) fput(file); return -ENOMEM; } + kvm_uevent_notify_change(KVM_EVENT_CREATE_VM, kvm); fd_install(r, file); return r; @@ -3872,6 +3880,67 @@ static const struct file_operations *stat_fops[] = { [KVM_STAT_VM] = &vm_stat_fops, }; +static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm) +{ + struct kobj_uevent_env *env; + char *tmp, *pathbuf = NULL; + unsigned long long created, active; + + if (!kvm_dev.this_device || !kvm) + return; + + spin_lock(&kvm_lock); + if (type == KVM_EVENT_CREATE_VM) { + kvm_createvm_count++; + kvm_active_vms++; + } else if (type == KVM_EVENT_DESTROY_VM) { + kvm_active_vms--; + } + created = kvm_createvm_count; + active = kvm_active_vms; + spin_unlock(&kvm_lock); + + env = kzalloc(sizeof(*env), GFP_KERNEL); + if (!env) + return; + + add_uevent_var(env, "CREATED=%llu", created); + add_uevent_var(env, "COUNT=%llu", active); + + if (type == KVM_EVENT_CREATE_VM) + add_uevent_var(env, "EVENT=create"); + else if (type == KVM_EVENT_DESTROY_VM) + add_uevent_var(env, "EVENT=destroy"); + + if (kvm->debugfs_dentry) { + char p[ITOA_MAX_LEN]; + + snprintf(p, sizeof(p), "%s", kvm->debugfs_dentry->d_name.name); + tmp = strchrnul(p + 1, '-'); + *tmp = '\0'; + add_uevent_var(env, "PID=%s", p); + pathbuf = kmalloc(PATH_MAX, GFP_KERNEL); + if (pathbuf) { + /* sizeof counts the final '\0' */ + int len = sizeof("STATS_PATH=") - 1; + const char *pvar = "STATS_PATH="; + + tmp = dentry_path_raw(kvm->debugfs_dentry, + pathbuf + len, + PATH_MAX - len); + if (!IS_ERR(tmp)) { + memcpy(tmp - len, pvar, len); + env->envp[env->envp_idx++] = tmp - len; + } + } + } + /* no need for checks, since we are adding at most only 5 keys */ + env->envp[env->envp_idx++] = NULL; + kobject_uevent_env(&kvm_dev.this_device->kobj, KOBJ_CHANGE, env->envp); + kfree(env); + kfree(pathbuf); +} + static int kvm_init_debug(void) { int r = -EEXIST; -- 2.20.1