| Message ID | 1499875004-17113-2-git-send-email-imbrenda@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
> + add_uevent_var(env, "CREATED=%llu", created); > + add_uevent_var(env, "COUNT=%llu", active); I like that much better. > + > + 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]; I'd move this also to the top of the function. Or move tmp and pathbuf in here, so you could also move them to this place. > + > + snprintf(p, sizeof(p), "%s", kvm->debugfs_dentry->d_name.name); Probably just me, but I prefer ARRAY_SIZE() instead of sizeof() for any kind of array sizes. > + 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="; Can't you avoid that? See next paragraph. > + > + tmp = dentry_path_raw(kvm->debugfs_dentry, > + pathbuf + len, > + PATH_MAX - len); > + if (!IS_ERR(tmp)) { Why not tmp = dentry_path_raw(kvm->debugfs_dentry, pathbuf, PATH_MAX); if (!IS_ERR(tmp)) { add_uevent_var(env, "STATS_PATH=s", tmp); } and avoid len / pvar / memcpy? And keep internal env size checking consistent. (are my tired eyes missing something? :) ) > + 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; >
On Mon, 17 Jul 2017 17:53:51 +0200 David Hildenbrand <david@redhat.com> wrote: > > + add_uevent_var(env, "CREATED=%llu", created); > > + add_uevent_var(env, "COUNT=%llu", active); > > I like that much better. > > > + > > + 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]; > > I'd move this also to the top of the function. Or move tmp and pathbuf > in here, so you could also move them to this place. yeah it would probably look cleaner, I'll fix it. > > + > > + snprintf(p, sizeof(p), "%s", > > kvm->debugfs_dentry->d_name.name); > > Probably just me, but I prefer ARRAY_SIZE() instead of sizeof() for > any kind of array sizes. I'll fix that too > > + 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="; > > Can't you avoid that? See next paragraph. > > > > + > > + tmp = dentry_path_raw(kvm->debugfs_dentry, > > + pathbuf + len, > > + PATH_MAX - len); > > + if (!IS_ERR(tmp)) { > > Why not > > tmp = dentry_path_raw(kvm->debugfs_dentry, pathbuf, PATH_MAX); > if (!IS_ERR(tmp)) { > add_uevent_var(env, "STATS_PATH=s", tmp); > } > > and avoid len / pvar / memcpy? And keep internal env size checking > consistent. that would be true, but then we would copy the buffer with the path twice, once for dentry_path_raw and once for add_uevent_var. the env size is consistent, since that would count the bytes effectively present in the buffer, and note that kobject_uevent_env only wants a char**, no length, so there are no consistency issues. I agree that your solution looks better (and I had actually considered implementing it like that initially), but it can potentially be slower. I don't really have any strong preference. Paolo: which solution do you like the most? [...]
2017-07-17 18:27+0200, Claudio Imbrenda: > On Mon, 17 Jul 2017 17:53:51 +0200 > David Hildenbrand <david@redhat.com> wrote: > > > + tmp = strchrnul(p + 1, '-');> + > > > *tmp = '\0'; > > > + add_uevent_var(env, "PID=%s", p); When we're at it ... PID exists regardless of debugfs, so it would be nice to provide it unconditionally. (This interface looks like it was added to discourage the use of debugfs directory notifier in simple cases.) I guess we cannot use task_pid_nr(current) on the KVM_EVENT_DESTROY_VM path, so saving the PID in struct kvm would be better, IMO (it wastes memory with larger number of VMs, but the code is harder to break). > > > + tmp = dentry_path_raw(kvm->debugfs_dentry, > > > + pathbuf + len, > > > + PATH_MAX - len); > > > + if (!IS_ERR(tmp)) { > > > > Why not > > > > tmp = dentry_path_raw(kvm->debugfs_dentry, pathbuf, PATH_MAX); > > if (!IS_ERR(tmp)) { > > add_uevent_var(env, "STATS_PATH=s", tmp); > > } > > > > and avoid len / pvar / memcpy? And keep internal env size checking > > consistent. > > that would be true, but then we would copy the buffer with the path > twice, once for dentry_path_raw and once for add_uevent_var. > > the env size is consistent, since that would count the bytes > effectively present in the buffer, and note that kobject_uevent_env only > wants a char**, no length, so there are no consistency issues. > > I agree that your solution looks better (and I had actually considered > implementing it like that initially), but it can potentially be slower. > I don't really have any strong preference. > > Paolo: which solution do you like the most? I slightly prefer the simpler version as performance of the path is not that critical. Please note that the original patch is already in 4.13 (it was ok and my nitpicking would just make it miss the merge window :]), so the code improvements need to be a new patch, thanks.
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index f0fe9d0..24ad3f5 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)) @@ -728,6 +734,7 @@ 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); @@ -3196,6 +3203,7 @@ 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; @@ -3848,6 +3856,67 @@ 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;
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 <imbrenda@linux.vnet.ibm.com> --- virt/kvm/kvm_main.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+)