[v3] vhost: enhance virtqueue access lock asserts

A simple comment in vhost_user_msg_handler() is not that robust.

Add a lock_all_qps property to message handlers so that their
implementation can add a build check and assert a vq is locked.

Signed-off-by: David Marchand <david.marchand@redhat.com>
---
Changes since v2:
- dropped review tags,
- following use of static_assert() in RTE_BUILD_BUG_ON, reworked build
  check by using enums (one enum is now defined per message type),
- as the added enums must be defined early, moved the definitions of
  handlers at the top of the file,

Changes since v1:
- moved this patch as the last of the series,

---
 lib/vhost/vhost_user.c | 128 +++++++++++++++++++++--------------------
 1 file changed, 66 insertions(+), 62 deletions(-)
  

On 2/26/24 18:05, David Marchand wrote:
> A simple comment in vhost_user_msg_handler() is not that robust.
> 
> Add a lock_all_qps property to message handlers so that their
> implementation can add a build check and assert a vq is locked.
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> ---
> Changes since v2:
> - dropped review tags,
> - following use of static_assert() in RTE_BUILD_BUG_ON, reworked build
>    check by using enums (one enum is now defined per message type),

Thanks for working on an alternative, it looks good to me:

Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Maxime

> - as the added enums must be defined early, moved the definitions of
>    handlers at the top of the file,
> 
> Changes since v1:
> - moved this patch as the last of the series,
> 
> ---
>   lib/vhost/vhost_user.c | 128 +++++++++++++++++++++--------------------
>   1 file changed, 66 insertions(+), 62 deletions(-)
> 
> diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
> index 3e8a87e517..84dae612c7 100644
> --- a/lib/vhost/vhost_user.c
> +++ b/lib/vhost/vhost_user.c
> @@ -56,14 +56,72 @@
>   #define INFLIGHT_ALIGNMENT	64
>   #define INFLIGHT_VERSION	0x1
>   
> -typedef struct vhost_message_handler {
> +typedef const struct vhost_message_handler {
>   	const char *description;
>   	int (*callback)(struct virtio_net **pdev, struct vhu_msg_context *ctx,
>   		int main_fd);
>   	bool accepts_fd;
> +	bool lock_all_qps;
>   } vhost_message_handler_t;
>   static vhost_message_handler_t vhost_message_handlers[];
>   
> +#define VHOST_MESSAGE_HANDLERS \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_NONE, NULL, false, false) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_GET_FEATURES, vhost_user_get_features, false, false) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_FEATURES, vhost_user_set_features, false, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_OWNER, vhost_user_set_owner, false, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_RESET_OWNER, vhost_user_reset_owner, false, false) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_MEM_TABLE, vhost_user_set_mem_table, true, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_LOG_BASE, vhost_user_set_log_base, true, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_LOG_FD, vhost_user_set_log_fd, true, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_VRING_NUM, vhost_user_set_vring_num, false, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_VRING_ADDR, vhost_user_set_vring_addr, false, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_VRING_BASE, vhost_user_set_vring_base, false, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_GET_VRING_BASE, vhost_user_get_vring_base, false, false) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_VRING_KICK, vhost_user_set_vring_kick, true, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_VRING_CALL, vhost_user_set_vring_call, true, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_VRING_ERR, vhost_user_set_vring_err, true, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_GET_PROTOCOL_FEATURES, vhost_user_get_protocol_features, \
> +	false, false) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_PROTOCOL_FEATURES, vhost_user_set_protocol_features, \
