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GET /api/patches/2224102/?format=api
{ "id": 2224102, "url": "http://patchwork.ozlabs.org/api/patches/2224102/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260416191126.95336-1-mmc@linux.ibm.com/", "project": { "id": 2, "url": "http://patchwork.ozlabs.org/api/projects/2/?format=api", "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": "<20260416191126.95336-1-mmc@linux.ibm.com>", "list_archive_url": "https://lore.kernel.org/linuxppc-dev/20260416191126.95336-1-mmc@linux.ibm.com/", "date": "2026-04-16T19:11:26", "name": "[net] ibmveth: Disable GSO for packets with small MSS", "commit_ref": null, "pull_url": null, "state": "handled-elsewhere", "archived": false, "hash": "71c0d71a63202c021cbb093646dfc23d24dde40b", "submitter": { "id": 91298, "url": "http://patchwork.ozlabs.org/api/people/91298/?format=api", "name": "Mingming Cao", "email": "mmc@linux.ibm.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260416191126.95336-1-mmc@linux.ibm.com/mbox/", "series": [ { "id": 500197, "url": "http://patchwork.ozlabs.org/api/series/500197/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=500197", "date": "2026-04-16T19:11:26", "name": "[net] ibmveth: Disable GSO for packets with small MSS", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/500197/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2224102/comments/", "check": "success", "checks": "http://patchwork.ozlabs.org/api/patches/2224102/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "\n <linuxppc-dev+bounces-19815-incoming=patchwork.ozlabs.org@lists.ozlabs.org>", "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=avrXiipw;\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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lists.ozlabs.org;\n dmarc=pass (p=none dis=none) header.from=linux.ibm.com;\n dkim=pass (2048-bit key;\n unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256\n header.s=pp1 header.b=avrXiipw; dkim-atps=neutral;\n spf=pass (client-ip=148.163.158.5; helo=mx0b-001b2d01.pphosted.com;\n envelope-from=mmc@linux.ibm.com;\n receiver=lists.ozlabs.org) smtp.mailfrom=linux.ibm.com", "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc\n\t:content-transfer-encoding:date:from:message-id:mime-version\n\t:subject:to; s=pp1; bh=z9f2WoTgIfJ4Lt/PFrfw/gZW2lqfBvsWodpCT/WHv\n\tkY=; b=avrXiipwGhKKmW39TcCPg30LkOG54f34muqRGm9PQKGD3U4qYiolw8S74\n\t/k738qXbVJfx+lTJK2Q1yYZsIvx7F1ZLikPKddSDPwNdayFAwAUM4cNoAsYX5DtD\n\toNSUiH8jcfvUhUtuKGtA5Hb5+wVxXn1/hXaEXXpPjzNNLBAKUQcVc0akBIGLh4Rn\n\tthZslDrb/jILDxPwh9KneWVRBKJiARvQMG7rSrpcnPKWYlTU1FC97enDc/aCjYJU\n\tEI/OAh0fkOG0+VIhUz62GYPchdG4vrkoJFj4+Qw8aK5fVDAR7gJESRXvUNo650ix\n\tuVlLj8tZl3LMYpgZfFZqL7rKFQ1Dg==", "From": "Mingming Cao <mmc@linux.ibm.com>", "To": "netdev@vger.kernel.org", "Cc": "davem@davemloft.net, kuba@kernel.org, edumazet@google.com,\n pabeni@redhat.com, horms@kernel.org, bjking1@linux.ibm.com,\n haren@linux.ibm.com, ricklind@linux.ibm.com, maddy@linux.ibm.com,\n mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org,\n stable@vger.kernel.org, Mingming Cao <mmc@linux.ibm.com>,\n Shaik Abdulla <shaik.abdulla1@ibm.com>,\n Naveed Ahmed <naveedaus@in.ibm.com>", "Subject": "[PATCH net] ibmveth: Disable GSO for packets with small MSS", "Date": "Thu, 16 Apr 2026 12:11:26 -0700", "Message-Id": "<20260416191126.95336-1-mmc@linux.ibm.com>", "X-Mailer": "git-send-email 2.39.3 (Apple Git-146)", "X-Mailing-List": "linuxppc-dev@lists.ozlabs.org", "List-Id": "<linuxppc-dev.lists.ozlabs.org>", "List-Help": "<mailto:linuxppc-dev+help@lists.ozlabs.org>", "List-Owner": "<mailto:linuxppc-dev+owner@lists.ozlabs.org>", "List-Post": "<mailto:linuxppc-dev@lists.ozlabs.org>", "List-Archive": "<https://lore.kernel.org/linuxppc-dev/>,\n <https://lists.ozlabs.org/pipermail/linuxppc-dev/>", "List-Subscribe": "<mailto:linuxppc-dev+subscribe@lists.ozlabs.org>,\n <mailto:linuxppc-dev+subscribe-digest@lists.ozlabs.org>,\n <mailto:linuxppc-dev+subscribe-nomail@lists.ozlabs.org>", "List-Unsubscribe": "<mailto:linuxppc-dev+unsubscribe@lists.ozlabs.org>", "Precedence": "list", "MIME-Version": "1.0", "Content-Transfer-Encoding": "8bit", "X-TM-AS-GCONF": "00", "X-Proofpoint-Reinject": "loops=2 maxloops=12", "X-Proofpoint-GUID": "ioZ6CX6QVo8vsH9VSgrCPNanekD26vNx", "X-Proofpoint-ORIG-GUID": "k_DCrsCbumqLIMI8Bp7BTxOvzEMclNFT", "X-Authority-Analysis": "v=2.4 cv=WbE8rUhX c=1 sm=1 tr=0 ts=69e13468 cx=c_pps\n a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17\n a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22\n a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8\n a=13N5Qnvyu_7Mey2fMVwA:9", "X-Proofpoint-Spam-Details-Enc": "AW1haW4tMjYwNDE2MDE3OSBTYWx0ZWRfX/0y1W4SeUqxY\n 51RRBnHeeKIcG81i5wocxedY6jBrgo9Eq2WgPnFZEHJKc+gf9KbJyxQ8Z6Pg3xXKcA/5WxcGoBu\n BldGT2AeBY79mo2pccex8AyuIh7dFSmu4p1fJXb1VxWucqq/LHLI2hUIU8ASvH4KlW07SgqrYFQ\n SNTkSepegJSMDSRvVqVj6fYLA21lKiqwX/lbuQfFSlMdYKzRYChCodN9okvq6YAMCgXyaL+rQZu\n Z/rnurdgpRTKR9k1Pb4hx7xjMU4tO/jTepCJOMs8A2cqxRux43CPKWpVkPBt2ipD/RMatO0OhY/\n vm/a2g0Z9/8tHOLznicT4Y7LnrlNMZ7IdwpjPy2oIo4PLgqjcVw5pf4BxGM6jGrjD+y/3++F3wC\n TUtjY+9p/15t2NutPp2Bn/F2Lozu3h1vz7JbaQv82nEcqzgXEVOjRk8qXTy47YIk57F6Jyr4CSb\n EdIS3DFDK2qRRnc3RGQ==", "X-Proofpoint-Virus-Version": "vendor=baseguard\n engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49\n definitions=2026-04-16_03,2026-04-16_03,2025-10-01_01", "X-Proofpoint-Spam-Details": "rule=outbound_notspam policy=outbound score=0\n suspectscore=0 bulkscore=0 priorityscore=1501 spamscore=0 clxscore=1011\n phishscore=0 impostorscore=0 adultscore=0 malwarescore=0 lowpriorityscore=0\n classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0\n reason=mlx scancount=1 engine=8.22.0-2604070000 definitions=main-2604160179", "X-Spam-Status": "No, score=-0.7 required=3.0 tests=DKIM_SIGNED,DKIM_VALID,\n\tRCVD_IN_DNSWL_LOW,RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,\n\tSPF_PASS autolearn=disabled version=4.0.1 OzLabs 8", "X-Spam-Checker-Version": "SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org" }, "content": "Some physical adapters on Power systems do not support segmentation\noffload when the MSS is less than 224 bytes. 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 <f10b09ef687f> (\"ibmvnic: Enforce stronger sanity checks\non GSO packets\")\nwhich uses the same physical adapters in SEA configurations.\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.\n\nCc: stable@vger.kernel.org\nReviewed-by: Brian King <bjking1@linux.ibm.com>\nTested-by: Shaik Abdulla <shaik.abdulla1@ibm.com>\nTested-by: Naveed Ahmed <naveedaus@in.ibm.com>\nSigned-off-by: Mingming Cao <mmc@linux.ibm.com>\n---\n drivers/net/ethernet/ibm/ibmveth.c | 20 ++++++++++++++++++++\n drivers/net/ethernet/ibm/ibmveth.h | 1 +\n 2 files changed, 21 insertions(+)", "diff": "diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c\nindex 58cc3147afe2..7935c9384ef4 100644\n--- a/drivers/net/ethernet/ibm/ibmveth.c\n+++ b/drivers/net/ethernet/ibm/ibmveth.c\n@@ -1756,6 +1756,25 @@ 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 */\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 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 +1786,7 @@ 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": [ "net" ] }