From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: passt.top; dmarc=none (p=none dis=none) header.from=gibson.dropbear.id.au Authentication-Results: passt.top; dkim=pass (2048-bit key; secure) header.d=gibson.dropbear.id.au header.i=@gibson.dropbear.id.au header.a=rsa-sha256 header.s=202602 header.b=nMvLdh2a; dkim-atps=neutral Received: from mail.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) by passt.top (Postfix) with ESMTPS id 1770A5A0265 for ; Mon, 11 May 2026 12:52:52 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gibson.dropbear.id.au; s=202602; t=1778496769; bh=FRARgs37WgFJaN7FlliGHjtbBOGtc3ZT27vX4BlSom8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nMvLdh2aJ3jg8t2/qrKETRZ3ysjrA4WgIlBmhraNMD772J1tyk6zBFMWyXaiy0h6z r+TrofkD1Q6fRKCFo9jl7VB6a0Ts2H1FAA3NcAV33SdTFXBvD9BHHcfB46p8XfqgWN H30xugwQCYuB58U5EC3e/ck3JG0DBK10BPo45PEiTrAw0S5z7jyNGIEgev66qgJFO8 +rVYN6afFqw3xC5386NXjgczvgUK6gOWF4lVsotbyA2WP/Smftfxo0ykjU5vU2Akxj AGY9IJZI0UglLV0ER3ijlyEi7GZjtX0pa0cYOPU0VBUbS9KLU5xSVB7TT2WcOSm+cD HP2J2Lk0pZcaA== Received: by gandalf.ozlabs.org (Postfix, from userid 1007) id 4gDc4x3yK6z4wJR; Mon, 11 May 2026 20:52:49 +1000 (AEST) Date: Mon, 11 May 2026 20:52:45 +1000 From: David Gibson To: Laurent Vivier Subject: Re: [PATCH v6 4/4] tcp_vu: Support multibuffer frames in tcp_vu_send_flag() Message-ID: References: <20260416161618.3826904-1-lvivier@redhat.com> <20260416161618.3826904-5-lvivier@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="kwYnQbzVWfVJzjD6" Content-Disposition: inline In-Reply-To: <20260416161618.3826904-5-lvivier@redhat.com> Message-ID-Hash: RRZALPOFTRZGMNFGMSFZ52RGNE7NXX6I X-Message-ID-Hash: RRZALPOFTRZGMNFGMSFZ52RGNE7NXX6I X-MailFrom: dgibson@gandalf.ozlabs.org X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: --kwYnQbzVWfVJzjD6 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Apr 16, 2026 at 06:16:18PM +0200, Laurent Vivier wrote: > Build the Ethernet, IP, and TCP headers on the stack instead of > directly in the buffer via pointer casts, then write them into the > iovec with IOV_PUSH_HEADER(). This mirrors the approach already used > in tcp_vu_prepare() and udp_vu_prepare(). >=20 > Remove the vu_eth(), vu_ip(), vu_payloadv4() and vu_payloadv6() helpers > from vu_common.h, as they are no longer used anywhere. >=20 > Introduce tcp_vu_send_dup() to handle DUP_ACK duplication using > vu_collect() and iov_memcopy() instead of a plain memcpy(), so that s/iov_memcopy/iov_memcpy/ > the duplicated frame is also properly scattered across multiple iovecs. >=20 > Signed-off-by: Laurent Vivier > --- > iov.c | 1 - > tcp_vu.c | 153 ++++++++++++++++++++++++++++++---------------------- > vu_common.h | 20 ------- > 3 files changed, 90 insertions(+), 84 deletions(-) >=20 > diff --git a/iov.c b/iov.c > index c0d9c6d21322..31fc3e479572 100644 > --- a/iov.c > +++ b/iov.c > @@ -208,7 +208,6 @@ void iov_memset(const struct iovec *iov, size_t iov_c= nt, size_t offset, int c, > * > * Return: total number of bytes copied > */ > -/* cppcheck-suppress unusedFunction */ > size_t iov_memcpy(struct iovec *dst_iov, size_t dst_iov_cnt, size_t dst_= offset, > const struct iovec *src_iov, size_t src_iov_cnt, > size_t src_offset, size_t length) > diff --git a/tcp_vu.c b/tcp_vu.c > index 96b16007701d..7f7e43860b10 100644 > --- a/tcp_vu.c > +++ b/tcp_vu.c > @@ -74,6 +74,42 @@ static size_t tcp_vu_hdrlen(bool v6) > return hdrlen; > } > =20 > +/** > + * tcp_vu_send_dup() - Duplicate a frame into a new virtqueue element > + * @c: Execution context > + * @vq: Receive virtqueue > + * @dest_elem: Destination virtqueue element to collect > + * @dest_iov: Destination iovec array for collected buffers > + * @max_dest_iov: Maximum number of entries in @dest_iov > + * @src_iov: Source iovec array containing the frame to duplicate > + * @src_cnt: Number of entries in @src_iov As Jon noted, @vnlen is missing. > + * > + * Return: number of virtqueue elements collected (0 if none available) > + */ > +static int tcp_vu_send_dup(const struct ctx *c, struct vu_virtq *vq, > + struct vu_virtq_element *dest_elem, > + struct iovec *dest_iov, size_t max_dest_iov, > + const struct iovec *src_iov, size_t src_cnt, > + size_t vnlen) > +{ > + const struct vu_dev *vdev =3D c->vdev; > + size_t dest_cnt; > + int elem_cnt; > + > + elem_cnt =3D vu_collect(vdev, vq, dest_elem, 1, dest_iov, max_dest_iov, > + &dest_cnt, vnlen, NULL); > + if (elem_cnt =3D=3D 0) > + return 0; > + > + iov_memcpy(dest_iov, dest_cnt, 0, src_iov, src_cnt, 0, > + MAX(VNET_HLEN + ETH_ZLEN, vnlen)); > + > + if (*c->pcap) > + pcap_iov(dest_iov, dest_cnt, VNET_HLEN, vnlen - VNET_HLEN); > + > + return elem_cnt; > +} > + > /** > * tcp_vu_send_flag() - Send segment with flags to vhost-user (no payloa= d) > * @c: Execution context > @@ -86,97 +122,88 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp= _tap_conn *conn, int flags) > { > struct vu_dev *vdev =3D c->vdev; > struct vu_virtq *vq =3D &vdev->vq[VHOST_USER_RX_QUEUE]; > + size_t optlen, hdrlen, iov_cnt, iov_used; > struct vu_virtq_element flags_elem[2]; Does the rationale for this having only 2 elements still apply? > - size_t optlen, hdrlen, l2len; > - struct ipv6hdr *ip6h =3D NULL; > - struct iphdr *ip4h =3D NULL; > - struct iovec flags_iov[2]; > - struct tcp_syn_opts *opts; > + struct iovec flags_iov[64]; > + int elem_cnt, dup_elem_cnt =3D 0; > + struct tcp_syn_opts opts; > struct iov_tail payload; > - struct tcphdr *th; > - struct ethhdr *eh; > + struct ipv6hdr ip6h; > + struct iphdr ip4h; > + struct tcphdr th; > + struct ethhdr eh; > uint32_t seq; > - int elem_cnt; > int ret; > =20 > hdrlen =3D tcp_vu_hdrlen(CONN_V6(conn)); > =20 > elem_cnt =3D vu_collect(vdev, vq, &flags_elem[0], 1, > - &flags_iov[0], 1, NULL, > - hdrlen + sizeof(*opts), NULL); > - if (elem_cnt !