From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Monjalon Subject: Re: [PATCH v4 8/8] virtio/lib:add guest offload handle Date: Wed, 11 Nov 2015 11:19:32 +0100 Message-ID: <3146122.45QdW36GMG@xps13> References: <1447224046-1169-1-git-send-email-jijiang.liu@intel.com> <1447224046-1169-9-git-send-email-jijiang.liu@intel.com> <20151111082318.GY2326@yliu-dev.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: dev@dpdk.org To: Yuanhan Liu Return-path: Received: from mail-wm0-f48.google.com (mail-wm0-f48.google.com [74.125.82.48]) by dpdk.org (Postfix) with ESMTP id 016D38DA6 for ; Wed, 11 Nov 2015 11:20:44 +0100 (CET) Received: by wmww144 with SMTP id w144so38023705wmw.0 for ; Wed, 11 Nov 2015 02:20:43 -0800 (PST) In-Reply-To: <20151111082318.GY2326@yliu-dev.sh.intel.com> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Yuanhan, You deserve a "review award"! Thanks a lot 2015-11-11 16:23, Yuanhan Liu: > Regarding to your patch title, there are two minor pits: > > - the prefix should be "vhost" but not "virtio/lib". > > - you should add an extra space after ":" > > On Wed, Nov 11, 2015 at 02:40:46PM +0800, Jijiang Liu wrote: > > Enqueue guest offload(CSUM and TSO) handle. > > (ALL) Your patch lacks some explanation. And I don't think it's about > guest offload handling, it's about setting the right offload fields for > RX side, such as VIRTIO_NET_HDR_F_NEEDS_CSUM. > > And you need spend few words to state why that is required. Something > like following might help others to review: > > For packet going through from one VM to another VM without passing > the NIC, and the VM claiming that it supports checksum offload, > no one will actually calculate the checksum, hence, the packet > will be dropped at TCP layer, due to checksum validation is failed. > > However, for VM2VM case, there is no need to do checksum, for we > think the data should be reliable enough, and setting VIRTIO_NET_HDR_F_NEEDS_CSUM > at RX side will let the TCP layer to bypass the checksum validation, > so that the RX side could receive the packet in the end. > > At RX side, the offload information is inherited from mbuf, which is > in turn inherited from TX side. If we can still get those info at RX > side, it means the packet is from another VM at same host. So, it's > safe to set the VIRTIO_NET_HDR_F_NEEDS_CSUM, to skip checksum validation. > > > > Signed-off-by: Jijiang Liu > > --- > > lib/librte_vhost/vhost_rxtx.c | 45 +++++++++++++++++++++++++++++++++++++++- > > 1 files changed, 43 insertions(+), 2 deletions(-) > > > > diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c > > index 9e70990..468fed8 100644 > > --- a/lib/librte_vhost/vhost_rxtx.c > > +++ b/lib/librte_vhost/vhost_rxtx.c > > @@ -54,6 +54,42 @@ is_valid_virt_queue_idx(uint32_t idx, int is_tx, uint32_t qp_nb) > > return (is_tx ^ (idx & 1)) == 0 && idx < qp_nb * VIRTIO_QNUM; > > } > > > > +static void > > +virtio_enqueue_offload(struct rte_mbuf *m_buf, struct virtio_net_hdr *net_hdr) > > +{ > > As virtio_hdr is set per mbuf, you'd better reset net_hdr first before > setting it. Otherwise, if this mbuf has no offload related stuff, you > may still get a net_hdr with offload related fields set, due to last > mbuf has that. > > I know the chance is rare, but it's for code logic. > > > --yliu