From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751858AbdGRS7h (ORCPT ); Tue, 18 Jul 2017 14:59:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37434 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751675AbdGRS7f (ORCPT ); Tue, 18 Jul 2017 14:59:35 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 45907804F1 Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=mst@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 45907804F1 Date: Tue, 18 Jul 2017 21:59:33 +0300 From: "Michael S. Tsirkin" To: Jason Wang Cc: virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH net-next 2/5] virtio-net: pack headroom into ctx for mergeable buffer Message-ID: <20170718215432-mutt-send-email-mst@kernel.org> References: <1500295441-19339-1-git-send-email-jasowang@redhat.com> <1500295441-19339-3-git-send-email-jasowang@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1500295441-19339-3-git-send-email-jasowang@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Tue, 18 Jul 2017 18:59:35 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 17, 2017 at 08:43:58PM +0800, Jason Wang wrote: > Pack headroom into ctx, then during XDP set, we could know the size of > headroom and copy if needed. This is required for avoiding reset on > XDP. Not really when XDP is set - it's when buffers are used. virtio-net: pack headroom into ctx for mergeable buffers Pack headroom into ctx - this way when we get a buffer we can figure out the actual headroom that was allocated for the buffer. Will be helpful to optimize switching between XDP and non-XDP modes which have different headroom requirements. > > Signed-off-by: Jason Wang > --- > drivers/net/virtio_net.c | 29 ++++++++++++++++++++++++----- > 1 file changed, 24 insertions(+), 5 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 1f8c15c..8fae9a8 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -270,6 +270,23 @@ static void skb_xmit_done(struct virtqueue *vq) > netif_wake_subqueue(vi->dev, vq2txq(vq)); > } > > +#define MRG_CTX_HEADER_SHIFT 22 > +static void *mergeable_len_to_ctx(unsigned int truesize, > + unsigned int headroom) > +{ > + return (void *)(unsigned long)((headroom << MRG_CTX_HEADER_SHIFT) | truesize); > +} > + > +static unsigned int mergeable_ctx_to_headroom(void *mrg_ctx) > +{ > + return (unsigned long)mrg_ctx >> MRG_CTX_HEADER_SHIFT; > +} > + > +static unsigned int mergeable_ctx_to_truesize(void *mrg_ctx) > +{ > + return (unsigned long)mrg_ctx & ((1 << MRG_CTX_HEADER_SHIFT) - 1); > +} > + > /* Called from bottom half context */ > static struct sk_buff *page_to_skb(struct virtnet_info *vi, > struct receive_queue *rq, > @@ -639,13 +656,14 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, > } > rcu_read_unlock(); > > - if (unlikely(len > (unsigned long)ctx)) { > + truesize = mergeable_ctx_to_truesize(ctx); > + if (unlikely(len > truesize)) { > pr_debug("%s: rx error: len %u exceeds truesize %lu\n", > dev->name, len, (unsigned long)ctx); > dev->stats.rx_length_errors++; > goto err_skb; > } > - truesize = (unsigned long)ctx; > + > head_skb = page_to_skb(vi, rq, page, offset, len, truesize); > curr_skb = head_skb; > > @@ -665,13 +683,14 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, > } > > page = virt_to_head_page(buf); > - if (unlikely(len > (unsigned long)ctx)) { > + > + truesize = mergeable_ctx_to_truesize(ctx); > + if (unlikely(len > truesize)) { > pr_debug("%s: rx error: len %u exceeds truesize %lu\n", > dev->name, len, (unsigned long)ctx); > dev->stats.rx_length_errors++; > goto err_skb; > } > - truesize = (unsigned long)ctx; > > num_skb_frags = skb_shinfo(curr_skb)->nr_frags; > if (unlikely(num_skb_frags == MAX_SKB_FRAGS)) { > @@ -889,7 +908,7 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi, > > buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset; > buf += headroom; /* advance address leaving hole at front of pkt */ > - ctx = (void *)(unsigned long)len; > + ctx = mergeable_len_to_ctx(len, headroom); > get_page(alloc_frag->page); > alloc_frag->offset += len + headroom; > hole = alloc_frag->size - alloc_frag->offset; > -- > 2.7.4