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Mon, 23 Mar 2026 15:01:49 +0000 (GMT) From: Omar Elghoul To: vishs@meta.com Cc: andrew+netdev@lunn.ch, davem@davemloft.net, dw@davidwei.uk, edumazet@google.com, eperezma@redhat.com, ilias.apalodimas@linaro.org, jasowang@redhat.com, kernel-team@meta.com, kuba@kernel.org, linux-kernel@vger.kernel.org, mst@redhat.com, netdev@vger.kernel.org, pabeni@redhat.com, technoboy85@gmail.com, virtualization@lists.linux.dev, xuanzhuo@linux.alibaba.com, oelghoul@linux.ibm.com Subject: Re: [PATCH net-next v11] virtio_net: add page_pool support for buffer allocation Date: Mon, 23 Mar 2026 11:01:31 -0400 Message-ID: <20260323150136.14452-1-oelghoul@linux.ibm.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260310183107.2822016-1-vishs@meta.com> References: <20260310183107.2822016-1-vishs@meta.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: YNzfoRIt1da90gDrXm5OnayrwaK83DCr X-Authority-Analysis: v=2.4 cv=aMr9aL9m c=1 sm=1 tr=0 ts=69c155e0 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=bD6ukYfIgYhu4hH-dYIA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzIzMDExNCBTYWx0ZWRfXx63mzxnELWk5 Y4ei4W1R77ANzeQcp3sM/IdvojFh1xZob0caVE4n47QoppYM048+qJ2ITChKBSjII++GBT3OduH FgKkCoVxgd/db9ymu20dPIn9V/fyFxZfEySwE7z7hPyZR7l5xim0s4c4dVCS+N4BKVnI0PKq1tu Q3VQWOb3aJI8NTpl0kqw2nVIfI4hH6gS0tAJE+FsJSdcnGj/vEHnHX9NDmGpag2zyjCd9wBIjTE fhXgeZWkW+1b4vyW4wli182xMcnpU+FO4qTWf9OumG1AmNrAySfCqOPfmEyY59nOzJZ2u78X1Gx I6XRcQvrlpEGEqFM3P2lTFIVTn9VhSM4BgUrpwdcKGDc2GQzwp7UwpwdFBViTmSGMeMWni8GmZb /2ruwN8yuID2OV1fr4NADUTfUJFtlWYlHu235M+UQXNnadxH8kilKOKn4kO6vGzuVpUVYQbRz18 7oLM2n8sWdX/X/s4bvg== X-Proofpoint-GUID: 9gD9_WOZoQLsJS8lan0dhb2SdmUj0w89 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-23_04,2026-03-23_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 lowpriorityscore=0 adultscore=0 impostorscore=0 malwarescore=0 suspectscore=0 phishscore=0 priorityscore=1501 bulkscore=0 clxscore=1011 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603230114 Hi, I've been testing linux-next (tags later than 03/17) and hit new issues in virtio-net on s390x. I bisected the issue, and I found this patch to be the first buggy commit. The issue seems to only be reproducible when running in Secure Execution. Tested in a KVM guest, the virtio-net performance appears greatly reduced, and the dmesg output shows many instances of the following error messages. Partial relevant logs ===================== [   49.332028] macvtap0: bad gso: type: 0, size: 0, flags 1 tunnel 0 tnl csum 0 [   74.365668] macvtap0: bad gso: type: 2e, size: 27948, flags 0 tunnel 0 tnl csum 0 [  403.302168] macvtap0: bad csum: flags: 2, gso_type: 23 rx_tnl_csum 0 [  403.302271] macvtap0: bad csum: flags: 2, gso_type: e0 rx_tnl_csum 0 [  403.302279] macvtap0: bad csum: flags: 2, gso_type: e1 rx_tnl_csum 0 [  403.309492] macvtap0: bad csum: flags: 2, gso_type: 4c rx_tnl_csum 0 [  403.317029] macvtap0: bad csum: flags: 2, gso_type: e0 rx_tnl_csum 0 Steps to reproduce ================== 1. Boot a Linux guest implementing this patch under QEMU/KVM (*) with SE enabled and a virtio-net-ccw device attached. 2. Run dmesg. The error message is usually already present at boot time, but if not, it can be reproduced by creating any network traffic. (*) This patch was not tested in a non-KVM hypervisor environment. I've further confirmed that reverting this patch onto its parent commit resolves the issue. Please let me know if you'd like me to test a fix or if you would need more information. Thanks in advance. 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Mon, 23 Mar 2026 15:01:49 +0000 (GMT) To: vishs@meta.com Cc: andrew+netdev@lunn.ch, davem@davemloft.net, dw@davidwei.uk, edumazet@google.com, eperezma@redhat.com, ilias.apalodimas@linaro.org, jasowang@redhat.com, kernel-team@meta.com, kuba@kernel.org, linux-kernel@vger.kernel.org, mst@redhat.com, netdev@vger.kernel.org, pabeni@redhat.com, technoboy85@gmail.com, virtualization@lists.linux.dev, xuanzhuo@linux.alibaba.com, oelghoul@linux.ibm.com Subject: Re: [PATCH net-next v11] virtio_net: add page_pool support for buffer allocation Date: Mon, 23 Mar 2026 11:01:31 -0400 Message-ID: <20260323150136.14452-1-oelghoul@linux.ibm.com> In-Reply-To: <20260310183107.2822016-1-vishs@meta.com> References: <20260310183107.2822016-1-vishs@meta.