linux-kernel - Re: [PATCH v2 1/1] KVM: make pid available for uevents without debugfs

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Date:   Mon, 24 Jul 2017 16:30:27 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Claudio Imbrenda <imbrenda@...ux.vnet.ibm.com>, kvm@...r.kernel.org
Cc:     borntraeger@...ibm.com, linux-kernel@...r.kernel.org,
        rkrcmar@...hat.com
Subject: Re: [PATCH v2 1/1] KVM: make pid available for uevents without
 debugfs

On 24/07/2017 13:40, Claudio Imbrenda wrote:
> Simplify and improve the code so that the PID is always available in
> the uevent even when debugfs is not available.
> 
> This adds a userspace_pid field to struct kvm, as per Radim's
> suggestion, so that the PID can be retrieved on destruction too.
> 
> Acked-by: Janosch Frank <frankja@...ux.vnet.ibm.com>
> Fixes: 286de8f6ac9202 ("KVM: trigger uevents when creating or destroying a VM")
> Signed-off-by: Claudio Imbrenda <imbrenda@...ux.vnet.ibm.com>
> ---
>  include/linux/kvm_host.h |  1 +
>  virt/kvm/kvm_main.c      | 35 ++++++++++++-----------------------
>  2 files changed, 13 insertions(+), 23 deletions(-)
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 648b34c..890b706 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -445,6 +445,7 @@ struct kvm {
>  	struct kvm_stat_data **debugfs_stat_data;
>  	struct srcu_struct srcu;
>  	struct srcu_struct irq_srcu;
> +	pid_t userspace_pid;
>  };
>  
>  #define kvm_err(fmt, ...) \
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 82987d4..f3f7427 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -3883,7 +3883,6 @@ static const struct file_operations *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)
> @@ -3907,38 +3906,28 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm)
>  	add_uevent_var(env, "CREATED=%llu", created);
>  	add_uevent_var(env, "COUNT=%llu", active);
>  
> -	if (type == KVM_EVENT_CREATE_VM)
> +	if (type == KVM_EVENT_CREATE_VM) {
>  		add_uevent_var(env, "EVENT=create");
> -	else if (type == KVM_EVENT_DESTROY_VM)
> +		kvm->userspace_pid = task_pid_nr(current);
> +	} else if (type == KVM_EVENT_DESTROY_VM) {
>  		add_uevent_var(env, "EVENT=destroy");
> +	}
> +	add_uevent_var(env, "PID=%d", kvm->userspace_pid);
>  
>  	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;
> -			}
> +		char *tmp, *p = kmalloc(PATH_MAX, GFP_KERNEL);
> +
> +		if (p) {
> +			tmp = dentry_path_raw(kvm->debugfs_dentry, p, PATH_MAX);
> +			if (!IS_ERR(tmp))
> +				add_uevent_var(env, "STATS_PATH=%s", tmp);
> +			kfree(p);
>  		}
>  	}
>  	/* 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)
> 

Looks good, thanks.

Paolo