Re: [PATCH 09/12] vu_common: Accept explicit iovec counts in vu_set_element()

[David Gibson <david@gibson.dropbear.id.au>]

[-- Attachment #1: Type: text/plain, Size: 3696 bytes --]

On Fri, Feb 27, 2026 at 03:03:27PM +0100, Laurent Vivier wrote:
> Previously, vu_set_element() derived the number of iovec entries from
> whether the pointer was NULL or not (using !!out_sg and !!in_sg). This
> implicitly limited each virtqueue element to at most one iovec per
> direction.
> 
> Change the function signature to accept explicit out_num and in_num
> parameters, allowing callers to specify multiple iovec entries per
> element when needed. Update all existing call sites to pass the
> equivalent values (0 for NULL pointers, 1 for valid pointers).
> 
> No functional change.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  tcp_vu.c    |  4 ++--
>  vu_common.c |  5 +++--
>  vu_common.h | 13 ++++++++-----
>  3 files changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/tcp_vu.c b/tcp_vu.c
> index 92667507ac9b..77d6e75496a0 100644
> --- a/tcp_vu.c
> +++ b/tcp_vu.c
> @@ -87,7 +87,7 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
>  
>  	hdrlen = tcp_vu_hdrlen(CONN_V6(conn));
>  
> -	vu_set_element(&flags_elem[0], NULL, &flags_iov[0]);
> +	vu_set_element(&flags_elem[0], 0, NULL, 1, &flags_iov[0]);
>  
>  	elem_cnt = vu_collect(vdev, vq, &flags_elem[0], 1,
>  			      MAX(hdrlen + sizeof(*opts), ETH_ZLEN + VNET_HLEN), NULL);
> @@ -149,7 +149,7 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
>  	nb_ack = 1;
>  
>  	if (flags & DUP_ACK) {
> -		vu_set_element(&flags_elem[1], NULL, &flags_iov[1]);
> +		vu_set_element(&flags_elem[1], 0, NULL, 1, &flags_iov[1]);
>  
>  		elem_cnt = vu_collect(vdev, vq, &flags_elem[1], 1,
>  				      flags_elem[0].in_sg[0].iov_len, NULL);
> diff --git a/vu_common.c b/vu_common.c
> index a8d5fcdaea83..b6753a556049 100644
> --- a/vu_common.c
> +++ b/vu_common.c
> @@ -59,12 +59,13 @@ int vu_packet_check_range(struct vdev_memory *memory,
>   * @iov:	Array of iovec to assign to virtqueue element
>   * @elem_cnt:	Number of virtqueue element
>   */
> -void vu_init_elem(struct vu_virtq_element *elem, struct iovec *iov, int elem_cnt)
> +void vu_init_elem(struct vu_virtq_element *elem, struct iovec *iov,
> +		  int elem_cnt)
>  {
>  	int i;
>  
>  	for (i = 0; i < elem_cnt; i++)
> -		vu_set_element(&elem[i], NULL, &iov[i]);
> +		vu_set_element(&elem[i], 0, NULL, 1, &iov[i]);
>  }
>  
>  /**
> diff --git a/vu_common.h b/vu_common.h
> index 41cf18936300..c1d2ce888f12 100644
> --- a/vu_common.h
> +++ b/vu_common.h
> @@ -32,15 +32,18 @@ static inline void *vu_payloadv6(void *base)
>  /**
>   * vu_set_element() - Initialize a vu_virtq_element
>   * @elem:	Element to initialize
> - * @out_sg:	One out iovec entry to set in elem
> - * @in_sg:	One in iovec entry to set in elem
> + * @out_num:	Number of outgoing iovec buffers
> + * @out_sg:	Out iovec entry to set in elem
> + * @in_num:	Number of incoming iovec buffers
> + * @in_sg:	In iovec entry to set in elem
>   */
>  static inline void vu_set_element(struct vu_virtq_element *elem,
> -				  struct iovec *out_sg, struct iovec *in_sg)
> +				  unsigned int out_num, struct iovec *out_sg,
> +				  unsigned int in_num, struct iovec *in_sg)
>  {
> -	elem->out_num = !!out_sg;
> +	elem->out_num = out_num;
>  	elem->out_sg = out_sg;
> -	elem->in_num = !!in_sg;
> +	elem->in_num = in_num;
>  	elem->in_sg = in_sg;
>  }
>  
> -- 
> 2.53.0
> 

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]