From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E0540C61DA4 for ; Wed, 22 Feb 2023 11:24:33 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id 5251160F67; Wed, 22 Feb 2023 11:24:33 +0000 (UTC) DKIM-Filter: OpenDKIM Filter v2.11.0 smtp3.osuosl.org 5251160F67 Authentication-Results: smtp3.osuosl.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=IxOWeL99 X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id dufrJW46FDN7; Wed, 22 Feb 2023 11:24:32 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp3.osuosl.org (Postfix) with ESMTPS id 9A16660743; Wed, 22 Feb 2023 11:24:31 +0000 (UTC) DKIM-Filter: OpenDKIM Filter v2.11.0 smtp3.osuosl.org 9A16660743 Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 61255C0032; Wed, 22 Feb 2023 11:24:31 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [IPv6:2605:bc80:3010::138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 18FE9C002B for ; Wed, 22 Feb 2023 11:24:30 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id E1D2481992 for ; Wed, 22 Feb 2023 11:24:29 +0000 (UTC) DKIM-Filter: OpenDKIM Filter v2.11.0 smtp1.osuosl.org E1D2481992 Authentication-Results: smtp1.osuosl.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=IxOWeL99 X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id PLg8FfH08k7O for ; Wed, 22 Feb 2023 11:24:28 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 DKIM-Filter: OpenDKIM Filter v2.11.0 smtp1.osuosl.org 465D381769 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by smtp1.osuosl.org (Postfix) with ESMTPS id 465D381769 for ; Wed, 22 Feb 2023 11:24:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1677065067; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=RuR991O3W89jniq0oLJ77ACUn68KcHgToD/Kc8DJ8E8=; b=IxOWeL99P7Nwqfxcoe57IMDsBAnyaWRIbhCueRFUjIkFL0AtPdmcD5p8c9T4XZqHiY/FpO MNWo6Ko2skrb6DcK8u1dmBE3nAI4rcEFZ8zZRynTCrahSgarn1gLGHYNQs2m9cvKudjuJN W3XuISKc/ppDE1PdvqGIuqj2bsImZO4= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-592-ONebCfBjOZikJL5kjn-27A-1; Wed, 22 Feb 2023 06:24:25 -0500 X-MC-Unique: ONebCfBjOZikJL5kjn-27A-1 Received: by mail-wm1-f71.google.com with SMTP id l23-20020a7bc457000000b003e206cbce8dso3370336wmi.7 for ; Wed, 22 Feb 2023 03:24:25 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=RuR991O3W89jniq0oLJ77ACUn68KcHgToD/Kc8DJ8E8=; b=K8bUamQBvFzhusOXRBZcSdFc4SEoX29IQ1rLjhR6pjjx6MbK9KvAiv7qkhVIdPwmiO q/cN4bYNWLGbrj2Rf2P6tsTaZtIgDUdYAQs6P3K4DX4nhmb2R2X0a9qKFVPdls3iV4cz iQqddD2mF8npkP5EhK+uH0b1M3FxcrDBYop9sKl3hYLV/XYfq1ZjwkOL/eiIKY6g5WG1 YfO0sytXuaPU/aNEYrvfMLXUytS+ZTSeuC+LTYDWlITJDt+KrdGpcDkfihBnk64oxcvX V/LSetxkRbTzaQfrRd9CGFsdjqKTFeX66DNR4d69cV9pSZ35ZAUuD/RQu7ssbzRXPLLc As1Q== X-Gm-Message-State: AO0yUKVbGa5wtZ0vCGuh7ycGIRYZcc1dKj8eUofD8fWvofLxh2a3caa3 3bJxz+jyngiy23k6+4JOGGx15UWx2iX0cSZuXCsabyn7eOGY9trzb5TecZbc5KjpxOok8Di/j1e 4zzBR+m9nh9EymcDou5sPTSm2KMy+VRmPvpmHyRuyAA== X-Received: by 2002:a5d:554c:0:b0:2c5:9c7a:86a with SMTP id g12-20020a5d554c000000b002c59c7a086amr5776174wrw.22.1677065064442; Wed, 22 Feb 2023 03:24:24 -0800 (PST) X-Google-Smtp-Source: AK7set9ej0HSttfykbZ7EUBVAJC2Ml1o3MpEJH7HI5jIlYzxKjA5zFnJ0+TPjcZnlb2Qi2pgPhlW6A== X-Received: by 2002:a5d:554c:0:b0:2c5:9c7a:86a with SMTP id g12-20020a5d554c000000b002c59c7a086amr5776148wrw.22.1677065064080; Wed, 22 Feb 2023 03:24:24 -0800 (PST) Received: from redhat.com ([2.52.2.78]) by smtp.gmail.com with ESMTPSA id c15-20020adfef4f000000b002c54c9bd71fsm5007564wrp.93.2023.02.22.03.24.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Feb 2023 03:24:22 -0800 (PST) Date: Wed, 22 Feb 2023 06:24:18 -0500 From: "Michael S. Tsirkin" To: Jiri Pirko Subject: Re: [patch net-next v3] net: virtio_net: implement exact header length guest feature Message-ID: <20230222062208-mutt-send-email-mst@kernel.org> References: <20230222080638.382211-1-jiri@resnulli.us> MIME-Version: 1.0 In-Reply-To: <20230222080638.382211-1-jiri@resnulli.us> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: willemdebruijn.kernel@gmail.com, vmireyno@marvell.com, netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, davem@davemloft.net