RE: [RFC PATCH v2 3/9] vhost: annotate virtqueue access lock

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

Hi David,

Please see replies inline.

> -----Original Message-----
> From: David Marchand <david.marchand@redhat.com>
> Sent: Wednesday, March 30, 2022 9:50 PM
> To: dev@dpdk.org
> Cc: maxime.coquelin@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>; Hu,
> Jiayu <jiayu.hu@intel.com>; Wang, YuanX <yuanx.wang@intel.com>; Ding,
> Xuan <xuan.ding@intel.com>
> Subject: [RFC PATCH v2 3/9] vhost: annotate virtqueue access lock
> 
> This change simply annotates existing paths of the code leading to
> manipulations of the vq->access_lock.
> 
> One small change is required: vhost_poll_enqueue_completed was getting a
> queue_id to get hold of the vq, while its callers already knew of the vq. For
> the annotation sake, vq is now directly passed.
> 
> vhost_user_lock_all_queue_pairs and vhost_user_unlock_all_queue_pairs
> are skipped since vq->access_lock are conditionally held.
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> ---
>  lib/vhost/vhost.h      |  2 ++
>  lib/vhost/vhost_user.c |  2 ++
>  lib/vhost/virtio_net.c | 16 ++++++++++++----
>  3 files changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h index
> a9edc271aa..158460b7d7 100644
> --- a/lib/vhost/vhost.h
> +++ b/lib/vhost/vhost.h
> @@ -834,6 +834,7 @@ vhost_need_event(uint16_t event_idx, uint16_t
> new_idx, uint16_t old)
> 
>  static __rte_always_inline void
>  vhost_vring_call_split(struct virtio_net *dev, struct vhost_virtqueue *vq)
> +	RTE_EXC_LOCK_REQUIRES(vq->access_lock)

vhost_vring_call_split() is called in rte_vhost_vring_call() too, but it doesn't
acquire vq->access_lock before calling vhost_vring_call_split().

>  {
>  	/* Flush used->idx update before we read avail->flags. */
>  	rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
> @@ -872,6 +873,7 @@ vhost_vring_call_split(struct virtio_net *dev, struct
> vhost_virtqueue *vq)
> 
>  static __rte_always_inline void
>  vhost_vring_call_packed(struct virtio_net *dev, struct vhost_virtqueue *vq)
> +	RTE_EXC_LOCK_REQUIRES(vq->access_lock)

Ditto.

>  {
>  	uint16_t old, new, off, off_wrap;
>  	bool signalled_used_valid, kick = false; diff --git
> a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c index
> 1d390677fa..87eaa2ab4a 100644
> --- a/lib/vhost/vhost_user.c
> +++ b/lib/vhost/vhost_user.c
> @@ -2909,6 +2909,7 @@ vhost_user_check_and_alloc_queue_pair(struct
> virtio_net *dev,
> 
>  static void
>  vhost_user_lock_all_queue_pairs(struct virtio_net *dev)
> +	RTE_NO_ANNOTATED_LOCK_CHECK
>  {
>  	unsigned int i = 0;
>  	unsigned int vq_num = 0;
> @@ -2926,6 +2927,7 @@ vhost_user_lock_all_queue_pairs(struct virtio_net
> *dev)
> 
>  static void
>  vhost_user_unlock_all_queue_pairs(struct virtio_net *dev)
> +	RTE_NO_ANNOTATED_LOCK_CHECK
>  {
>  	unsigned int i = 0;
>  	unsigned int vq_num = 0;
> diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c index
> 5f432b0d77..514ee00993 100644
> --- a/lib/vhost/virtio_net.c
> +++ b/lib/vhost/virtio_net.c
> @@ -1246,6 +1246,7 @@ vhost_enqueue_single_packed(struct virtio_net
> *dev,  static __rte_noinline uint32_t  virtio_dev_rx_split(struct virtio_net
> *dev, struct vhost_virtqueue *vq,
>  	struct rte_mbuf **pkts, uint32_t count)
> +	RTE_EXC_LOCK_REQUIRES(vq->access_lock)
>  {
>  	uint32_t pkt_idx = 0;
>  	uint16_t num_buffers;
> @@ -1441,6 +1442,7 @@ virtio_dev_rx_packed(struct virtio_net *dev,
>  		     struct vhost_virtqueue *__rte_restrict vq,
>  		     struct rte_mbuf **__rte_restrict pkts,
>  		     uint32_t count)
> +	RTE_EXC_LOCK_REQUIRES(vq->access_lock)
>  {
>  	uint32_t pkt_idx = 0;
> 
> @@ -1955,11 +1957,11 @@ write_back_completed_descs_packed(struct
> vhost_virtqueue *vq,  }
> 
>  static __rte_always_inline uint16_t
> -vhost_poll_enqueue_completed(struct virtio_net *dev, uint16_t queue_id,
> +vhost_poll_enqueue_completed(struct virtio_net *dev, struct
> +vhost_virtqueue *vq,
>  		struct rte_mbuf **pkts, uint16_t count, int16_t dma_id,
>  		uint16_t vchan_id)
> +	RTE_EXC_LOCK_REQUIRES(vq->access_lock)

rte_vhost_clear_queue_thread_unsafe() doesn't acquire vq->access_lock.
Will it cause a compiler warning?