> +	false, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_GET_QUEUE_NUM, vhost_user_get_queue_num, false, false) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_VRING_ENABLE, vhost_user_set_vring_enable, false, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SEND_RARP, vhost_user_send_rarp, false, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_NET_SET_MTU, vhost_user_net_set_mtu, false, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_BACKEND_REQ_FD, vhost_user_set_req_fd, true, true) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_IOTLB_MSG, vhost_user_iotlb_msg, false, false) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_GET_CONFIG, vhost_user_get_config, false, false) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_CONFIG, vhost_user_set_config, false, false) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_POSTCOPY_ADVISE, vhost_user_set_postcopy_advise, false, false) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_POSTCOPY_LISTEN, vhost_user_set_postcopy_listen, false, false) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_POSTCOPY_END, vhost_user_postcopy_end, false, false) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_GET_INFLIGHT_FD, vhost_user_get_inflight_fd, false, false) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_INFLIGHT_FD, vhost_user_set_inflight_fd, true, false) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_SET_STATUS, vhost_user_set_status, false, false) \
> +VHOST_MESSAGE_HANDLER(VHOST_USER_GET_STATUS, vhost_user_get_status, false, false)
> +
> +#define VHOST_MESSAGE_HANDLER(id, handler, accepts_fd, lock_all_qps) \
> +	id ## _LOCK_ALL_QPS = lock_all_qps,
> +enum {
> +	VHOST_MESSAGE_HANDLERS
> +};
> +#undef VHOST_MESSAGE_HANDLER
> +
> +/* vhost_user_msg_handler() locks all qps based on a handler's lock_all_qps.
> + * Later, a handler may need to ensure the vq has been locked (for example,
> + * when calling lock annotated helpers).
> + *
> + * Note: unfortunately, static_assert() does not see an array content as a
> + * constant expression. Because of this, we can't simply check for
> + * vhost_user_msg_handler[].lock_all_qps.
> + * Instead, define an enum for each handler.
> + */
> +#define VHOST_USER_ASSERT_LOCK(dev, vq, id) do { \
> +	RTE_BUILD_BUG_ON(id ## _LOCK_ALL_QPS == false); \
> +	vq_assert_lock(dev, vq); \
> +} while (0)
> +
>   static int send_vhost_reply(struct virtio_net *dev, int sockfd, struct vhu_msg_context *ctx);
>   static int read_vhost_message(struct virtio_net *dev, int sockfd, struct vhu_msg_context *ctx);
>   
> @@ -400,7 +458,7 @@ vhost_user_set_features(struct virtio_net **pdev,
>   			cleanup_vq(vq, 1);
>   			cleanup_vq_inflight(dev, vq);
>   			/* vhost_user_lock_all_queue_pairs locked all qps */
> -			vq_assert_lock(dev, vq);
> +			VHOST_USER_ASSERT_LOCK(dev, vq, VHOST_USER_SET_FEATURES);
>   			rte_rwlock_write_unlock(&vq->access_lock);
>   			free_vq(dev, vq);
>   		}
> @@ -927,7 +985,7 @@ vhost_user_set_vring_addr(struct virtio_net **pdev,
>   	vq = dev->virtqueue[ctx->msg.payload.addr.index];
>   
>   	/* vhost_user_lock_all_queue_pairs locked all qps */
> -	vq_assert_lock(dev, vq);
> +	VHOST_USER_ASSERT_LOCK(dev, vq, VHOST_USER_SET_VRING_ADDR);
>   
>   	access_ok = vq->access_ok;
>   
> @@ -1442,7 +1500,7 @@ vhost_user_set_mem_table(struct virtio_net **pdev,
>   
>   		if (vq->desc || vq->avail || vq->used) {
>   			/* vhost_user_lock_all_queue_pairs locked all qps */
> -			vq_assert_lock(dev, vq);
> +			VHOST_USER_ASSERT_LOCK(dev, vq, VHOST_USER_SET_MEM_TABLE);
>   
>   			/*
>   			 * If the memory table got updated, the ring addresses
> @@ -2234,7 +2292,7 @@ vhost_user_set_vring_enable(struct virtio_net **pdev,
>   	vq = dev->virtqueue[index];
>   	if (!(dev->flags & VIRTIO_DEV_VDPA_CONFIGURED)) {
>   		/* vhost_user_lock_all_queue_pairs locked all qps */
> -		vq_assert_lock(dev, vq);
> +		VHOST_USER_ASSERT_LOCK(dev, vq, VHOST_USER_SET_VRING_ENABLE);
>   		if (enable && vq->async && vq->async->pkts_inflight_n) {
>   			VHOST_CONFIG_LOG(dev->ifname, ERR,
>   				"failed to enable vring. Inflight packets must be completed first");
> @@ -2838,42 +2896,8 @@ vhost_user_set_status(struct virtio_net **pdev,
>   	return RTE_VHOST_MSG_RESULT_OK;
>   }
>   