X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Wed, Feb 22, 2023 at 09:06:38AM +0100, Jiri Pirko wrote: > From: Jiri Pirko > > Virtio spec introduced a feature VIRTIO_NET_F_GUEST_HDRLEN which when > which when which when which when is probably unintentional :) >set implicates that device benefits from knowing the exact > size of the header. For compatibility, to signal to the device that > the header is reliable driver also needs to set this feature. > Without this feature set by driver, device has to figure > out the header size itself. > > Quoting the original virtio spec: > "hdr_len is a hint to the device as to how much of the header needs to > be kept to copy into each packet" > > "a hint" might not be clear for the reader what does it mean, if it is > "maybe like that" of "exactly like that". This feature just makes it > crystal clear and let the device count on the hdr_len being filled up > by the exact length of header. > > Also note the spec already has following note about hdr_len: > "Due to various bugs in implementations, this field is not useful > as a guarantee of the transport header size." > > Without this feature the device needs to parse the header in core > data path handling. Accurate information helps the device to eliminate > such header parsing and directly use the hardware accelerators > for GSO operation. > > virtio_net_hdr_from_skb() fills up hdr_len to skb_headlen(skb). > The driver already complies to fill the correct value. Introduce the > feature and advertise it. > > Note that virtio spec also includes following note for device > implementation: > "Caution should be taken by the implementation so as to prevent > a malicious driver from attacking the device by setting > an incorrect hdr_len." > > There is a plan to support this feature in our emulated device. > A device of SolidRun offers this feature bit. They claim this feature > will save the device a few cycles for every GSO packet. > > Link: https://docs.oasis-open.org/virtio/virtio/v1.2/cs01/virtio-v1.2-cs01.html#x1-230006x3 > Signed-off-by: Jiri Pirko > Reviewed-by: Parav Pandit > Reviewed-by: Alvaro Karsz > Acked-by: Michael S. Tsirkin > --- > v2->v3: > - changed the first paragraph in patch description according to > Michael's suggestion > - added Link tag with link to the spec > v1->v2: > - extended patch description > --- > drivers/net/virtio_net.c | 6 ++++-- > include/uapi/linux/virtio_net.h | 1 + > 2 files changed, 5 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index fb5e68ed3ec2..e85b03988733 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -62,7 +62,8 @@ static const unsigned long guest_offloads[] = { > VIRTIO_NET_F_GUEST_UFO, > VIRTIO_NET_F_GUEST_CSUM, > VIRTIO_NET_F_GUEST_USO4, > - VIRTIO_NET_F_GUEST_USO6 > + VIRTIO_NET_F_GUEST_USO6, > + VIRTIO_NET_F_GUEST_HDRLEN > }; > > #define GUEST_OFFLOAD_GRO_HW_MASK ((1ULL << VIRTIO_NET_F_GUEST_TSO4) | \ > @@ -4213,7 +4214,8 @@ static struct virtio_device_id id_table[] = { > VIRTIO_NET_F_CTRL_MAC_ADDR, \ > VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, \ > VIRTIO_NET_F_SPEED_DUPLEX, VIRTIO_NET_F_STANDBY, \ > - VIRTIO_NET_F_RSS, VIRTIO_NET_F_HASH_REPORT, VIRTIO_NET_F_NOTF_COAL > + VIRTIO_NET_F_RSS, VIRTIO_NET_F_HASH_REPORT, VIRTIO_NET_F_NOTF_COAL, \ > + VIRTIO_NET_F_GUEST_HDRLEN > > static unsigned int features[] = { > VIRTNET_FEATURES, > diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h > index b4062bed186a..12c1c9699935 100644 > --- a/include/uapi/linux/virtio_net.h > +++ b/include/uapi/linux/virtio_net.h > @@ -61,6 +61,7 @@ > #define VIRTIO_NET_F_GUEST_USO6 55 /* Guest can handle USOv6 in. */ > #define VIRTIO_NET_F_HOST_USO 56 /* Host can handle USO in. */ > #define VIRTIO_NET_F_HASH_REPORT 57 /* Supports hash report */ > +#define VIRTIO_NET_F_GUEST_HDRLEN 59 /* Guest provides the exact hdr_len value. */ > #define VIRTIO_NET_F_RSS 60 /* Supports RSS RX steering */ > #define VIRTIO_NET_F_RSC_EXT 61 /* extended coalescing info */ > #define VIRTIO_NET_F_STANDBY 62 /* Act as standby for another device > -- > 2.39.0 _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization