Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752613AbdHRNS1 (ORCPT ); Fri, 18 Aug 2017 09:18:27 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:55727 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752931AbdHRNPy (ORCPT ); Fri, 18 Aug 2017 09:15:54 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Michael S. Tsirkin" Date: Fri, 18 Aug 2017 14:13:20 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 122/134] virtio_net: fix support for small rings In-Reply-To: X-SA-Exim-Connect-IP: 82.70.136.246 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3703 Lines: 111 3.16.47-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: "Michael S. Tsirkin" commit d85b758f72b05a774045545f24d70980e3e9aac4 upstream. When ring size is small (<32 entries) making buffers smaller means a full ring might not be able to hold enough buffers to fit a single large packet. Make sure a ring full of buffers is large enough to allow at least one packet of max size. Fixes: 2613af0ed18a ("virtio_net: migrate mergeable rx buffers to page frag allocators") Signed-off-by: Michael S. Tsirkin [bwh: Backported to 3.16: - There's no net_device::max_mtu, so always set packet_len = IP_MAX_MTU - Adjust context] Signed-off-by: Ben Hutchings --- drivers/net/virtio_net.c | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-) --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -27,6 +27,7 @@ #include #include #include +#include static int napi_weight = NAPI_POLL_WEIGHT; module_param(napi_weight, int, 0444); @@ -92,6 +93,9 @@ struct receive_queue { /* RX: fragments + linear part + virtio header */ struct scatterlist sg[MAX_SKB_FRAGS + 2]; + /* Min single buffer size for mergeable buffers case. */ + unsigned int min_buf_len; + /* Name of this receive queue: input.$index */ char name[40]; }; @@ -600,13 +604,14 @@ static int add_recvbuf_big(struct receiv return err; } -static unsigned int get_mergeable_buf_len(struct ewma *avg_pkt_len) +static unsigned int get_mergeable_buf_len(struct receive_queue *rq, + struct ewma *avg_pkt_len) { const size_t hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf); unsigned int len; len = hdr_len + clamp_t(unsigned int, ewma_read(avg_pkt_len), - GOOD_PACKET_LEN, PAGE_SIZE - hdr_len); + rq->min_buf_len - hdr_len, PAGE_SIZE - hdr_len); return ALIGN(len, MERGEABLE_BUFFER_ALIGN); } @@ -618,7 +623,7 @@ static int add_recvbuf_mergeable(struct int err; unsigned int len, hole; - len = get_mergeable_buf_len(&rq->mrg_avg_pkt_len); + len = get_mergeable_buf_len(rq, &rq->mrg_avg_pkt_len); if (unlikely(!skb_page_frag_refill(len, alloc_frag, gfp))) return -ENOMEM; @@ -1462,6 +1467,21 @@ static void virtnet_del_vqs(struct virtn virtnet_free_queues(vi); } +/* How large should a single buffer be so a queue full of these can fit at + * least one full packet? + * Logic below assumes the mergeable buffer header is used. + */ +static unsigned int mergeable_min_buf_len(struct virtnet_info *vi, struct virtqueue *vq) +{ + const unsigned int hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf); + unsigned int rq_size = virtqueue_get_vring_size(vq); + unsigned int packet_len = IP_MAX_MTU; + unsigned int buf_len = hdr_len + ETH_HLEN + VLAN_HLEN + packet_len; + unsigned int min_buf_len = DIV_ROUND_UP(buf_len, rq_size); + + return max(min_buf_len, hdr_len); +} + static int virtnet_find_vqs(struct virtnet_info *vi) { vq_callback_t **callbacks; @@ -1517,6 +1537,7 @@ static int virtnet_find_vqs(struct virtn for (i = 0; i < vi->max_queue_pairs; i++) { vi->rq[i].vq = vqs[rxq2vq(i)]; + vi->rq[i].min_buf_len = mergeable_min_buf_len(vi, vi->rq[i].vq); vi->sq[i].vq = vqs[txq2vq(i)]; } @@ -1601,7 +1622,8 @@ static ssize_t mergeable_rx_buffer_size_ BUG_ON(queue_index >= vi->max_queue_pairs); avg = &vi->rq[queue_index].mrg_avg_pkt_len; - return sprintf(buf, "%u\n", get_mergeable_buf_len(avg)); + return sprintf(buf, "%u\n", + get_mergeable_buf_len(&vi->rq[queue_index], avg)); } static struct rx_queue_attribute mergeable_rx_buffer_size_attribute =