> -#define VHOST_MESSAGE_HANDLERS \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_NONE, NULL, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_GET_FEATURES, vhost_user_get_features, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_FEATURES, vhost_user_set_features, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_OWNER, vhost_user_set_owner, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_RESET_OWNER, vhost_user_reset_owner, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_MEM_TABLE, vhost_user_set_mem_table, true) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_LOG_BASE, vhost_user_set_log_base, true) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_LOG_FD, vhost_user_set_log_fd, true) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_VRING_NUM, vhost_user_set_vring_num, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_VRING_ADDR, vhost_user_set_vring_addr, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_VRING_BASE, vhost_user_set_vring_base, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_GET_VRING_BASE, vhost_user_get_vring_base, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_VRING_KICK, vhost_user_set_vring_kick, true) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_VRING_CALL, vhost_user_set_vring_call, true) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_VRING_ERR, vhost_user_set_vring_err, true) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_GET_PROTOCOL_FEATURES, vhost_user_get_protocol_features, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_PROTOCOL_FEATURES, vhost_user_set_protocol_features, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_GET_QUEUE_NUM, vhost_user_get_queue_num, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_VRING_ENABLE, vhost_user_set_vring_enable, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SEND_RARP, vhost_user_send_rarp, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_NET_SET_MTU, vhost_user_net_set_mtu, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_BACKEND_REQ_FD, vhost_user_set_req_fd, true) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_IOTLB_MSG, vhost_user_iotlb_msg, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_GET_CONFIG, vhost_user_get_config, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_CONFIG, vhost_user_set_config, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_POSTCOPY_ADVISE, vhost_user_set_postcopy_advise, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_POSTCOPY_LISTEN, vhost_user_set_postcopy_listen, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_POSTCOPY_END, vhost_user_postcopy_end, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_GET_INFLIGHT_FD, vhost_user_get_inflight_fd, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_INFLIGHT_FD, vhost_user_set_inflight_fd, true) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_SET_STATUS, vhost_user_set_status, false) \
> -VHOST_MESSAGE_HANDLER(VHOST_USER_GET_STATUS, vhost_user_get_status, false)
> -
> -#define VHOST_MESSAGE_HANDLER(id, handler, accepts_fd) \
> -	[id] = { #id, handler, accepts_fd },
> +#define VHOST_MESSAGE_HANDLER(id, handler, accepts_fd, lock_all_qps) \
> +	[id] = { #id, handler, accepts_fd, id ## _LOCK_ALL_QPS },
>   static vhost_message_handler_t vhost_message_handlers[] = {
>   	VHOST_MESSAGE_HANDLERS
>   };
> @@ -3141,31 +3165,11 @@ vhost_user_msg_handler(int vid, int fd)
>   	 * inactive, so it is safe. Otherwise taking the access_lock
>   	 * would cause a dead lock.
>   	 */
> -	switch (request) {
> -	case VHOST_USER_SET_FEATURES:
> -	case VHOST_USER_SET_PROTOCOL_FEATURES:
> -	case VHOST_USER_SET_OWNER:
> -	case VHOST_USER_SET_MEM_TABLE:
> -	case VHOST_USER_SET_LOG_BASE:
> -	case VHOST_USER_SET_LOG_FD:
> -	case VHOST_USER_SET_VRING_NUM:
> -	case VHOST_USER_SET_VRING_ADDR:
> -	case VHOST_USER_SET_VRING_BASE:
> -	case VHOST_USER_SET_VRING_KICK:
> -	case VHOST_USER_SET_VRING_CALL:
> -	case VHOST_USER_SET_VRING_ERR:
> -	case VHOST_USER_SET_VRING_ENABLE:
> -	case VHOST_USER_SEND_RARP:
> -	case VHOST_USER_NET_SET_MTU:
> -	case VHOST_USER_SET_BACKEND_REQ_FD:
> +	if (msg_handler->lock_all_qps) {
>   		if (!(dev->flags & VIRTIO_DEV_VDPA_CONFIGURED)) {
>   			vhost_user_lock_all_queue_pairs(dev);
>   			unlock_required = 1;
>   		}
> -		break;
> -	default:
> -		break;
> -
>   	}
>   
>   	handled = false;
  

On Mon, 26 Feb 2024 20:40:57 +0100
Maxime Coquelin <maxime.coquelin@redhat.com> wrote:

> > +
> > +/* vhost_user_msg_handler() locks all qps based on a handler's lock_all_qps.
> > + * Later, a handler may need to ensure the vq has been locked (for example,
> > + * when calling lock annotated helpers).
> > + *
> > + * Note: unfortunately, static_assert() does not see an array content as a
> > + * constant expression. Because of this, we can't simply check for
> > + * vhost_user_msg_handler[].lock_all_qps.
> > + * Instead, define an enum for each handler.
> > + */
> > +#define VHOST_USER_ASSERT_LOCK(dev, vq, id) do { \
> > +	RTE_BUILD_BUG_ON(id ## _LOCK_ALL_QPS == false); \

Rather than the opaque output of RTE_BUILD_BUG_ON, please use
static_assert() directly.