RE: [PATCH] vhost: add runtime locking check in unsafe APIs

["Hu, Jiayu" <jiayu.hu@intel.com>]

Hi Maxime,

This is a good idea to add the lock check below. But I have two
questions:
First, rte_vhost_clear_queue_thread_unsafe() is thread unsafe.
Why doesn't add the check for it?
Second, dev->notify_ops->destroy_device() is called without taking
the lock. If vhost applications try to clear inflight packets or even
unregister asynchronous data-path in this callback, rather than in
dev->notify_ops->vring_state_changed(), asynchronous APIs below
will return -1. How to handle this situation?

Thanks,
Jiayu

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Tuesday, May 10, 2022 4:25 PM
> To: dev@dpdk.org; Xia, Chenbo <chenbo.xia@intel.com>; Ding, Xuan
> <xuan.ding@intel.com>; Hu, Jiayu <jiayu.hu@intel.com>; Jiang, Cheng1
> <cheng1.jiang@intel.com>; Pai G, Sunil <sunil.pai.g@intel.com>;
> david.marchand@redhat.com
> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
> Subject: [PATCH] vhost: add runtime locking check in unsafe APIs
> 
> This patch adds runtime checks in unsafe Vhost async APIs, to ensure the
> access lock is taken.
> 
> The detection won't work every time, as another thread could take the lock,
> but it would help to detect misuse of these unsafe API.
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  lib/vhost/vhost.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c index
> df0bb9d043..39cbeb415c 100644
> --- a/lib/vhost/vhost.c
> +++ b/lib/vhost/vhost.c
> @@ -1732,6 +1732,12 @@
> rte_vhost_async_channel_register_thread_unsafe(int vid, uint16_t queue_id)
>  	if (unlikely(vq == NULL || !dev->async_copy))
>  		return -1;
> 
> +	if (unlikely(!rte_spinlock_is_locked(&vq->access_lock))) {
> +		VHOST_LOG_CONFIG(ERR, "(%s) %s() called without access
> lock taken.\n",
> +				dev->ifname, __func__);
> +		return -1;
> +	}
> +
>  	return async_channel_register(vid, queue_id);  }
> 
> @@ -1796,6 +1802,12 @@
> rte_vhost_async_channel_unregister_thread_unsafe(int vid, uint16_t
> queue_id)
>  	if (vq == NULL)
>  		return -1;
> 
> +	if (unlikely(!rte_spinlock_is_locked(&vq->access_lock))) {
> +		VHOST_LOG_CONFIG(ERR, "(%s) %s() called without access
> lock taken.\n",
> +				dev->ifname, __func__);
> +		return -1;
> +	}
> +
>  	if (!vq->async)
>  		return 0;
> 
> @@ -1925,6 +1937,12 @@ rte_vhost_async_get_inflight_thread_unsafe(int
> vid, uint16_t queue_id)
>  	if (vq == NULL)
>  		return ret;
> 
> +	if (unlikely(!rte_spinlock_is_locked(&vq->access_lock))) {
> +		VHOST_LOG_CONFIG(ERR, "(%s) %s() called without access
> lock taken.\n",
> +				dev->ifname, __func__);
> +		return -1;
> +	}
> +
>  	if (!vq->async)
>  		return ret;
> 
> --
> 2.35.1