From patchwork Mon Dec 18 11:37:11 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steffen Trumtrar X-Patchwork-Id: 13496738 X-Patchwork-Delegate: kuba@kernel.org Received: from metis.whiteo.stw.pengutronix.de (metis.whiteo.stw.pengutronix.de [185.203.201.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 83E6B3715D for ; Mon, 18 Dec 2023 11:38:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=pengutronix.de Received: from ptz.office.stw.pengutronix.de ([2a0a:edc0:0:900:1d::77] helo=ratatoskr.trumtrar.info) by metis.whiteo.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1rFBwa-0000Vp-1R; Mon, 18 Dec 2023 12:37:56 +0100 From: Steffen Trumtrar Date: Mon, 18 Dec 2023 12:37:11 +0100 Subject: [PATCH RFC 4/4] virtio-net: support future packet transmit time Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20231218-v6-7-topic-virtio-net-ptp-v1-4-cac92b2d8532@pengutronix.de> References: <20231218-v6-7-topic-virtio-net-ptp-v1-0-cac92b2d8532@pengutronix.de> In-Reply-To: <20231218-v6-7-topic-virtio-net-ptp-v1-0-cac92b2d8532@pengutronix.de> To: "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Richard Cochran Cc: virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Willem de Bruijn X-Mailer: b4 0.12.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=3486; i=s.trumtrar@pengutronix.de; h=from:subject:message-id; bh=EJKihRWjT7yjMqK7mYnH5LqaBkCEuOfwqbOCbJtPME4=; b=owGbwMvMwCUmvd38QH3grB+Mp9WSGFIb9DlzuBpkjv/4xRqe7PNzyqbvkl0fPvhOcl38L1LD4Vv9 BFaHjlIWBjEuBlkxRZbItYc0Ngt/1vly/DwDzBxWJpAhDFycAjARXimG/yHrJpyqnCP0fNO1iYbWpt 8fqRbxd+oskHC31OVeFmddu5+R4ULJFDenlOA/+S+WXTzoYubj0PPN5V3nu90c11cp3Zv8nxkA X-Developer-Key: i=s.trumtrar@pengutronix.de; a=openpgp; fpr=59ADC228B313F32CF4C7CF001BB737C07F519AF8 X-SA-Exim-Connect-IP: 2a0a:edc0:0:900:1d::77 X-SA-Exim-Mail-From: s.trumtrar@pengutronix.de X-SA-Exim-Scanned: No (on metis.whiteo.stw.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org X-Patchwork-State: RFC From: Willem de Bruijn Add optional transmit time (SO_TXTIME) offload for virtio-net. The Linux TCP/IP stack tries to avoid bursty transmission and network congestion through pacing: computing an skb delivery time based on congestion information. Userspace protocol implementations can achieve the same with SO_TXTIME. This may also reduce scheduling jitter and improve RTT estimation. Pacing can be implemented in ETF or FQ qdiscs or offloaded to NIC hardware. Allow virtio-net driver to offload for the same reasons. The timestamp straddles (virtual) hardware domains. Like PTP, use international atomic time (CLOCK_TAI) as global clock base. The driver must sync with the device, e.g., through kvm-clock. Changes RFC - RFCv2 - rename from transmit timestamp to future packet transmit time - convert cpu_to_virtioXX to cpu_to_leXX Signed-off-by: Willem de Bruijn Signed-off-by: Steffen Trumtrar --- drivers/net/virtio_net.c | 13 ++++++++++++- include/uapi/linux/virtio_net.h | 1 + 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 4065834957fbd..fb3572074e8b8 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -286,6 +286,9 @@ struct virtnet_info { /* Device will pass tx timestamp. Requires has_tx_tstamp */ bool enable_tx_tstamp; + /* Driver will pass CLOCK_TAI delivery time to the device */ + bool has_tx_time; + /* Has control virtqueue */ bool has_cvq; @@ -2371,6 +2374,8 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb) } if (vi->enable_tx_tstamp && skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) ht->hash.hdr.flags |= VIRTIO_NET_HDR_F_TSTAMP; + if (vi->has_tx_time && skb->tstamp) + ht->tstamp = cpu_to_le64(skb->tstamp); sg_init_table(sq->sg, skb_shinfo(skb)->nr_frags + (can_push ? 1 : 2)); if (can_push) { @@ -4698,6 +4703,11 @@ static int virtnet_probe(struct virtio_device *vdev) vi->hdr_len = sizeof(struct virtio_net_hdr_hash_ts); } + if (virtio_has_feature(vdev, VIRTIO_NET_F_TX_TIME)) { + vi->has_tx_time = true; + vi->hdr_len = sizeof(struct virtio_net_hdr_hash_ts); + } + if (virtio_has_feature(vdev, VIRTIO_F_ANY_LAYOUT) || virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) vi->any_header_sg = true; @@ -4941,7 +4951,8 @@ static struct virtio_device_id id_table[] = { VIRTIO_NET_F_RSS, VIRTIO_NET_F_HASH_REPORT, VIRTIO_NET_F_NOTF_COAL, \ VIRTIO_NET_F_VQ_NOTF_COAL, \ VIRTIO_NET_F_GUEST_HDRLEN, \ - VIRTIO_NET_F_TX_HASH, VIRTIO_NET_F_RX_TSTAMP, VIRTIO_NET_F_TX_TSTAMP + VIRTIO_NET_F_TX_HASH, VIRTIO_NET_F_RX_TSTAMP, VIRTIO_NET_F_TX_TSTAMP, \ + VIRTIO_NET_F_TX_TIME static unsigned int features[] = { VIRTNET_FEATURES, diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h index 03a7ef45372d7..18db1e1130d92 100644 --- a/include/uapi/linux/virtio_net.h +++ b/include/uapi/linux/virtio_net.h @@ -56,6 +56,7 @@ #define VIRTIO_NET_F_MQ 22 /* Device supports Receive Flow * Steering */ #define VIRTIO_NET_F_CTRL_MAC_ADDR 23 /* Set MAC address */ +#define VIRTIO_NET_F_TX_TIME 48 /* Driver sets TAI delivery time */ #define VIRTIO_NET_F_TX_TSTAMP 49 /* Device sends TAI transmit time */ #define VIRTIO_NET_F_RX_TSTAMP 50 /* Device sends TAI receive time */ #define VIRTIO_NET_F_TX_HASH 51 /* Driver sends hash report */