Thanks,
Jiayu
>  {
> -	struct vhost_virtqueue *vq = dev->virtqueue[queue_id];
>  	struct vhost_async *async = vq->async;
>  	struct async_inflight_info *pkts_info = async->pkts_info;
>  	uint16_t nr_cpl_pkts = 0;
> @@ -2062,7 +2064,7 @@ rte_vhost_poll_enqueue_completed(int vid,
> uint16_t queue_id,
>  		goto out;
>  	}
> 
> -	n_pkts_cpl = vhost_poll_enqueue_completed(dev, queue_id, pkts,
> count, dma_id, vchan_id);
> +	n_pkts_cpl = vhost_poll_enqueue_completed(dev, vq, pkts, count,
> +dma_id, vchan_id);
> 
>  out:
>  	rte_spinlock_unlock(&vq->access_lock);
> @@ -2104,7 +2106,7 @@ rte_vhost_clear_queue_thread_unsafe(int vid,
> uint16_t queue_id,
>  		return 0;
>  	}
> 
> -	n_pkts_cpl = vhost_poll_enqueue_completed(dev, queue_id, pkts,
> count, dma_id, vchan_id);
> +	n_pkts_cpl = vhost_poll_enqueue_completed(dev, vq, pkts, count,
> +dma_id, vchan_id);
> 
>  	return n_pkts_cpl;
>  }
> @@ -2679,6 +2681,7 @@ static uint16_t
>  virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
>  	struct rte_mempool *mbuf_pool, struct rte_mbuf **pkts, uint16_t
> count,
>  	bool legacy_ol_flags)
> +	RTE_EXC_LOCK_REQUIRES(vq->access_lock)
>  {
>  	uint16_t i;
>  	uint16_t free_entries;
> @@ -2774,6 +2777,7 @@ static uint16_t
>  virtio_dev_tx_split_legacy(struct virtio_net *dev,
>  	struct vhost_virtqueue *vq, struct rte_mempool *mbuf_pool,
>  	struct rte_mbuf **pkts, uint16_t count)
> +	RTE_EXC_LOCK_REQUIRES(vq->access_lock)
>  {
>  	return virtio_dev_tx_split(dev, vq, mbuf_pool, pkts, count, true);  }
> @@ -2783,6 +2787,7 @@ static uint16_t
> virtio_dev_tx_split_compliant(struct virtio_net *dev,
>  	struct vhost_virtqueue *vq, struct rte_mempool *mbuf_pool,
>  	struct rte_mbuf **pkts, uint16_t count)
> +	RTE_EXC_LOCK_REQUIRES(vq->access_lock)
>  {
>  	return virtio_dev_tx_split(dev, vq, mbuf_pool, pkts, count, false);  }
> @@ -2982,6 +2987,7 @@ virtio_dev_tx_packed(struct virtio_net *dev,
>  		     struct rte_mbuf **__rte_restrict pkts,
>  		     uint32_t count,
>  		     bool legacy_ol_flags)
> +	RTE_EXC_LOCK_REQUIRES(vq->access_lock)
>  {
>  	uint32_t pkt_idx = 0;
> 
> @@ -3025,6 +3031,7 @@ static uint16_t
>  virtio_dev_tx_packed_legacy(struct virtio_net *dev,
>  	struct vhost_virtqueue *__rte_restrict vq, struct rte_mempool
> *mbuf_pool,
>  	struct rte_mbuf **__rte_restrict pkts, uint32_t count)
> +	RTE_EXC_LOCK_REQUIRES(vq->access_lock)
>  {
>  	return virtio_dev_tx_packed(dev, vq, mbuf_pool, pkts, count, true);  }
> @@ -3034,6 +3041,7 @@ static uint16_t
> virtio_dev_tx_packed_compliant(struct virtio_net *dev,
>  	struct vhost_virtqueue *__rte_restrict vq, struct rte_mempool
> *mbuf_pool,
>  	struct rte_mbuf **__rte_restrict pkts, uint32_t count)
> +	RTE_EXC_LOCK_REQUIRES(vq->access_lock)
>  {
>  	return virtio_dev_tx_packed(dev, vq, mbuf_pool, pkts, count, false);  }
> --
> 2.23.0