=3D 1) > + flags_iov, ARRAY_SIZE(flags_iov), &iov_cnt, > + hdrlen + sizeof(opts), NULL); > + if (elem_cnt =3D=3D 0) > return -1; > =20 > - assert(flags_elem[0].in_num =3D=3D 1); > - assert(flags_elem[0].in_sg[0].iov_len >=3D > - MAX(hdrlen + sizeof(*opts), ETH_ZLEN + VNET_HLEN)); > - > - eh =3D vu_eth(flags_elem[0].in_sg[0].iov_base); > - > - memcpy(eh->h_dest, c->guest_mac, sizeof(eh->h_dest)); > - memcpy(eh->h_source, c->our_tap_mac, sizeof(eh->h_source)); > - > - if (CONN_V4(conn)) { > - eh->h_proto =3D htons(ETH_P_IP); > - > - ip4h =3D vu_ip(flags_elem[0].in_sg[0].iov_base); > - *ip4h =3D (struct iphdr)L2_BUF_IP4_INIT(IPPROTO_TCP); > - > - th =3D vu_payloadv4(flags_elem[0].in_sg[0].iov_base); > - } else { > - eh->h_proto =3D htons(ETH_P_IPV6); > + memcpy(eh.h_dest, c->guest_mac, sizeof(eh.h_dest)); > =20 > - ip6h =3D vu_ip(flags_elem[0].in_sg[0].iov_base); > - *ip6h =3D (struct ipv6hdr)L2_BUF_IP6_INIT(IPPROTO_TCP); > - th =3D vu_payloadv6(flags_elem[0].in_sg[0].iov_base); > - } > + if (CONN_V4(conn)) > + ip4h =3D (struct iphdr)L2_BUF_IP4_INIT(IPPROTO_TCP); > + else > + ip6h =3D (struct ipv6hdr)L2_BUF_IP6_INIT(IPPROTO_TCP); > =20 > - memset(th, 0, sizeof(*th)); > - th->doff =3D sizeof(*th) / 4; > - th->ack =3D 1; Where are doff and ack now initialised? Or were these already unneeded? > + memset(&th, 0, sizeof(th)); This could be an initialiser now. > =20 > seq =3D conn->seq_to_tap; > - opts =3D (struct tcp_syn_opts *)(th + 1); > - ret =3D tcp_prepare_flags(c, conn, flags, th, opts, &optlen); > + ret =3D tcp_prepare_flags(c, conn, flags, &th, &opts, &optlen); > if (ret <=3D 0) { > - vu_queue_rewind(vq, 1); > + vu_queue_rewind(vq, elem_cnt); > return ret; > } > =20 > - payload =3D IOV_TAIL(flags_elem[0].in_sg, 1, hdrlen); > - > if (flags & KEEPALIVE) > seq--; > =20 > - tcp_fill_headers(c, conn, eh, ip4h, ip6h, th, &payload, > + iov_used =3D iov_skip_bytes(flags_iov, iov_cnt, > + MAX(optlen + hdrlen, VNET_HLEN + ETH_ZLEN), > + NULL); > + if (iov_used < iov_cnt) > + iov_used++; > + iov_cnt =3D iov_used; > + > + payload =3D IOV_TAIL(flags_elem[0].in_sg, iov_cnt, hdrlen); @payload here contains the TCP payload... > + iov_from_buf(payload.iov, payload.cnt, payload.off, &opts, optlen); > + tcp_fill_headers(c, conn, &eh, CONN_V4(conn) ? &ip4h : NULL, > + CONN_V6(conn) ? &ip6h : NULL, &th, &payload, > optlen, IP4_CSUM | (*c->pcap ? TCP_CSUM : 0), seq); > =20 > - vu_pad(flags_elem[0].in_sg, 1, hdrlen + optlen); > - vu_flush(vdev, vq, flags_elem, 1, hdrlen + optlen); > + vu_pad(flags_elem[0].in_sg, iov_cnt, hdrlen + optlen); > + > + /* write headers */ > + payload =3D IOV_TAIL(flags_elem[0].in_sg, iov_cnt, VNET_HLEN); =2E..but here contains the whole L2 frame, which seems confusing. Maybe name the variable differently? Or even a second variable? > + > + IOV_PUSH_HEADER(&payload, eh); > + if (CONN_V4(conn)) > + IOV_PUSH_HEADER(&payload, ip4h); > + else > + IOV_PUSH_HEADER(&payload, ip6h); > + IOV_PUSH_HEADER(&payload, th); > =20 > - l2len =3D hdrlen + optlen - VNET_HLEN; > if (*c->pcap) > - pcap_iov(&flags_elem[0].in_sg[0], 1, VNET_HLEN, l2len); > + pcap_iov(flags_elem[0].in_sg, iov_cnt, VNET_HLEN, > + hdrlen + optlen - VNET_HLEN); > =20 > if (flags & DUP_ACK) { > - elem_cnt =3D vu_collect(vdev, vq, &flags_elem[1], 1, > - &flags_iov[1], 1, NULL, > - hdrlen + optlen, NULL); > - if (elem_cnt =3D=3D 1 && > - flags_elem[1].in_sg[0].iov_len >=3D > - flags_elem[0].in_sg[0].iov_len) { > - memcpy(flags_elem[1].in_sg[0].iov_base, > - flags_elem[0].in_sg[0].iov_base, > - flags_elem[0].in_sg[0].iov_len); > - > - vu_flush(vdev, vq, &flags_elem[1], 1, hdrlen + optlen); > - > - if (*c->pcap) { > - pcap_iov(&flags_elem[1].in_sg[0], 1, VNET_HLEN, > - l2len); > - } > - } > + dup_elem_cnt =3D tcp_vu_send_dup(c, vq, &flags_elem[elem_cnt], > + &flags_iov[iov_cnt], > + ARRAY_SIZE(flags_iov) - iov_cnt, > + flags_elem[0].in_sg, iov_cnt, > + hdrlen + optlen); > } > + vu_flush(vdev, vq, flags_elem, elem_cnt, hdrlen + optlen); > + if (dup_elem_cnt) { > + vu_flush(vdev, vq, &flags_elem[elem_cnt], dup_elem_cnt, > + hdrlen + optlen); > + } > + > vu_queue_notify(vdev, vq); > =20 > return 0; > diff --git a/vu_common.h b/vu_common.h > index 51f70084a7cb..817384175a1d 100644 > --- a/vu_common.h > +++ b/vu_common.h > @@ -15,26 +15,6 @@ > #include "ip.h" > #include "virtio.h" > =20 > -static inline void *vu_eth(void *base) > -{ > - return ((char *)base + VNET_HLEN); > -} > - > -static inline void *vu_ip(void *base) > -{ > - return (struct ethhdr *)vu_eth(base) + 1; > -} > - > -static inline void *vu_payloadv4(void *base) > -{ > - return (struct iphdr *)vu_ip(base) + 1; > -} > - > -static inline void *vu_payloadv6(void *base) > -{ > - return (struct ipv6hdr *)vu_ip(base) + 1; > -} > - > int vu_collect(const struct vu_dev *vdev, struct vu_virtq *vq, > struct vu_virtq_element *elem, int max_elem, > struct iovec *in_sg, size_t max_in_sg, size_t *in_total, > --=20 > 2.53.0 >=20 --=20 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 --kwYnQbzVWfVJzjD6 Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEO+dNsU4E3yXUXRK2zQJF27ox2GcFAmoBtP0ACgkQzQJF27ox 2GcIYRAAhtMIu1oDd5qEaUTz21cDlFvotRd4ZkTp9u/BFEWqINRShN1q28qflQzN 9CflsmC7q6AEeXhhxB+loDEI8Xc9c2lemJUF+3r5N+vHhwwPs5cjc101cR7i11F6 7y2CilhjpM/OIj0ytJyANLUtDNZ1RBafRchTzEvYjQ1nna6wJJtTBCqJ+f2KzPaM /ktr2GNZT+E9vxDMSgwwruOkNdIlfoPlIMfRNdhmc/esVtosR8IkEs9UrPiEKKmn ucWfnU3JwTLcgg7GyOiUQMMCNab3IpJOMeObpbL4oeirY9IXsHtbPr7o7xTAV77J 8qBaNIoWQm5c9Jq2Sw1sbtCuD8ucH9b/i0QU1hbj+0IYhs95Gt1V1hpkflzcjXSv BqHjWG3d8blXv3J0YGmR+NOWCX/q8anjDT27rMKOGR3WI+Nym5vzTC5xRoawyfF2 72er3HazdjQs6xQETra/slaRGxiVTp+wTCN5m/BxJn7K6b6YKjK9xR6nRw/l21pQ GsJvWoZgVYOFagGwG0CWm2KIfLn66UpPx0mvLEnFSrKFsliQuvqX64b3zRWqbRbw c+iFv41E/cdqOjAvjWNaWY3Ovvv/lMzejnI8F36f7a0ehV43btpwLVt+Ruy4S0I6 /p05K7fiIAirsst8OJYeESgWbXdBxKsytDOpjC06XXMfqR93t6s= =oEtz -----END PGP SIGNATURE----- --kwYnQbzVWfVJzjD6--