On Sun, Mar 03, 2024 at 05:13:26PM +0100, jan@openbsd.org wrote:
> On Thu, Feb 29, 2024 at 07:52:23AM -0600, Brian Conway wrote:
> > Original thread, sorry for breaking threading: https://marc.info/?l=openbsd-tech&m=170523759201797
> > 
> > Greetings. Are you still looking for testing on this? I went to give
> > it a spin today, but it no longer applies cleanly due to other recent
> > vio(4) work.
> 
> I will update and resend the diff after the release of 7.5.  So, there
> it more time for testing.  Before the 7.6 release.

Here is an updated version of the vio(4) TSO diff.  It takes some
advantage of the ether_extract_headers() improvements.  vlan(4) in
combination with vio(4) will work, but does not use TSO for now.  Thus,
no performance increase with vlan traffic.

I tested it with IPv4 and IPv6 on a Linux KVM host.

Tests are welcome.

ok?

bye,
Jan

Index: dev/pv/if_vio.c
===================================================================
RCS file: /cvs/src/sys/dev/pv/if_vio.c,v
diff -u -p -r1.31 if_vio.c
--- dev/pv/if_vio.c	14 Feb 2024 22:41:48 -0000	1.31
+++ dev/pv/if_vio.c	5 Apr 2024 18:40:08 -0000
@@ -43,12 +43,15 @@
 
 #include <net/if.h>
 #include <net/if_media.h>
+#include <net/route.h>
 
 #include <netinet/in.h>
 #include <netinet/if_ether.h>
 #include <netinet/ip.h>
 #include <netinet/ip6.h>
 #include <netinet/tcp.h>
+#include <netinet/tcp_timer.h>
+#include <netinet/tcp_var.h>
 #include <netinet/udp.h>
 
 #if NBPFILTER > 0
@@ -537,6 +540,9 @@ vio_attach(struct device *parent, struct
 	    VIRTIO_NET_F_MRG_RXBUF | VIRTIO_NET_F_CSUM |
 	    VIRTIO_F_RING_EVENT_IDX | VIRTIO_NET_F_GUEST_CSUM;
 
+	vsc->sc_driver_features |= VIRTIO_NET_F_HOST_TSO4;
+	vsc->sc_driver_features |= VIRTIO_NET_F_HOST_TSO6;
+
 	virtio_negotiate_features(vsc, virtio_net_feature_names);
 	if (virtio_has_feature(vsc, VIRTIO_NET_F_MAC)) {
 		vio_get_lladdr(&sc->sc_ac, vsc);
@@ -553,9 +559,9 @@ vio_attach(struct device *parent, struct
 		sc->sc_hdr_size = offsetof(struct virtio_net_hdr, num_buffers);
 	}
 	if (virtio_has_feature(vsc, VIRTIO_NET_F_MRG_RXBUF))
-		ifp->if_hardmtu = 16000; /* arbitrary limit */
+		ifp->if_hardmtu = MAXMCLBYTES;
 	else
-		ifp->if_hardmtu = MCLBYTES - sc->sc_hdr_size - ETHER_HDR_LEN;
+		ifp->if_hardmtu = MAXMCLBYTES - sc->sc_hdr_size - ETHER_HDR_LEN;
 
 	if (virtio_alloc_vq(vsc, &sc->sc_vq[VQRX], 0, MCLBYTES, 2, "rx") != 0)
 		goto err;
@@ -595,6 +601,10 @@ vio_attach(struct device *parent, struct
 	if (virtio_has_feature(vsc, VIRTIO_NET_F_CSUM))
 		ifp->if_capabilities |= IFCAP_CSUM_TCPv4|IFCAP_CSUM_UDPv4|
 		    IFCAP_CSUM_TCPv6|IFCAP_CSUM_UDPv6;
+	if (virtio_has_feature(vsc, VIRTIO_NET_F_HOST_TSO4))
+		ifp->if_capabilities |= IFCAP_TSOv4;
+	if (virtio_has_feature(vsc, VIRTIO_NET_F_HOST_TSO6))
+		ifp->if_capabilities |= IFCAP_TSOv6;
 	ifq_init_maxlen(&ifp->if_snd, vsc->sc_vqs[1].vq_num - 1);
 	ifmedia_init(&sc->sc_media, 0, vio_media_change, vio_media_status);
 	ifmedia_add(&sc->sc_media, IFM_ETHER | IFM_AUTO, 0, NULL);
@@ -714,6 +724,74 @@ vio_stop(struct ifnet *ifp, int disable)
 	}
 }
 
