From: David Gibson <david@gibson.dropbear.id.au>
To: Laurent Vivier <lvivier@redhat.com>
Cc: passt-dev@passt.top
Subject: Re: [PATCH 11/12] vu_common: Prepare to use multibuffer with guest RX
Date: Mon, 2 Mar 2026 11:59:08 +1100 [thread overview]
Message-ID: <aaTg3H2jHOBkBiU-@zatzit> (raw)
In-Reply-To: <20260227140330.2216753-12-lvivier@redhat.com>
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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
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next prev parent reply other threads:[~2026-03-02 1:03 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-27 14:03 [PATCH 00/12] vhost-user,udp: Handle multiple iovec entries per virtqueue element Laurent Vivier
2026-02-27 14:03 ` [PATCH 01/12] iov: Add iov_tail_truncate() and iov_tail_zero_end() Laurent Vivier
2026-03-01 23:47 ` David Gibson
2026-02-27 14:03 ` [PATCH 02/12] vhost-user: Use ARRAY_SIZE(elem) instead of VIRTQUEUE_MAX_SIZE Laurent Vivier
2026-03-01 23:48 ` David Gibson
2026-02-27 14:03 ` [PATCH 03/12] udp_vu: Use iov_tail to manage virtqueue buffers Laurent Vivier
2026-03-02 0:03 ` David Gibson
2026-02-27 14:03 ` [PATCH 04/12] udp_vu: Move virtqueue management from udp_vu_sock_recv() to its caller Laurent Vivier
2026-03-02 0:05 ` David Gibson
2026-02-27 14:03 ` [PATCH 05/12] iov: Add IOV_PUT_HEADER() to write header data back to iov_tail Laurent Vivier
2026-03-02 0:08 ` David Gibson
2026-02-27 14:03 ` [PATCH 06/12] udp: Pass iov_tail to udp_update_hdr4()/udp_update_hdr6() Laurent Vivier
2026-03-02 0:13 ` David Gibson
2026-02-27 14:03 ` [PATCH 07/12] udp_vu: Use iov_tail in udp_vu_prepare() Laurent Vivier
2026-03-02 0:24 ` David Gibson
2026-02-27 14:03 ` [PATCH 08/12] vu_common: Pass iov_tail to vu_set_vnethdr() Laurent Vivier
2026-03-02 0:51 ` David Gibson
2026-02-27 14:03 ` [PATCH 09/12] vu_common: Accept explicit iovec counts in vu_set_element() Laurent Vivier
2026-03-02 0:54 ` David Gibson
2026-02-27 14:03 ` [PATCH 10/12] vu_common: Accept explicit iovec count per element in vu_init_elem() Laurent Vivier
2026-03-02 0:55 ` David Gibson
2026-02-27 14:03 ` [PATCH 11/12] vu_common: Prepare to use multibuffer with guest RX Laurent Vivier
2026-03-02 0:59 ` David Gibson [this message]
2026-02-27 14:03 ` [PATCH 12/12] vhost-user,udp: Use 2 iovec entries per element Laurent Vivier
2026-03-02 1:03 ` David Gibson
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