From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 1688D30DEA3 for ; Wed, 26 Nov 2025 06:29:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764138547; cv=none; b=bgq8Yr0yZSx8aXf6sOqKO2OTRADi3ymAz9a9foJumfM8ZPbqUG3vcLPVoc/8jhjClil/K7eV9N+m6sFYY7KazOtQqV04+2LOzpTisQQSuEmmup7JXU89rn7bN4dcb1YRubkfLefvHXApI6jcgCCwcgN9vJbOzf8TIEuuB1HpKZI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764138547; c=relaxed/simple; bh=3/pwaE5kNWc6xvRP4byT6Z1o7udkRNYHajixp1MyjGw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=INsIElU+iKND0Dvjj/bUoex9FsL28GN/xpQsbu5ZBUXEqE47XFojRpDXkozQsB2Iy4EdSwjB/DS+85VPlzA/OcACQ2I363HTPU0ilj4b6sDDqO6BZdKGCIfK29JObbo5v+1vzfcgZ/eoUK4H3iZBxW5sNxeYcJhAnhUerXTqho0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=QtTBx1GB; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=FLBzkVDO; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="QtTBx1GB"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="FLBzkVDO" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1764138545; 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=eRoHaibIPNdZFAseTrDimat8Kh1F+X2mpCLBomjQqzI=; b=QtTBx1GBu0Pr43+yuPSuRn+yXZ3ynGpv69q50x56nPJ1Cju9rPr50Ji3bZ6jiZ1EsL6bU1 k2t9xDmPqsKuqyOFqvNnTupbZYiXSz8Zfq4HD2NdkmeRMki4djIqOsU4ZhM6FMgDiBzc6A +NPptrXDEysaZwjJgp4nfFP3fptdcU0= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-516-0j_NsX_AM1-q1LncfpkObA-1; Wed, 26 Nov 2025 01:29:02 -0500 X-MC-Unique: 0j_NsX_AM1-q1LncfpkObA-1 X-Mimecast-MFC-AGG-ID: 0j_NsX_AM1-q1LncfpkObA_1764138542 Received: by mail-wr1-f69.google.com with SMTP id ffacd0b85a97d-429cdb0706aso4207978f8f.0 for ; Tue, 25 Nov 2025 22:29:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1764138541; x=1764743341; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=eRoHaibIPNdZFAseTrDimat8Kh1F+X2mpCLBomjQqzI=; b=FLBzkVDOEZ0WJ7ItfxerPQEd+dCfbjjQGAe8+eQKZOxRaxLStQZo4MeCbqMn71MFYX dMkEwqBcAw5au4zb6vm7qeNE0uoGlkpYaEsZZNSHACEEOphW9S8I83LzsDJcgTSTOm8i mFmCOAZ7WVzjBi7oe50kRJae+HS8brqrA10aosDi8zvX0PrhQnvZXgtCeocdwnfDdQ1c FYeW9DuAdvITslU6OPVd6rsBX8xoqwlRB0TACQX1E/NVgoTj5CEQuplTONZ1/J0b3u+t Qu2Q4dyxA9lWQ4IDKCx0B4x624qB3aiXfDBuL2CDf0U0f+5MPJpK9xEgwoDfzTpO5u9N anPg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1764138541; x=1764743341; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=eRoHaibIPNdZFAseTrDimat8Kh1F+X2mpCLBomjQqzI=; b=HWQ99NHHOKsepGMQgq/PGIFHqTDxNQvd+V5Xd3vx18yASP0KfIUhHXqS3/MI6EkQcr b2ieERmYiwEf8scVcT86m0cGDF3mUbPwrZ8SQdwGn0Wiv/SjGAuTV0sd63z4wLeQvHyn /AdwCLXVXaIIKCzbcWpYlao9hRXzYjlsFjPXUHyug6x0auW44d47m+vPuNGs9lox+6gv uGcZJRjW0fmo6sNpx/flv7cFy3bohdBzyhx0XDKa4gvOUcU0EjWccakykalPgFb0/AB5 9ZDxqgIs27VrecKqNiPwwRo1htBf940qqwulk0l9i39V5wPv7Ehlb8qLuy9w5CTaL9Tu