+static inline uint16_t
+vio_tso_cksum(uint32_t cksum, uint16_t paylen)
+{
+	/* Add payload length */
+	cksum += paylen;
+
+	/* Fold back to 16 bit */
+	cksum += cksum >> 16;
+
+	return (uint16_t)(cksum);
+}
+
+void
+vio_tx_offload(struct virtio_net_hdr *hdr, struct mbuf *m)
+{
+	struct ether_extracted ext;
+
+	/*
+	 * Checksum Offload
+	 */
+
+	if (!ISSET(m->m_pkthdr.csum_flags, M_TCP_CSUM_OUT) &&
+	    !ISSET(m->m_pkthdr.csum_flags, M_UDP_CSUM_OUT))
+		return;
+
+	ether_extract_headers(m, &ext);
+	hdr->csum_start = sizeof(*ext.eh);
+#if NVLAN > 0
+	if (ext.evh)
+		hdr->csum_start = sizeof(*ext.evh);
+#endif
+	if (ext.ip4 || ext.ip6)
+		hdr->csum_start += ext.iphlen;
+
+	if (m->m_pkthdr.csum_flags & M_TCP_CSUM_OUT)
+		hdr->csum_offset = offsetof(struct tcphdr, th_sum);
+	else
+		hdr->csum_offset = offsetof(struct udphdr, uh_sum);
+
+	hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
+
+	/*
+	 * TCP Segmentation Offload
+	 */
+
+	if (!ISSET(m->m_pkthdr.csum_flags, M_TCP_TSO))
+		return;
+
+	hdr->hdr_len = hdr->csum_start + ext.tcphlen;
+	hdr->gso_size = m->m_pkthdr.ph_mss;
+
+	if (ext.ip4)
+		hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
+#ifdef INET6
+	else if (ext.ip6)
+		hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
+#endif
+	else
+		tcpstat_inc(tcps_outbadtso);
+
+	/* VirtIO-Net need pseudo header cksum with IP-payload length for TSO */
+	ext.tcp->th_sum = vio_tso_cksum(ext.tcp->th_sum,
+	    htons(ext.iplen - ext.iphlen));
+
+	tcpstat_add(tcps_outpkttso,
+	    (ext.paylen + m->m_pkthdr.ph_mss - 1) / m->m_pkthdr.ph_mss);
+}
+
 void
 vio_start(struct ifnet *ifp)
 {
@@ -750,24 +828,7 @@ again:
 
 		hdr = &sc->sc_tx_hdrs[slot];
 		memset(hdr, 0, sc->sc_hdr_size);
-		if (m->m_pkthdr.csum_flags & (M_TCP_CSUM_OUT|M_UDP_CSUM_OUT)) {
-			struct ether_extracted ext;
-
-			ether_extract_headers(m, &ext);
-			hdr->csum_start = sizeof(*ext.eh);
-#if NVLAN > 0
-			if (ext.evh)
-				hdr->csum_start = sizeof(*ext.evh);
-#endif
-			if (m->m_pkthdr.csum_flags & M_TCP_CSUM_OUT)
-				hdr->csum_offset = offsetof(struct tcphdr, th_sum);
-			else
-				hdr->csum_offset = offsetof(struct udphdr, uh_sum);
-
-			if (ext.ip4 || ext.ip6)
-				hdr->csum_start += ext.iphlen;
-			hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
-		}
+		vio_tx_offload(hdr, m);
 
 		r = vio_encap(sc, slot, m);
 		if (r != 0) {