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: YNzfoRIt1da90gDrXm5OnayrwaK83DCr X-Authority-Analysis: v=2.4 cv=aMr9aL9m c=1 sm=1 tr=0 ts=69c155e0 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=bD6ukYfIgYhu4hH-dYIA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzIzMDExNCBTYWx0ZWRfXx63mzxnELWk5 Y4ei4W1R77ANzeQcp3sM/IdvojFh1xZob0caVE4n47QoppYM048+qJ2ITChKBSjII++GBT3OduH FgKkCoVxgd/db9ymu20dPIn9V/fyFxZfEySwE7z7hPyZR7l5xim0s4c4dVCS+N4BKVnI0PKq1tu Q3VQWOb3aJI8NTpl0kqw2nVIfI4hH6gS0tAJE+FsJSdcnGj/vEHnHX9NDmGpag2zyjCd9wBIjTE fhXgeZWkW+1b4vyW4wli182xMcnpU+FO4qTWf9OumG1AmNrAySfCqOPfmEyY59nOzJZ2u78X1Gx I6XRcQvrlpEGEqFM3P2lTFIVTn9VhSM4BgUrpwdcKGDc2GQzwp7UwpwdFBViTmSGMeMWni8GmZb /2ruwN8yuID2OV1fr4NADUTfUJFtlWYlHu235M+UQXNnadxH8kilKOKn4kO6vGzuVpUVYQbRz18 7oLM2n8sWdX/X/s4bvg== X-Proofpoint-GUID: 9gD9_WOZoQLsJS8lan0dhb2SdmUj0w89 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-23_04,2026-03-23_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 lowpriorityscore=0 adultscore=0 impostorscore=0 malwarescore=0 suspectscore=0 phishscore=0 priorityscore=1501 bulkscore=0 clxscore=1011 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603230114 X-MIME-Autoconverted: from 8bit to quoted-printable by mx0a-001b2d01.pphosted.com id 62MNU57e670670 X-Mimecast-Spam-Score: 2 X-Mimecast-MFC-PROC-ID: yBtnEdeN2-qRS_8RwN-A2v8dOKEychym13QMC4ypmuE_1774278139 X-Mimecast-Impersonation-Protect: Policy=DMARC Check - CHG0118091;Similar Internal Domain=false;Similar Monitored External Domain=false;Custom External Domain=false;Mimecast External Domain=false;Newly Observed Domain=false;Internal User Name=false;Custom Display Name List=false;Reply-to Address Mismatch=false;Targeted Threat Dictionary=false;Mimecast Threat Dictionary=false;Custom Threat Dictionary=false X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition;Similar Internal Domain=false;Similar Monitored External Domain=false;Custom External Domain=false;Mimecast External Domain=false;Newly Observed Domain=false;Internal User Name=false;Custom Display Name List=false;Reply-to Address Mismatch=false;Targeted Threat Dictionary=false;Mimecast Threat Dictionary=false;Custom Threat Dictionary=false Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Message-ID: <20260323150131.aUoYFKJ-3zhMODd7QgjU17JXBX4iy21Emo07p6-waKI@z> Hi, I've been testing linux-next (tags later than 03/17) and hit new issues in virtio-net on s390x. I bisected the issue, and I found this patch to be the first buggy commit. The issue seems to only be reproducible when running in Secure Execution. Tested in a KVM guest, the virtio-net performance appears greatly reduced, and the dmesg output shows many instances of the following error messages. Partial relevant logs =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D [ =C2=A0 49.332028] macvtap0: bad gso: type: 0, size: 0, flags 1 tunnel 0 t= nl csum 0 [ =C2=A0 74.365668] macvtap0: bad gso: type: 2e, size: 27948, flags 0 tunne= l 0 tnl csum 0 [=C2=A0 403.302168] macvtap0: bad csum: flags: 2, gso_type: 23 rx_tnl_csum = 0 [=C2=A0 403.302271] macvtap0: bad csum: flags: 2, gso_type: e0 rx_tnl_csum = 0 [=C2=A0 403.302279] macvtap0: bad csum: flags: 2, gso_type: e1 rx_tnl_csum = 0 [=C2=A0 403.309492] macvtap0: bad csum: flags: 2, gso_type: 4c rx_tnl_csum = 0 [=C2=A0 403.317029] macvtap0: bad csum: flags: 2, gso_type: e0 rx_tnl_csum = 0 Steps to reproduce =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D 1. Boot a Linux guest implementing this patch under QEMU/KVM (*) with SE enabled and a virtio-net-ccw device attached. 2. Run dmesg. The error message is usually already present at boot time, but if not, it can be reproduced by creating any network traffic. (*) This patch was not tested in a non-KVM hypervisor environment. I've further confirmed that reverting this patch onto its parent commit resolves the issue. Please let me know if you'd like me to test a fix or if you would need more information. Thanks in advance. Best, Omar