On Fri, Feb 27, 2026 at 03:03:29PM +0100, Laurent Vivier wrote:
> 1b95bd6fa114 ("vhost_user: fix multibuffer from linux") introduces
> multibuffer with TX (from the guest), but with iPXE we need to handle
> also multibuffer for RX (to the guest). This patch makes the parameter
> generic and global.
> 
> No functional change.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

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

In the sense that it does what it says on the tin.

Am I right in thinking this will only allow at most two buffers per
element for both to-guest and from-guest paths?  Having a fixed number
of buffers per element for the from-guest path seems a bit fragile.

> ---
>  vu_common.c | 6 ++----
>  vu_common.h | 2 ++
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/vu_common.c b/vu_common.c
> index e32a56d881a3..67d8f3e47338 100644
> --- a/vu_common.c
> +++ b/vu_common.c
> @@ -20,8 +20,6 @@
>  #include "migrate.h"
>  #include "epoll_ctl.h"
>  
> -#define VU_MAX_TX_BUFFER_NB	2
> -
>  /**
>   * vu_packet_check_range() - Check if a given memory zone is contained in
>   * 			     a mapped guest memory region
> @@ -184,11 +182,11 @@ static void vu_handle_tx(struct vu_dev *vdev, int index,
>  	count = 0;
>  	out_sg_count = 0;
>  	while (count < ARRAY_SIZE(elem) &&
> -	       out_sg_count + VU_MAX_TX_BUFFER_NB <= VIRTQUEUE_MAX_SIZE) {
> +	       out_sg_count + IOV_PER_ELEM <= VIRTQUEUE_MAX_SIZE) {
>  		int ret;
>  		struct iov_tail data;
>  
> -		elem[count].out_num = VU_MAX_TX_BUFFER_NB;
> +		elem[count].out_num = IOV_PER_ELEM;
>  		elem[count].out_sg = &out_sg[out_sg_count];
>  		elem[count].in_num = 0;
>  		elem[count].in_sg = NULL;
> diff --git a/vu_common.h b/vu_common.h
> index 51639c04df14..2c2d11abb26f 100644
> --- a/vu_common.h
> +++ b/vu_common.h
> @@ -9,6 +9,8 @@
>  #define VU_COMMON_H
>  #include <linux/virtio_net.h>
>  
> +#define IOV_PER_ELEM	(2)
> +
>  static inline void *vu_eth(void *base)
>  {
>  	return ((char *)base + VNET_HLEN);
> -- 
> 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