RDtg== X-Forwarded-Encrypted: i=1; AJvYcCV2atPZhVDNYpE/na3Ranb3UGdSJkjKACb0yEB9C5RYwUJ4n54EkvGdgFhnKETjcn/695twKXTg7wg2HFA=@vger.kernel.org X-Gm-Message-State: AOJu0Yz+75vX17FN+yR2lTEg01x7UJus+pnvvFt1is02Mp2H8Xdp4idl Hqx9G4un62WJwwspwDix//7zup6ShdIlEyRP70tpgId39ttQPqIMiC1u5GR9cUNxA9pHLx8wVTX fRVa05eGMACdImhvP75TQQDLb/s8D3yntAEs5vs6gLIpCtbhQ7C867p8qSerug/qGqA== X-Gm-Gg: ASbGncvqQxjJA8oc4ugr6/qeJPJXWsgXEgej2i6toRhuS19q/h8oz/iC39p+mzoe6AN YIhgDQka08q+n73tTW2YcZeJC4HQ1cBRHcgSA5K4YqtYRqhfcZ4yrw06Jd5pf9uz0CQfXijgHeR aVtQ511D4m7q/CSvxlQEnsWHHXv8h9+hYK22q4T0SgatoggUmD+Z5iS24Xf9yEJbNP51837yCvl C+cCS8Y2hxaxzASFkCRSJb7dY3nzBCW/7yUCQpr07higWGPhDZ4qULiNmsqZIz0GivynmJhk98b LKnDO4heLlU8mxtsHwdMKXVw0iqvRK79k6CDQ1COYDOJ+HPZVpj5Rhwf1VPZgIJ81jESce9IfQZ Y3dYT2J/BdaTqlloOiw2oqwtmiheKig== X-Received: by 2002:a05:6000:1445:b0:42b:3ed2:c08a with SMTP id ffacd0b85a97d-42cc1cbd06dmr19876148f8f.13.1764138541591; Tue, 25 Nov 2025 22:29:01 -0800 (PST) X-Google-Smtp-Source: AGHT+IGz3A2mfZSj7obvLm5ShaXHAmTMrtQXHYWQePIsCFH4Le2VTsSdvCCTNjdEfLEsFspW6+5HWQ== X-Received: by 2002:a05:6000:1445:b0:42b:3ed2:c08a with SMTP id ffacd0b85a97d-42cc1cbd06dmr19876120f8f.13.1764138541147; Tue, 25 Nov 2025 22:29:01 -0800 (PST) Received: from redhat.com (IGLD-80-230-39-63.inter.net.il. [80.230.39.63]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-42cb7f2e574sm38233964f8f.3.2025.11.25.22.28.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Nov 2025 22:29:00 -0800 (PST) Date: Wed, 26 Nov 2025 01:28:57 -0500 From: "Michael S. Tsirkin" To: Jon Kohler Cc: Willem de Bruijn , Jason Wang , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux.dev Subject: Re: [PATCH net v3] virtio-net: avoid unnecessary checksum calculation on guest RX Message-ID: <20251126012848-mutt-send-email-mst@kernel.org> References: <20251125222754.1737443-1-jon@nutanix.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251125222754.1737443-1-jon@nutanix.com> On Tue, Nov 25, 2025 at 03:27:53PM -0700, Jon Kohler wrote: > Commit a2fb4bc4e2a6 ("net: implement virtio helpers to handle UDP > GSO tunneling.") inadvertently altered checksum offload behavior > for guests not using UDP GSO tunneling. > > Before, tun_put_user called tun_vnet_hdr_from_skb, which passed > has_data_valid = true to virtio_net_hdr_from_skb. > > After, tun_put_user began calling tun_vnet_hdr_tnl_from_skb instead, > which passes has_data_valid = false into both call sites. > > This caused virtio hdr flags to not include VIRTIO_NET_HDR_F_DATA_VALID > for SKBs where skb->ip_summed == CHECKSUM_UNNECESSARY. As a result, > guests are forced to recalculate checksums unnecessarily. > > Restore the