{"id":2227984,"url":"http://patchwork.ozlabs.org/api/patches/2227984/?format=json","web_url":"http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260424162917.65725-1-mmc@linux.ibm.com/","project":{"id":2,"url":"http://patchwork.ozlabs.org/api/projects/2/?format=json","name":"Linux PPC development","link_name":"linuxppc-dev","list_id":"linuxppc-dev.lists.ozlabs.org","list_email":"linuxppc-dev@lists.ozlabs.org","web_url":"https://github.com/linuxppc/wiki/wiki","scm_url":"https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git","webscm_url":"https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/","list_archive_url":"https://lore.kernel.org/linuxppc-dev/","list_archive_url_format":"https://lore.kernel.org/linuxppc-dev/{}/","commit_url_format":"https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?id={}"},"msgid":"<20260424162917.65725-1-mmc@linux.ibm.com>","list_archive_url":"https://lore.kernel.org/linuxppc-dev/20260424162917.65725-1-mmc@linux.ibm.com/","date":"2026-04-24T16:29:17","name":"[v3] ibmveth: Disable GSO for packets with small MSS","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"21af75c23794aa4192913a6fede01adf646f226c","submitter":{"id":91298,"url":"http://patchwork.ozlabs.org/api/people/91298/?format=json","name":"Mingming Cao","email":"mmc@linux.ibm.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260424162917.65725-1-mmc@linux.ibm.com/mbox/","series":[{"id":501393,"url":"http://patchwork.ozlabs.org/api/series/501393/?format=json","web_url":"http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=501393","date":"2026-04-24T16:29:17","name":"[v3] ibmveth: Disable GSO for packets with small MSS","version":3,"mbox":"http://patchwork.ozlabs.org/series/501393/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2227984/comments/","check":"success","checks":"http://patchwork.ozlabs.org/api/patches/2227984/checks/","tags":{},"related":[],"headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linuxppc-dev@lists.ozlabs.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256\n header.s=pp1 header.b=ZMEyTdGE;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=112.213.38.117; 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Attempting to send such\npackets causes the adapter to freeze, stopping all traffic until\nmanually reset.\n\nImplement ndo_features_check to disable GSO for packets with small MSS\nvalues. The network stack will perform software segmentation instead.\n\nThe 224-byte minimum matches ibmvnic\ncommit (\"ibmvnic: Enforce stronger sanity checks\non GSO packets\")\nwhich uses the same physical adapters in SEA configurations.\n\nThe issue occurs specifically when the hardware attempts to perform\nsegmentation (gso_segs > 1) with a small MSS. Single-segment GSO packets\n(gso_segs == 1) do not trigger the problematic LSO code path and are\ntransmitted normally without segmentation.\n\nAdd an ndo_features_check callback to disable GSO when MSS < 224 bytes.\nAlso call vlan_features_check() to ensure proper handling of VLAN packets,\nparticularly QinQ (802.1ad) configurations where the hardware parser may\nnot support certain offload features.\n\nValidated using iptables to force small MSS values. Without the fix,\nthe adapter freezes. With the fix, packets are segmented in software\nand transmission succeeds. Comprehensive regression testing completedd \n(MSS tests, performance, stability).\n\nFixes: 8641dd85799f (\"ibmveth: Add support for TSO\")\nCc: stable@vger.kernel.org\nReviewed-by: Brian King \nTested-by: Shaik Abdulla \nTested-by: Naveed Ahmed \nSigned-off-by: Mingming Cao \n---\nChanges in v3:\n- Call vlan_features_check() to handle VLAN packets correctly\n- Clarified that gso_segs == 1 check is not needed for ibmveth\n (unlike ibmvnic, single-segment packets don't enter LSO path)\n- Updated commit message to explain the difference\n\nChanges in v2:\n- Add Fixes tag as requested by automated checks\n---\n drivers/net/ethernet/ibm/ibmveth.c | 22 ++++++++++++++++++++++\n drivers/net/ethernet/ibm/ibmveth.h | 1 +\n 2 files changed, 23 insertions(+)","diff":"diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c\nindex 58cc3147afe2..73e051d26b9d 100644\n--- a/drivers/net/ethernet/ibm/ibmveth.c\n+++ b/drivers/net/ethernet/ibm/ibmveth.c\n@@ -1756,6 +1756,27 @@ static int ibmveth_set_mac_addr(struct net_device *dev, void *p)\n \treturn 0;\n }\n \n+static netdev_features_t ibmveth_features_check(struct sk_buff *skb,\n+\t\t\t\t\t\tstruct net_device *dev,\n+\t\t\t\t\t\tnetdev_features_t features)\n+{\n+\t/* Some physical adapters do not support segmentation offload with\n+\t * MSS < 224. Disable GSO for such packets to avoid adapter freeze.\n+\t * Note: Single-segment packets (gso_segs == 1) don't need this check\n+\t * as they bypass the LSO path and are transmitted without segmentation.\n+\t */\n+\tif (skb_is_gso(skb)) {\n+\t\tif (skb_shinfo(skb)->gso_size < IBMVETH_MIN_LSO_MSS) {\n+\t\t\tnetdev_warn_once(dev,\n+\t\t\t\t\t \"MSS %u too small for LSO, disabling GSO\\n\",\n+\t\t\t\t\t skb_shinfo(skb)->gso_size);\n+\t\t\tfeatures &= ~NETIF_F_GSO_MASK;\n+\t\t}\n+\t}\n+\n+\treturn vlan_features_check(skb, features);\n+}\n+\n static const struct net_device_ops ibmveth_netdev_ops = {\n \t.ndo_open\t\t= ibmveth_open,\n \t.ndo_stop\t\t= ibmveth_close,\n@@ -1767,6 +1788,7 @@ static const struct net_device_ops ibmveth_netdev_ops = {\n \t.ndo_set_features\t= ibmveth_set_features,\n \t.ndo_validate_addr\t= eth_validate_addr,\n \t.ndo_set_mac_address = ibmveth_set_mac_addr,\n+\t.ndo_features_check\t= ibmveth_features_check,\n #ifdef CONFIG_NET_POLL_CONTROLLER\n \t.ndo_poll_controller\t= ibmveth_poll_controller,\n #endif\ndiff --git a/drivers/net/ethernet/ibm/ibmveth.h b/drivers/net/ethernet/ibm/ibmveth.h\nindex 068f99df133e..d87713668ed3 100644\n--- a/drivers/net/ethernet/ibm/ibmveth.h\n+++ b/drivers/net/ethernet/ibm/ibmveth.h\n@@ -37,6 +37,7 @@\n #define IBMVETH_ILLAN_IPV4_TCP_CSUM\t\t0x0000000000000002UL\n #define IBMVETH_ILLAN_ACTIVE_TRUNK\t\t0x0000000000000001UL\n \n+#define IBMVETH_MIN_LSO_MSS\t\t224\t/* Minimum MSS for LSO */\n /* hcall macros */\n #define h_register_logical_lan(ua, buflst, rxq, fltlst, mac) \\\n plpar_hcall_norets(H_REGISTER_LOGICAL_LAN, ua, buflst, rxq, fltlst, mac)\n","prefixes":["v3"]}