previous behavior by ensuring has_data_valid = true is > passed in the !tnl_gso_type case, but only from tun side, as > virtio_net_hdr_tnl_from_skb() is used also by the virtio_net driver, > which in turn must not use VIRTIO_NET_HDR_F_DATA_VALID on tx. > > Cc: Paolo Abeni > Fixes: a2fb4bc4e2a6 ("net: implement virtio helpers to handle UDP GSO tunneling.") > Signed-off-by: Jon Kohler Acked-by: Michael S. Tsirkin > --- > v2-v3: Add net tag (whoops, sorry!) > v1-v2: Add arg to avoid conflict from driver (Paolo) and send to net > instead of net-next. > drivers/net/tun_vnet.h | 2 +- > drivers/net/virtio_net.c | 3 ++- > include/linux/virtio_net.h | 7 ++++--- > 3 files changed, 7 insertions(+), 5 deletions(-) > > diff --git a/drivers/net/tun_vnet.h b/drivers/net/tun_vnet.h > index 81662328b2c7..a5f93b6c4482 100644 > --- a/drivers/net/tun_vnet.h > +++ b/drivers/net/tun_vnet.h > @@ -244,7 +244,7 @@ tun_vnet_hdr_tnl_from_skb(unsigned int flags, > > if (virtio_net_hdr_tnl_from_skb(skb, tnl_hdr, has_tnl_offload, > tun_vnet_is_little_endian(flags), > - vlan_hlen)) { > + vlan_hlen, true)) { > struct virtio_net_hdr_v1 *hdr = &tnl_hdr->hash_hdr.hdr; > struct skb_shared_info *sinfo = skb_shinfo(skb); > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index cfa006b88688..96f2d2a59003 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -3339,7 +3339,8 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb, bool orphan) > hdr = &skb_vnet_common_hdr(skb)->tnl_hdr; > > if (virtio_net_hdr_tnl_from_skb(skb, hdr, vi->tx_tnl, > - virtio_is_little_endian(vi->vdev), 0)) > + virtio_is_little_endian(vi->vdev), 0, > + false)) > return -EPROTO; > > if (vi->mergeable_rx_bufs) > diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h > index b673c31569f3..75dabb763c65 100644 > --- a/include/linux/virtio_net.h > +++ b/include/linux/virtio_net.h > @@ -384,7 +384,8 @@ virtio_net_hdr_tnl_from_skb(const struct sk_buff *skb, > struct virtio_net_hdr_v1_hash_tunnel *vhdr, > bool tnl_hdr_negotiated, > bool little_endian, > - int vlan_hlen) > + int vlan_hlen, > + bool has_data_valid) > { > struct virtio_net_hdr *hdr = (struct virtio_net_hdr *)vhdr; > unsigned int inner_nh, outer_th; > @@ -394,8 +395,8 @@ virtio_net_hdr_tnl_from_skb(const struct sk_buff *skb, > tnl_gso_type = skb_shinfo(skb)->gso_type & (SKB_GSO_UDP_TUNNEL | > SKB_GSO_UDP_TUNNEL_CSUM); > if (!tnl_gso_type) > - return virtio_net_hdr_from_skb(skb, hdr, little_endian, false, > - vlan_hlen); > + return virtio_net_hdr_from_skb(skb, hdr, little_endian, > + has_data_valid, vlan_hlen); > > /* Tunnel support not negotiated but skb ask for it. */ > if (!tnl_hdr_negotiated) > -- > 2.43.0